zfs: merge openzfs/zfs@a03ebd9be

[FreeBSD/FreeBSD.git] / UPDATING

Updating Information for users of FreeBSD-CURRENT.

This file is maintained and copyrighted by M. Warner Losh <imp@freebsd.org>.
See end of file for further details.  For commonly done items, please see the
COMMON ITEMS: section later in the file.  These instructions assume that you
basically know what you are doing.  If not, then please consult the FreeBSD
handbook:

    https://docs.freebsd.org/en/books/handbook/cutting-edge/#makeworld

Items affecting the ports and packages system can be found in
/usr/ports/UPDATING.  Please read that file before updating system packages
and/or ports.

NOTE TO PEOPLE WHO THINK THAT FreeBSD 15.x IS SLOW:
        FreeBSD 15.x has many debugging features turned on, in both the kernel
        and userland.  These features attempt to detect incorrect use of
        system primitives, and encourage loud failure through extra sanity
        checking and fail stop semantics.  They also substantially impact
        system performance.  If you want to do performance measurement,
        benchmarking, and optimization, you'll want to turn them off.  This
        includes various WITNESS- related kernel options, INVARIANTS, malloc
        debugging flags in userland, and various verbose features in the
        kernel.  Many developers choose to disable these features on build
        machines to maximize performance.  (To completely disable malloc
        debugging, define WITH_MALLOC_PRODUCTION in /etc/src.conf and rebuild
        world, or to merely disable the most expensive debugging functionality
        at runtime, run "ln -s 'abort:false,junk:false' /etc/malloc.conf".)

20231120:
        If you have an arm64 system that uses ACPI, you will need to update your
        loader.efi in the ESP when you update past this point.  Detection of ACPI
        was moved earlier in the binary so the scripts could use it, but old
        binaries don't have this, so we default to 'no ACPI' in this case. You can
        undisable ACPI by doing
                OK unset hint.acpi.0.disabled
        This can also be used to recover any other system that was updated in the
        small window where amd64 was also broken.

20231113:
        The WITHOUT_LLD_IS_LD option has been removed.  When LLD is enabled
        it is always installed as /usr/bin/ld.

20231027:
        Forward compatibility (running the new code on old kernels) for the
        "ino64" project have been removed. The need for it has passed long ago.

20231018:
        Commit 57ce37f9dcd0 changed the internal KAPI between the
        nfscommon and nfscl modules.  Both must be rebuilt from sources.

20231010:
        dialog(1) has been replaced in base by bsddialog(1), while most of the
        time replacing a dialog(1) call by a bsddialog(1) call works out of the
        box, bsddialog(1) is not considered as a drop-in replacement for
        dialog(1).

        If you do depend on dialog(1) functionality, please install cdialog
        from ports:

        pkg install cdialog

20230927:
        The EARLY_AP_STARTUP kernel option is mandatory on x86.  The option
        has been added to DEFAULTS, so it should automatically be included in
        custom kernel configurations without any additional change.

20230922:
        A new loader tunable net.pf.default_to_drop allows pf(4)’s default
        behaviour to be changed from pass to drop. Previously this required
        recompiling the kernel with the option PF_DEFAULT_TO_DROP.

20230914:
        Enable splitting out pkgbase manpages into separate packages by
        default. To disable this, set WITHOUT_MANSPLITPKG=yes in src.conf.

20230911:
        Move standard include files to the clibs-dev package and move clang
        internal libraries and headers to clang and clang-dev. Upgrading systems
        installed using pkgbase past this change involves extra steps to allow
        for these file moves:

                pkg upgrade -y FreeBSD-utilities
                pkg upgrade -y FreeBSD-utilities-dev
                pkg upgrade -y

20230909:
        Enable vnet sysctl variables to be loader tunable. SYSCTLs which
        belongs to VNETs can be initialized during early boot or module
        loading if they are marked with CTLFLAG_TUN and there are
        corresponding kernel environment variables.

20230901:
        The WITH_INIT_ALL_PATTERN and WITH_INIT_ALL_ZERO build options have
        been replaced by INIT_ALL=pattern and INIT_ALL=zero respectively.

20230824:
        FreeBSD 15.0-CURRENT.

20230817:
        Serial communication (in boot loaders, kernel, and userland) has
        been changed to default to 115200 bps, in line with common industry
        practice and typcial firmware serial console redirection
        configuration.

        Note that the early x86 BIOS bootloader (i.e., boot0sio) does not
        support rates above 9600 bps and is not changed. boot0sio users may
        set BOOT_COMCONSOLE_SPEED=9600 to use 9600 for all of the boot
        components, or use the standard boot0 and have the boot2 stage start
        with the serial port at 115200.

20230807:
        Following the general removal of MIPS support, the ath(4) AHB bus-
        frontend has been removed, too, and building of the PCI support is
        integrated with the ath(4) main module again. As a result, there's
        no longer a need for if_ath_pci_load="YES" in /boot/loader.conf or
        "device ath_pci" in the kernel configuration.

20230803:
        MAXCPU has been increased to 1024 in the amd64 GENERIC kernel config.
        Out-of-tree kernel modules will need to be rebuilt.

20230724:
        CAM has been mechanically updated s/u_int(64|32|16|8)_t/uint\1_t/g
        to move to the standard uintXX_t types from the old, traditional
        BSD u_intXX_t types. This should be a NOP, but may cause problems
        for out of tree changes. The SIMs were not updated since most of
        the old u_intXX_t uses weren't due to CAM interfaces.

20230713:
        stable/14 branch created.

20230629:
        The heuristic for detecting old chromebooks with an EC bug that requires
        atkbdc driver workarounds has changed. There should be no functional
        change, but if your old chromebook's keyboard stops working, please
        file a PR and assign it to imp.

20230623:
        OpenSSL has been updated to version 3.0, including changes throughout
        the base system.  It is important to rebuild third-party software
        after upgrading.

20230619:
        To enable pf rdr rules for connections initiated from the host, pf
        filter rules can be optionally enabled for packets delivered
        locally. This can change the behavior of rules which match packets
        delivered to lo0. To enable this feature:

                sysctl net.pf.filter_local=1
                service pf restart

        When enabled, its best to ensure that packets delivered locally are not
        filtered, e.g. by adding a 'skip on lo' rule.

20230613:
        Improvements to libtacplus(8) mean that tacplus.conf(5) now
        follows POSIX shell syntax rules. This may cause TACACS+
        authentication to fail if the shared secret contains a single
        quote, double quote, or backslash character which isn't
        already properly quoted or escaped.

20230612:
        Belatedly switch the default nvme block device on x86 from nvd to nda.
        nda created nvd compatibility links by default, so this should be a
        nop. If this causes problems for your application, set hw.nvme.use_nvd=1
        in your loader.conf or add `options NVME_USE_NVD=1` to your kernel
        config. To disable the nvd compatibility aliases, add
        kern.cam.nda.nvd_compat=0 to loader.conf.  The default has been nda on
        all non-x86 platforms for some time now. If you need to fall back,
        please email imp@freebsd.org about why.

        Encrypted swap partitions need to be changed from nvd to nda if you
        migrate, or you need to use the above to switch back to nvd.

20230422:
        Remove portsnap(8).  Users are encouraged to obtain the ports tree
        using git instead.

20230420:
        Add jobs.mk to save typing. Enables -j${JOB_MAX} and logging
        eg.
                make buildworld-jobs
        runs
                make -j${JOB_MAX} buildworld > ../buildworld.log 2>&1

        where JOB_MAX is derrived from ncpus in local.sys.mk if not set in env.

20230316:
        Video related devices for some arm devices have been renamed.
        If you have a custom kernel config and want to use hdmi output on
        IMX6 board you need to add "device dwc_hdmi" "device imx6_hdmi" and
        "device imx6_ipu" to it.
        If you have a custom kernel config and want to use hdmi output on
        TI AM335X board you need to add "device tda19988" to it.
        If you add "device hdmi" in it you need to remove it as it doesn't
        exist anymore.

20230221:
        Introduce new kernel options KBD_DELAY1 and KBD_DELAY2. See atkbdc(4)
        for details.

20230206:
        sshd now defaults to having X11Forwarding disabled, following upstream.
        Administrators who wish to enable X11Forwarding should add
        `X11Forwarding yes` to /etc/ssh/sshd_config.

20230204:
        Since commit 75d41cb6967 Huawei 3G/4G LTE Mobile Devices do not default
        to ECM, but NCM mode and need u3g and ucom modules loaded. See cdce(4).

20230130:
        As of commit 7c40e2d5f685, the dependency on netlink(4) has been added
        to the linux_common(4) module. Users relying on linux_common may need
        to complile netlink(4) module if it is not present in their kernel.

20230126:
        The WITHOUT_CXX option has been removed. C++ components in the base
        system are now built unconditionally.

20230113:
        LinuxKPI pci.h changes may require out-of-tree drivers to be recompiled.
        Bump _FreeBSD_version to 1400078 to be able to detect this change.

20221212:
        llvm-objump is now always installed as objdump.  Previously there was
        no /usr/bin/objdump unless the WITH_LLVM_BINUTILS knob was used.

        Some LLVM objdump options have a different output format compared to
        GNU objdump; readelf is available for inspecting ELF files, and GNU
        objdump is available from the devel/binutils port or package.

20221205:
        dma(8) has replaced sendmail(8) as the default mta.  For people willing
        to reenable sendmail(8):

        $ cp /usr/share/examples/sendmail/mailer.conf /etc/mail/mailer.conf

        and add sendmail_enable="YES" to rc.conf.

20221204:
        hw.bus.disable_failed_devices has changed from 'false' to 'true' by
        default. Now if newbus succeeds in probing a device, but fails to attach
        the device, we'll disable the device. In the past, we'd keep retrying
        the device on each new driver loaded. To get that behavior now, one
        needs to use devctl to re-enable the device, and reprobe it (or set
        the sysctl/tunable hw.bus.disable_failed_devices=false).

        NOTE: This was reverted 20221205 due to unexpected compatibility issues

20221122:
        pf no longer accepts 'scrub fragment crop' or 'scrub fragment drop-ovl'.
        These configurations are no longer automatically reinterpreted as
        'scrub fragment reassemble'.

20221121:
        The WITHOUT_CLANG_IS_CC option has been removed.  When Clang is enabled
        it is always installed as /usr/bin/cc (and c++, cpp).

20221026:
        Some programs have been moved into separate packages. It is recommended
        for pkgbase users to do:

        pkg install FreeBSD-dhclient FreeBSD-geom FreeBSD-resolvconf \
          FreeBSD-devd FreeBSD-devmatch

        after upgrading to restore all the component that were previously
        installed.

20221002:
        OPIE has been removed from the base system.  If needed, it can
        be installed from ports (security/opie) or packages (opie).
        Otherwise, make sure that your PAM policies do not reference
        pam_opie or pam_opieaccess.

20220610:
        LinuxKPI pm.h changes require an update to the latest drm-kmod version
        before re-compiling to avoid errors.

20211230:
        The macros provided for the manipulation of CPU sets (e.g. CPU_AND)
        have been modified to take 2 source arguments instead of only 1.
        Externally maintained sources that use these macros will have to
        be adapted. The FreeBSD version has been bumped to 1400046 to
        reflect this change.

20211214:
        A number of the kernel include files are able to be included by
        themselves.  A test has been added to buildworld to enforce this.

20211209:
        Remove mips as a recognized target. This starts the decommissioning of
        mips support in FreeBSD. mips related items will be removed wholesale in
        the coming days and weeks.

        This broke the NO_CLEAN build for some people. Either do a clean build
        or touch
                lib/clang/include/llvm/Config/Targets.def
                lib/clang/include/llvm/Config/AsmParsers.def
                lib/clang/include/llvm/Config/Disassemblers.def
                lib/clang/include/llvm/Config/AsmPrinters.def
        before the build to force everything to rebuild that needs to.

20211202:
        Unbound support for RFC8375: The special-use domain 'home.arpa' is
        by default blocked. To unblock it use a local-zone nodefault
        statement in unbound.conf:
                local-zone: "home.arpa." nodefault

        Or use another type of local-zone to override with your choice.

        The reason for this is discussed in Section 6.1 of RFC8375:
        Because 'home.arpa.' is not globally scoped and cannot be secured
        using DNSSEC based on the root domain's trust anchor, there is no way
        to tell, using a standard DNS query, in which homenet scope an answer
        belongs.  Consequently, users may experience surprising results with
        such names when roaming to different homenets.

20211110:
        Commit b8d60729deef changed the TCP congestion control framework so
        that any of the included congestion control modules could be
        the single module built into the kernel. Previously newreno
        was automatically built in through direct reference. As of
        this commit you are required to declare at least one congestion
        control module (e.g. 'options CC_NEWRENO') and to also declare a
        default using the CC_DEFAULT option (e.g. options CC_DEFAULT="newreno\").
        The GENERIC configuration includes CC_NEWRENO and defines newreno
        as the default. If no congestion control option is built into the
        kernel and you are including networking, the kernel compile will
        fail. Also if no default is declared the kernel compile will fail.

20211118:
        Mips has been removed from universe builds. It will be removed from the
        tree shortly.

20211106:
        Commit f0c9847a6c47 changed the arguments for VOP_ALLOCATE.
        The NFS modules must be rebuilt from sources and any out
        of tree file systems that implement their own VOP_ALLOCATE
        may need to be modified.

20211022:
        The synchronous PPP kernel driver sppp(4) has been removed.
        The cp(4) and ce(4) drivers are now always compiled with netgraph(4)
        support, formerly enabled by NETGRAPH_CRONYX option.

20211020:
        sh(1) is now the default shell for the root user.  To force root to use
        the csh shell, please run the following command as root:

        # chsh -s csh

20211004:
        Ncurses distribution has been split between libtinfow and libncurses
        with libncurses.so becoming a linker (ld) script to seamlessly link
        to libtinfow as needed. Bump _FreeBSD_version to 1400035 to reflect
        this change.

20210923:
        As of commit 8160a0f62be6, the dummynet module no longer depends on the
        ipfw module. Dummynet can now be used by pf as well as ipfw. As such
        users who relied on this dependency may need to include ipfw in the
        list of modules to load on their systems.

20210922:
        As of commit 903873ce1560, the mixer(8) utility has got a slightly
        new syntax. Please refer to the mixer(8) manual page for more
        information. The old mixer utility can be installed from ports:
        audio/freebsd-13-mixer

20210911:
        As of commit 55089ef4f8bb, the global variable nfs_maxcopyrange has
        been deleted from the nfscommon.ko.  As such, nfsd.ko must be built
        from up to date sources to avoid an undefined reference when
        being loaded.

20210817:
        As of commit 62ca9fc1ad56 OpenSSL no longer enables kernel TLS
        by default.  Users can enable kernel TLS via the "KTLS" SSL
        option.  This can be enabled globally by using a custom
        OpenSSL config file via OPENSSL_CONF or via an
        application-specific configuration option for applications
        which permit setting SSL options via SSL_CONF_cmd(3).

20210811:
        Commit 3ad1e1c1ce20 changed the internal KAPI between the NFS
        modules. Therefore, all need to be rebuilt from sources.

20210730:
        Commit b69019c14cd8 removes pf's DIOCGETSTATESNV ioctl.
        As of be70c7a50d32 it is no longer used by userspace, but it does mean
        users may not be able to enumerate pf states if they update the kernel
        past b69019c14cd8 without first updating userspace past be70c7a50d32.

20210729:
        As of commit 01ad0c007964 if_bridge member interfaces can no longer
        change their MTU. Changing the MTU of the bridge itself will change the
        MTU on all member interfaces instead.

20210716:
        Commit ee29e6f31111 changed the internal KAPI between the nfscommon
        and nfsd modules. Therefore, both need to be rebuilt from sources.
        Bump __FreeBSD_version to 1400026 for this KAPI change.

20210715:
        The 20210707 awk update brought in a change in behavior. This has
        been corrected as of d4d252c49976. Between these dates, if you
        installed a new awk binary, you may not be able to build a new
        kernel because the change in behavior affected the genoffset
        script used to build the kernel. If you did update, the fix is
        to update your sources past the above hash and do
                % cd usr.bin/awk
                % make clean all
                % sudo -E make install
        to enable building kernels again.

20210708:
        Commit 1e0a518d6548 changed the internal KAPI between the NFS
        modules. They all need to be rebuilt from sources.  I did not
        bump __FreeBSD_version, since it was bumped recently.

20210707:
        awk has been updated to the latest one-true-awk version 20210215.
        This contains a number of minor bug fixes.

20210624:
        The NFSv4 client now uses the highest minor version of NFSv4
        supported by the NFSv4 server by default instead of minor version 0,
        for NFSv4 mounts.
        The "minorversion" mount option may be used to override this default.

20210618:
        Bump __FreeBSD_version to 1400024 for LinuxKPI changes.
        Most notably netdev.h can change now as the (last) dependencies
        (mlx4/ofed) are now using struct ifnet directly, but also for PCI
        additions and others.

20210618:
        The directory "blacklisted" under /usr/share/certs/ has been
        renamed to "untrusted".

20210611:
        svnlite has been removed from base. Should you need svn for any reason
        please install the svn package or port.

20210611:
        Commit e1a907a25cfa changed the internal KAPI between the krpc
        and nfsserver.  As such, both modules must be rebuilt from
        sources.  Bump __FreeBSD_version to 1400022.

20210610:
        The an(4) driver has been removed from FreeBSD.

20210608:
        The vendor/openzfs branch was renamed to vendor/openzfs/legacy to
        start tracking OpenZFS upstream more closely. Please see
https://lists.freebsd.org/archives/freebsd-current/2021-June/000153.html
        for details on how to correct any errors that might result. The
        short version is that you need to remove the old branch locally:
            git update-ref -d refs/remotes/freebsd/vendor/openzfs
        (assuming your upstream origin is named 'freebsd').

20210525:
        Commits 17accc08ae15 and de102f870501 add new files to LinuxKPI
        which break drm-kmod.  In addition various other additions where
        committed. Bump __FreeBSD_version to 1400015 to be able to
        detect this.

20210513:
        Commit ca179c4d74f2 changed the package in which the OpenSSL
        libraries and utilities are packaged.
        It is recommended for pkgbase user to do:
        pkg install -f FreeBSD-openssl
        before pkg upgrade otherwise some dependencies might not be met
        and pkg will stop working as libssl will not be present anymore
        on the system.

20210426:
        Commit 875977314881 changed the internal KAPI between
        the nfsd and nfscommon modules.  As such these modules
        need to be rebuilt from sources.
        Without this patch in your NFSv4.1/4.2 server, enabling
        delegations by setting vfs.nfsd.issue_delegations non-zero
        is not recommended.

20210411:
        Commit 7763814fc9c2 changed the internal KAPI between
        the krpc and NFS.  As such, the krpc, nfscommon and
        nfscl modules must all be rebuilt from sources.
        Without this patch, NFSv4.1/4.2 mounts should not
        be done with the nfscbd(8) daemon running, to avoid
        needing a working back channel for server->client RPCs.

20210330:
        Commit 01ae8969a9ee fixed the NFSv4.1/4.2 server so that it
        handles binding of the back channel as required by RFC5661.
        Until this patch is in your server, avoid use of the "nconnects"
        mount option for Linux NFSv4.1/4.2 mounts.

20210225:
        For 64-bit architectures the base system is now built with Position
        Independent Executable (PIE) support enabled by default.  It may be
        disabled using the WITHOUT_PIE knob.  A clean build is required.

20210128:
        Various LinuxKPI functionality was added which conflicts with DRM.
        Please update your drm-kmod port to after the __FreeBSD_version 1400003
        update.

20210121:
        stable/13 branch created.

20210108:
        PC Card attachments for all devices have been removed. In the case of
        wi and cmx, the entire drivers were removed because they were only
        PC Card devices. FreeBSD_version 1300134 should be used for this
        since it was bumped so recently.

20210107:
        Transport-independent parts of HID support have been split off the USB
        code in to separate subsystem.  Kernel configs which include one of
        ums, ukbd, uhid, atp, wsp, wmt, uaudio, ugold or ucycom drivers should
        be updated with adding of "device hid" line.

20210105:
        ncurses installation has been modified to only keep the widechar
        enabled version.  Incremental build is broken for that change, so it
        requires a clean build.

20201223:
        The FreeBSD project has migrated from Subversion to Git. Temporary
        instructions can be found at
        https://github.com/bsdimp/freebsd-git-docs/blob/main/src-cvt.md
        and other documents in that repo.

20201216:
        The services database has been updated to cover more of the basic
        services expected in a modern system. The database is big enough
        that it will cause issues in mergemaster in Releases previous to
        12.2 and 11.3, or in very old current systems from before r358154.

20201215:
        Obsolete in-tree GDB 6.1.1 has been removed.  GDB (including kgdb)
        may be installed from ports or packages.

20201124:
        ping6 has been merged into ping.  It can now be called as "ping -6".
        See ping(8) for details.

20201108:
        Default value of net.add_addr_allfibs has been changed to 0.
        If you have multi-fib configuration and rely on existence of all
        interface routes in every fib, you need to set the above sysctl to 1.

20201030:
        The internal pre-processor in the calendar(1) program has been
        extended to support more C pre-processor commands (e.g. #ifdef, #else,
        and #undef) and to detect unbalanced conditional statements.
        Error messages have been extended to include the filename and line
        number if processing stops to help fixing malformed data files.

20201026:
        All the data files for the calendar(1) program, except calendar.freebsd,
        have been moved to the deskutils/calendar-data port, much like the
        jewish calendar entries were moved to deskutils/hebcal years ago. After
        make delete-old-files, you need to install it to retain full
        functionality. calendar(1) will issue a reminder for files it can't
        find.

20200923:
        LINT files are no longer generated. We now include the relevant NOTES
        files. Note: This may cause conflicts with updating in some cases.
                find sys -name LINT\* -delete
        is suggested across this commit to remove the generated LINT files.

        If you have tried to update with generated files there, the svn
        command you want to un-auger the tree is
                cd sys/amd64/conf
                svn revert -R .
        and then do the above find from the top level. Substitute 'amd64'
        above with where the error message indicates a conflict.

20200824:
        OpenZFS support has been integrated. Do not upgrade root pools until
        the loader is updated to support zstd. Furthermore, we caution against
        'zpool upgrade' for the next few weeks. The change should be transparent
        unless you  want to use new features.

        Not all "NO_CLEAN" build scenarios work across these changes. Many
        scenarios have been tested and fixed, but rebuilding kernels without
        rebuilding world may fail.

        The ZFS cache file has moved from /boot to /etc to match the OpenZFS
        upstream default. A fallback to /boot has been added for mountroot.

        Pool auto import behavior at boot has been moved from the kernel module
        to an explicit "zpool import -a" in one of the rc scripts enabled by
        zfs_enable=YES. This means your non-root zpools won't auto import until
        you upgrade your /etc/rc.d files.

20200824:
        The resume code now notifies devd with the 'kernel' system
        rather than the old 'kern' subsystem to be consistent with
        other use. The old notification will be created as well, but
        will be removed prior to FreeBSD 14.0.

20200821:
        r362275 changed the internal API between the kernel RPC and the
        NFS modules. As such, all the modules must be recompiled from
        sources.

20200817:
        r364330 modified the internal API used between the NFS modules.
        As such, all the NFS modules must be re-compiled from sources.

20200816:
        Clang, llvm, lld, lldb, compiler-rt, libc++, libunwind and openmp have
        been upgraded to 11.0.0.  Please see the 20141231 entry below for
        information about prerequisites and upgrading, if you are not already
        using clang 3.5.0 or higher.

20200810:
        r364092 modified the internal ABI used between the kernel NFS
        modules.  As such, all of these modules need to be rebuilt
        from sources, so a version bump was done.

20200807:
        Makefile.inc has been updated to work around the issue documented in
        20200729. It was a case where the optimization of using symbolic links
        to point to binaries created a situation where we'd run new binaries
        with old libraries starting midway through the installworld process.

20200729:
        r363679 has redefined some undefined behavior in regcomp(3); notably,
        extraneous escapes of most ordinary characters will no longer be
        accepted.  An exp-run has identified all of the problems with this in
        ports, but other non-ports software may need extra escapes removed to
        continue to function.

        Because of this change, installworld may encounter the following error
        from rtld: Undefined symbol "regcomp@FBSD_1.6" -- It is imperative that
        you do not halt installworld. Instead, let it run to completion (whether
        successful or not) and run installworld once more.

20200627:
        A new implementation of bc and dc has been imported in r362681. This
        implementation corrects non-conformant behavior of the previous bc
        and adds GNU bc compatible options. It offers a number of extensions,
        is much faster on large values, and has support for message catalogs
        (a number of languages are already supported, contributions of further
        languages welcome). The option WITHOUT_GH_BC can be used to build the
        world with the previous versions of bc and dc.

20200625:
        r362639 changed the internal API used between the NFS kernel modules.
        As such, they all need to be rebuilt from sources.

20200613:
        r362158 changed the arguments for VFS_CHECKEXP().  As such, any
        out of tree file systems need to be modified and rebuilt.
        Also, any file systems that are modules must be rebuilt.

20200604:
        read(2) of a directory fd is now rejected by default.  root may
        re-enable it for system root only on non-ZFS filesystems with the
        security.bsd.allow_read_dir sysctl(8) MIB if
        security.bsd.suser_enabled=1.

        It may be advised to setup aliases for grep to default to `-d skip` if
        commonly non-recursively grepping a list that includes directories and
        the potential for the resulting stderr output is not tolerable.  Example
        aliases are now installed, commented out, in /root/.cshrc and
        /root/.shrc.

20200523:
        Clang, llvm, lld, lldb, compiler-rt, libc++, libunwind and openmp have
        been upgraded to 10.0.1.  Please see the 20141231 entry below for
        information about prerequisites and upgrading, if you are not already
        using clang 3.5.0 or higher.

20200512:
        Support for obsolete compilers has been removed from the build system.
        Clang 6 and GCC 6.4 are the minimum supported versions.

20200424:
        closefrom(2) has been moved under COMPAT12, and replaced in libc with a
        stub that calls close_range(2).  If using a custom kernel configuration,
        you may want to ensure that the COMPAT_FREEBSD12 option is included, as
        a slightly older -CURRENT userland and older FreeBSD userlands may not
        be functional without closefrom(2).

20200414:
        Upstream DTS from Linux 5.6 was merged and they now have the SID
        and THS (Secure ID controller and THermal Sensor) node present.
        The DTB overlays have now been removed from the tree for the H3/H5 and
        A64 SoCs and the aw_sid and aw_thermal driver have been updated to
        deal with upstream DTS. If you are using those overlays you need to
        remove them from loader.conf and update the DTBs on the FAT partition.

20200310:
        Clang, llvm, lld, lldb, compiler-rt, libc++, libunwind and openmp have
        been upgraded to 10.0.0.  Please see the 20141231 entry below for
        information about prerequisites and upgrading, if you are not already
        using clang 3.5.0 or higher.

20200309:
        The amd(8) automount daemon has been removed from the source tree.
        As of FreeBSD 10.1 autofs(5) is the preferred tool for automounting.
        amd is still available in the sysutils/am-utils port.

20200301:
        Removed brooktree driver (bktr.4) from the tree.

20200229:
        The WITH_GPL_DTC option has been removed.  The BSD-licenced device tree
        compiler in usr.bin/dtc is used on all architectures which use dtc, and
        the GPL dtc is available (if needed) from the sysutils/dtc port.

20200229:
        The WITHOUT_LLVM_LIBUNWIND option has been removed.  LLVM's libunwind
        is used by all supported CPU architectures.

20200229:
        GCC 4.2.1 has been removed from the tree.  The WITH_GCC,
        WITH_GCC_BOOTSTRAP, and WITH_GNUCXX options are no longer available.
        Users who wish to build FreeBSD with GCC must use the external toolchain
        ports or packages.

20200220:
        ncurses has been updated to a newer version (6.2-20200215). Given the ABI
        has changed, users will have to rebuild all the ports that are linked to
        ncurses.

20200217:
        The size of struct vnet and the magic cookie have changed.
        Users need to recompile libkvm and all modules using VIMAGE
        together with their new kernel.

20200212:
        Defining the long deprecated NO_CTF, NO_DEBUG_FILES, NO_INSTALLLIB,
        NO_MAN, NO_PROFILE, and NO_WARNS variables is now an error.  Update
        your Makefiles and scripts to define MK_<var>=no instead as required.

        One exception to this is that program or library Makefiles should
        define MAN to empty rather than setting MK_MAN=no.

20200108:
        Clang/LLVM is now the default compiler and LLD the default
        linker for riscv64.

20200107:
        make universe no longer uses GCC 4.2.1 on any architectures.
        Architectures not supported by in-tree Clang/LLVM require an
        external toolchain package.

20200104:
        GCC 4.2.1 is now not built by default, as part of the GCC 4.2.1
        retirement plan.  Specifically, the GCC, GCC_BOOTSTRAP, and GNUCXX
        options default to off for all supported CPU architectures.  As a
        short-term transition aid they may be enabled via WITH_* options.
        GCC 4.2.1 is expected to be removed from the tree on 2020-03-31.

20200102:
        Support for armv5 has been disconnected and is being removed. The
        machine combination MACHINE=arm MACHINE_ARCH=arm is no longer valid.
        You must now use a MACHINE_ARCH of armv6 or armv7. The default
        MACHINE_ARCH for MACHINE=arm is now armv7.

20191226:
        Clang/LLVM is now the default compiler for all powerpc architectures.
        LLD is now the default linker for powerpc64.  The change for powerpc64
        also includes a change to the ELFv2 ABI, incompatible with the existing
        ABI.

20191226:
        Kernel-loadable random(4) modules are no longer unloadable.

20191222:
        Clang, llvm, lld, lldb, compiler-rt, libc++, libunwind and openmp have
        been upgraded to 9.0.1.  Please see the 20141231 entry below for
        information about prerequisites and upgrading, if you are not already
        using clang 3.5.0 or higher.

20191212:
        r355677 has modified the internal interface used between the
        NFS modules in the kernel. As such, they must all be upgraded
        simultaneously. I will do a version bump for this.

20191205:
        The root certificates of the Mozilla CA Certificate Store have been
        imported into the base system and can be managed with the certctl(8)
        utility.  If you have installed the security/ca_root_nss port or package
        with the ETCSYMLINK option (the default), be advised that there may be
        differences between those included in the port and those included in
        base due to differences in nss branch used as well as general update
        frequency.  Note also that certctl(8) cannot manage certs in the
        format used by the security/ca_root_nss port.

20191120:
        The amd(8) automount daemon has been disabled by default, and will be
        removed in the future.  As of FreeBSD 10.1 the autofs(5) is available
        for automounting.

20191107:
        The nctgpio and wbwd drivers have been moved to the superio bus.
        If you have one of these drivers in a kernel configuration, then
        you should add device superio to it.  If you use one of these drivers
        as a module and you compile a custom set of modules, then you should
        add superio to the set.

20191021:
        KPIs for network drivers to access interface addresses have changed.
        Users need to recompile NIC driver modules together with kernel.

20191021:
        The net.link.tap.user_open sysctl no longer prevents user opening of
        already created /dev/tapNN devices.  Access is still controlled by
        node permissions, just like tun devices.  The net.link.tap.user_open
        sysctl is now used only to allow users to perform devfs cloning of
        tap devices, and the subsequent open may not succeed if the user is not
        in the appropriate group.  This sysctl may be deprecated/removed
        completely in the future.

20191009:
        mips, powerpc, and sparc64 are no longer built as part of
        universe / tinderbox unless MAKE_OBSOLETE_GCC is defined. If
        not defined, mips, powerpc, and sparc64 builds will look for
        the xtoolchain binaries and if installed use them for universe
        builds. As llvm 9.0 becomes vetted for these architectures, they
        will be removed from the list.

20191009:
        Clang, llvm, lld, lldb, compiler-rt, libc++, libunwind and openmp have
        been upgraded to 9.0.0.  Please see the 20141231 entry below for
        information about prerequisites and upgrading, if you are not already
        using clang 3.5.0 or higher.

20191003:
        The hpt27xx, hptmv, hptnr, and hptrr drivers have been removed from
        GENERIC.  They are available as modules and can be loaded by adding
        to /boot/loader.conf hpt27xx_load="YES", hptmv_load="YES",
        hptnr_load="YES", or hptrr_load="YES", respectively.

20190913:
        ntpd no longer by default locks its pages in memory, allowing them
        to be paged out by the kernel. Use rlimit memlock to restore
        historic BSD behaviour. For example, add "rlimit memlock 32"
        to ntp.conf to lock up to 32 MB of ntpd address space in memory.

20190823:
        Several of ping6's options have been renamed for better consistency
        with ping.  If you use any of -ARWXaghmrtwx, you must update your
        scripts.  See ping6(8) for details.

20190727:
        The vfs.fusefs.sync_unmount and vfs.fusefs.init_backgrounded sysctls
        and the "-o sync_unmount" and "-o init_backgrounded" mount options have
        been removed from mount_fusefs(8).  You can safely remove them from
        your scripts, because they had no effect.

        The vfs.fusefs.fix_broken_io, vfs.fusefs.sync_resize,
        vfs.fusefs.refresh_size, vfs.fusefs.mmap_enable,
        vfs.fusefs.reclaim_revoked, and vfs.fusefs.data_cache_invalidate
        sysctls have been removed.  If you felt the need to set any of them to
        a non-default value, please tell asomers@FreeBSD.org why.

20190713:
        Default permissions on the /var/account/acct file (and copies of it
        rotated by periodic daily scripts) are changed from 0644 to 0640
        because the file contains sensitive information that should not be
        world-readable.  If the /var/account directory must be created by
        rc.d/accounting, the mode used is now 0750.  Admins who use the
        accounting feature are encouraged to change the mode of an existing
        /var/account directory to 0750 or 0700.

20190620:
        Entropy collection and the /dev/random device are no longer optional
        components.  The "device random" option has been removed.
        Implementations of distilling algorithms can still be made loadable
        with "options RANDOM_LOADABLE" (e.g., random_fortuna.ko).

20190612:
        Clang, llvm, lld, lldb, compiler-rt, libc++, libunwind and openmp have
        been upgraded to 8.0.1.  Please see the 20141231 entry below for
        information about prerequisites and upgrading, if you are not already
        using clang 3.5.0 or higher.

20190608:
        A fix was applied to i386 kernel modules to avoid panics with
        dpcpu or vnet.  Users need to recompile i386 kernel modules
        having pcpu or vnet sections or they will refuse to load.

20190513:
        User-wired pages now have their own counter,
        vm.stats.vm.v_user_wire_count.  The vm.max_wired sysctl was renamed
        to vm.max_user_wired and changed from an unsigned int to an unsigned
        long.  bhyve VMs wired with the -S are now subject to the user
        wiring limit; the vm.max_user_wired sysctl may need to be tuned to
        avoid running into the limit.

20190507:
        The IPSEC option has been removed from GENERIC.  Users requiring
        ipsec(4) must now load the ipsec(4) kernel module.

20190507:
        The tap(4) driver has been folded into tun(4), and the module has been
        renamed to tuntap.  You should update any kld_list="if_tap" or
        kld_list="if_tun" entries in /etc/rc.conf, if_tap_load="YES" or
        if_tun_load="YES" entries in /boot/loader.conf to load the if_tuntap
        module instead, and "device tap" or "device tun" entries in kernel
        config files to select the tuntap device instead.

20190418:
        The following knobs have been added related to tradeoffs between
        safe use of the random device and availability in the absence of
        entropy:

        kern.random.initial_seeding.bypass_before_seeding: tunable; set
        non-zero to bypass the random device prior to seeding, or zero to
        block random requests until the random device is initially seeded.
        For now, set to 1 (unsafe) by default to restore pre-r346250 boot
        availability properties.

        kern.random.initial_seeding.read_random_bypassed_before_seeding:
        read-only diagnostic sysctl that is set when bypass is enabled and
        read_random(9) is bypassed, to enable programmatic handling of this
        initial condition, if desired.

        kern.random.initial_seeding.arc4random_bypassed_before_seeding:
        Similar to the above, but for arc4random(9) initial seeding.

        kern.random.initial_seeding.disable_bypass_warnings: tunable; set
        non-zero to disable warnings in dmesg when the same conditions are
        met as for the diagnostic sysctls above.  Defaults to zero, i.e.,
        produce warnings in dmesg when the conditions are met.

20190416:
        The loadable random module KPI has changed; the random_infra_init()
        routine now requires a 3rd function pointer for a bool (*)(void)
        method that returns true if the random device is seeded (and
        therefore unblocked).

20190404:
        r345895 reverts r320698. This implies that an nfsuserd(8) daemon
        built from head sources between r320757 (July 6, 2017) and
        r338192 (Aug. 22, 2018) will not work unless the "-use-udpsock"
        is added to the command line.
        nfsuserd daemons built from head sources that are post-r338192 are
        not affected and should continue to work.

20190320:
        The fuse(4) module has been renamed to fusefs(4) for consistency with
        other filesystems.  You should update any kld_load="fuse" entries in
        /etc/rc.conf, fuse_load="YES" entries in /boot/loader.conf, and
        "options FUSE" entries in kernel config files.

20190304:
        Clang, llvm, lld, lldb, compiler-rt and libc++ have been upgraded to
        8.0.0.  Please see the 20141231 entry below for information about
        prerequisites and upgrading, if you are not already using clang 3.5.0
        or higher.

20190226:
        geom_uzip(4) depends on the new module xz.  If geom_uzip is statically
        compiled into your custom kernel, add 'device xz' statement to the
        kernel config.

20190219:
        drm and drm2 have been removed from the tree. Please see
        https://wiki.freebsd.org/Graphics for the latest information on
        migrating to the drm ports.

20190131:
        Iflib is no longer unconditionally compiled into the kernel.  Drivers
        using iflib and statically compiled into the kernel, now require
        the 'device iflib' config option.  For the same drivers loaded as
        modules on kernels not having 'device iflib', the iflib.ko module
        is loaded automatically.

20190125:
        The IEEE80211_AMPDU_AGE and AH_SUPPORT_AR5416 kernel configuration
        options no longer exist since r343219 and r343427 respectively;
        nothing uses them, so they should be just removed from custom
        kernel config files.

20181230:
        r342635 changes the way efibootmgr(8) works by requiring users to add
        the -b (bootnum) parameter for commands where the bootnum was previously
        specified with each option. For example 'efibootmgr -B 0001' is now
        'efibootmgr -B -b 0001'.

20181220:
        r342286 modifies the NFSv4 server so that it obeys vfs.nfsd.nfs_privport
        in the same as it is applied to NFSv2 and 3.  This implies that NFSv4
        servers that have vfs.nfsd.nfs_privport set will only allow mounts
        from clients using a reserved port. Since both the FreeBSD and Linux
        NFSv4 clients use reserved ports by default, this should not affect
        most NFSv4 mounts.

20181219:
        The XLP config has been removed. We can't support 64-bit atomics in this
        kernel because it is running in 32-bit mode. XLP users must transition
        to running a 64-bit kernel (XLP64 or XLPN32).

        The mips GXEMUL support has been removed from FreeBSD. MALTA* + qemu is
        the preferred emulator today and we don't need two different ones.

        The old sibyte / swarm / Broadcom BCM1250 support has been
        removed from the mips port.

20181211:
        Clang, llvm, lld, lldb, compiler-rt and libc++ have been upgraded to
        7.0.1.  Please see the 20141231 entry below for information about
        prerequisites and upgrading, if you are not already using clang 3.5.0
        or higher.

20181211:
        Remove the timed and netdate programs from the base tree.  Setting
        the time with these daemons has been obsolete for over a decade.

20181126:
        On amd64, arm64 and armv7 (architectures that install LLVM's ld.lld
        linker as /usr/bin/ld) GNU ld is no longer installed as ld.bfd, as
        it produces broken binaries when ifuncs are in use.  Users needing
        GNU ld should install the binutils port or package.

20181123:
        The BSD crtbegin and crtend code has been enabled by default. It has
        had extensive testing on amd64, arm64, and i386. It can be disabled
        by building a world with -DWITHOUT_BSD_CRTBEGIN.

20181115:
        The set of CTM commands (ctm, ctm_smail, ctm_rmail, ctm_dequeue)
        has been converted to a port (misc/ctm) and will be removed from
        FreeBSD-13.  It is available as a package (ctm) for all supported
        FreeBSD versions.

20181110:
        The default newsyslog.conf(5) file has been changed to only include
        files in /etc/newsyslog.conf.d/ and /usr/local/etc/newsyslog.conf.d/ if
        the filenames end in '.conf' and do not begin with a '.'.

        You should check the configuration files in these two directories match
        this naming convention. You can verify which configuration files are
        being included using the command:
                $ newsyslog -Nrv

20181019:
        Stable/12 was branched created.

20181015:
        Ports for the DRM modules have been simplified. Now, amd64 users should
        just install the drm-kmod port. All others should install
        drm-legacy-kmod.

        Graphics hardware that's newer than about 2010 usually works with
        drm-kmod.  For hardware older than 2013, however, some users will need
        to use drm-legacy-kmod if drm-kmod doesn't work for them. Hardware older
        than 2008 usually only works in drm-legacy-kmod. The graphics team can
        only commit to hardware made since 2013 due to the complexity of the
        market and difficulty to test all the older cards effectively. If you
        have hardware supported by drm-kmod, you are strongly encouraged to use
        that as you will get better support.

        Other than KPI chasing, drm-legacy-kmod will not be updated. As outlined
        elsewhere, the drm and drm2 modules will be eliminated from the src base
        soon (with a limited exception for arm). Please update to the package
        asap and report any issues to x11@freebsd.org.

        Generally, anybody using the drm*-kmod packages should add
        WITHOUT_DRM_MODULE=t and WITHOUT_DRM2_MODULE=t to avoid nasty
        cross-threading surprises, especially with automatic driver
        loading from X11 startup. These will become the defaults in 13-current
        shortly.

20181012:
        The ixlv(4) driver has been renamed to iavf(4).  As a consequence,
        custom kernel and module loading configuration files must be updated
        accordingly.  Moreover, interfaces previous presented as ixlvN to the
        system are now exposed as iavfN and network configuration files must
        be adjusted as necessary.

20181009:
        OpenSSL has been updated to version 1.1.1.  This update included
        additional various API changes throughout the base system.  It is
        important to rebuild third-party software after upgrading.  The value
        of __FreeBSD_version has been bumped accordingly.

20181006:
        The legacy DRM modules and drivers have now been added to the loader's
        module blacklist, in favor of loading them with kld_list in rc.conf(5).
        The module blacklist may be overridden with the loader.conf(5)
        'module_blacklist' variable, but loading them via rc.conf(5) is strongly
        encouraged.

20181002:
        The cam(4) based nda(4) driver will be used over nvd(4) by default on
        powerpc64. You may set 'options NVME_USE_NVD=1' in your kernel conf or
        loader tunable 'hw.nvme.use_nvd=1' if you wish to use the existing
        driver.  Make sure to edit /boot/etc/kboot.conf and fstab to use the
        nda device name.

20180913:
        Reproducible build mode is now on by default, in preparation for
        FreeBSD 12.0.  This eliminates build metadata such as the user,
        host, and time from the kernel (and uname), unless the working tree
        corresponds to a modified checkout from a version control system.
        The previous behavior can be obtained by setting the /etc/src.conf
        knob WITHOUT_REPRODUCIBLE_BUILD.

20180826:
        The Yarrow CSPRNG has been removed from the kernel as it has not been
        supported by its designers since at least 2003. Fortuna has been the
        default since FreeBSD-11.

20180822:
        devctl freeze/thaw have gone into the tree, the rc scripts have been
        updated to use them and devmatch has been changed.  You should update
        kernel, userland and rc scripts all at the same time.

20180818:
        The default interpreter has been switched from 4th to Lua.
        LOADER_DEFAULT_INTERP, documented in build(7), will override the default
        interpreter.  If you have custom FORTH code you will need to set
        LOADER_DEFAULT_INTERP=4th (valid values are 4th, lua or simp) in
        src.conf for the build.  This will create default hard links between
        loader and loader_4th instead of loader and loader_lua, the new default.
        If you are using UEFI it will create the proper hard link to loader.efi.

        bhyve uses userboot.so. It remains 4th-only until some issues are solved
        regarding coexisting with multiple versions of FreeBSD are resolved.

20180815:
        ls(1) now respects the COLORTERM environment variable used in other
        systems and software to indicate that a colored terminal is both
        supported and desired.  If ls(1) is suddenly emitting colors, they may
        be disabled again by either removing the unwanted COLORTERM from your
        environment, or using `ls --color=never`.  The ls(1) specific CLICOLOR
        may not be observed in a future release.

20180808:
        The default pager for most commands has been changed to "less".  To
        restore the old behavior, set PAGER="more" and MANPAGER="more -s" in
        your environment.

20180731:
        The jedec_ts(4) driver has been removed. A superset of its functionality
        is available in the jedec_dimm(4) driver, and the manpage for that
        driver includes migration instructions. If you have "device jedec_ts"
        in your kernel configuration file, it must be removed.

20180730:
        amd64/GENERIC now has EFI runtime services, EFIRT, enabled by default.
        This should have no effect if the kernel is booted via BIOS/legacy boot.
        EFIRT may be disabled via a loader tunable, efi.rt.disabled, if a system
        has a buggy firmware that prevents a successful boot due to use of
        runtime services.

20180727:
        Atmel AT91RM9200 and AT91SAM9, Cavium CNS 11xx and XScale
        support has been removed from the tree. These ports were
        obsolete and/or known to be broken for many years.

20180723:
        loader.efi has been augmented to participate more fully in the
        UEFI boot manager protocol. loader.efi will now look at the
        BootXXXX environment variable to determine if a specific kernel
        or root partition was specified. XXXX is derived from BootCurrent.
        efibootmgr(8) manages these standard UEFI variables.

20180720:
        zfsloader's functionality has now been folded into loader.
        zfsloader is no longer necessary once you've updated your
        boot blocks. For a transition period, we will install a
        hardlink for zfsloader to loader to allow a smooth transition
        until the boot blocks can be updated (hard link because old
        zfs boot blocks don't understand symlinks).

20180719:
        ARM64 now have efifb support, if you want to have serial console
        on your arm64 board when an screen is connected and the bootloader
        setup a frame buffer for us to use, just add :
        boot_serial=YES
        boot_multicons=YES
        in /boot/loader.conf
        For Raspberry Pi 3 (RPI) users, this is needed even if you don't have
        an screen connected as the firmware will setup a frame buffer are that
        u-boot will expose as an EFI frame buffer.

20180719:
        New uid:gid added, ntpd:ntpd (123:123).  Be sure to run mergemaster
        or take steps to update /etc/passwd before doing installworld on
        existing systems.  Do not skip the "mergemaster -Fp" step before
        installworld, as described in the update procedures near the bottom
        of this document.  Also, rc.d/ntpd now starts ntpd(8) as user ntpd
        if the new mac_ntpd(4) policy is available, unless ntpd_flags or
        the ntp config file contain options that change file/dir locations.
        When such options (e.g., "statsdir" or "crypto") are used, ntpd can
        still be run as non-root by setting ntpd_user=ntpd in rc.conf, after
        taking steps to ensure that all required files/dirs are accessible
        by the ntpd user.

20180717:
        Big endian arm support has been removed.

20180711:
        The static environment setup in kernel configs is no longer mutually
        exclusive with the loader(8) environment by default.  In order to
        restore the previous default behavior of disabling the loader(8)
        environment if a static environment is present, you must specify
        loader_env.disabled=1 in the static environment.

20180705:
        The ABI of syscalls used by management tools like sockstat and
        netstat has been broken to allow 32-bit binaries to work on
        64-bit kernels without modification.  These programs will need
        to match the kernel in order to function.  External programs may
        require minor modifications to accommodate a change of type in
        structures from pointers to 64-bit virtual addresses.

20180702:
        On i386 and amd64 atomics are now inlined. Out of tree modules using
        atomics will need to be rebuilt.

20180701:
        The '%I' format in the kern.corefile sysctl limits the number of
        core files that a process can generate to the number stored in the
        debug.ncores sysctl. The '%I' format is replaced by the single digit
        index. Previously, if all indexes were taken the kernel would overwrite
        only a core file with the highest index in a filename.
        Currently the system will create a new core file if there is a free
        index or if all slots are taken it will overwrite the oldest one.

20180630:
        Clang, llvm, lld, lldb, compiler-rt and libc++ have been upgraded to
        6.0.1.  Please see the 20141231 entry below for information about
        prerequisites and upgrading, if you are not already using clang 3.5.0
        or higher.

20180628:
        r335753 introduced a new quoting method. However, etc/devd/devmatch.conf
        needed to be changed to work with it. This change was made with r335763
        and requires a mergemaster / etcupdate / etc to update the installed
        file.

20180612:
        r334930 changed the interface between the NFS modules, so they all
        need to be rebuilt.  r335018 did a __FreeBSD_version bump for this.

20180530:
        As of r334391 lld is the default amd64 system linker; it is installed
        as /usr/bin/ld.  Kernel build workarounds (see 20180510 entry) are no
        longer necessary.

20180530:
        The kernel / userland interface for devinfo changed, so you'll
        need a new kernel and userland as a pair for it to work (rebuilding
        lib/libdevinfo is all that's required). devinfo and devmatch will
        not work, but everything else will when there's a mismatch.

20180523:
        The on-disk format for hwpmc callchain records has changed to include
        threadid corresponding to a given record. This changes the field offsets
        and thus requires that libpmcstat be rebuilt before using a kernel
        later than r334108.

20180517:
        The vxge(4) driver has been removed.  This driver was introduced into
        HEAD one week before the Exar left the Ethernet market and is not
        known to be used.  If you have device vxge in your kernel config file
        it must be removed.

20180510:
        The amd64 kernel now requires a ld that supports ifunc to produce a
        working kernel, either lld or a newer binutils. lld is built by default
        on amd64, and the 'buildkernel' target uses it automatically. However,
        it is not the default linker, so building the kernel the traditional
        way requires LD=ld.lld on the command line (or LD=/usr/local/bin/ld for
        binutils port/package). lld will soon be default, and this requirement
        will go away.

        NOTE: As of r334391 lld is the default system linker on amd64, and no
        workaround is necessary.

20180508:
        The nxge(4) driver has been removed.  This driver was for PCI-X 10g
        cards made by s2io/Neterion.  The company was acquired by Exar and
        no longer sells or supports Ethernet products.  If you have device
        nxge in your kernel config file it must be removed.

20180504:
        The tz database (tzdb) has been updated to 2018e.  This version more
        correctly models time stamps in time zones with negative DST such as
        Europe/Dublin (from 1971 on), Europe/Prague (1946/7), and
        Africa/Windhoek (1994/2017).  This does not affect the UT offsets, only
        time zone abbreviations and the tm_isdst flag.

20180502:
        The ixgb(4) driver has been removed.  This driver was for an early and
        uncommon legacy PCI 10GbE for a single ASIC, Intel 82597EX. Intel
        quickly shifted to the long lived ixgbe family.  If you have device
        ixgb in your kernel config file it must be removed.

20180501:
        The lmc(4) driver has been removed.  This was a WAN interface
        card that was already reportedly rare in 2003, and had an ambiguous
        license.  If you have device lmc in your kernel config file it must
        be removed.

20180413:
        Support for Arcnet networks has been removed.  If you have device
        arcnet or device cm in your kernel config file they must be
        removed.

20180411:
        Support for FDDI networks has been removed.  If you have device
        fddi or device fpa in your kernel config file they must be
        removed.

20180406:
        In addition to supporting RFC 3164 formatted messages, the
        syslogd(8) service is now capable of parsing RFC 5424 formatted
        log messages. The main benefit of using RFC 5424 is that clients
        may now send log messages with timestamps containing year numbers,
        microseconds and time zone offsets.

        Similarly, the syslog(3) C library function has been altered to
        send RFC 5424 formatted messages to the local system logging
        daemon. On systems using syslogd(8), this change should have no
        negative impact, as long as syslogd(8) and the C library are
        updated at the same time. On systems using a different system
        logging daemon, it may be necessary to make configuration
        adjustments, depending on the software used.

        When using syslog-ng, add the 'syslog-protocol' flag to local
        input sources to enable parsing of RFC 5424 formatted messages:

                source src {
                        unix-dgram("/var/run/log" flags(syslog-protocol));
                }

        When using rsyslog, disable the 'SysSock.UseSpecialParser' option
        of the 'imuxsock' module to let messages be processed by the
        regular RFC 3164/5424 parsing pipeline:

                module(load="imuxsock" SysSock.UseSpecialParser="off")

        Do note that these changes only affect communication between local
        applications and syslogd(8). The format that syslogd(8) uses to
        store messages on disk or forward messages to other systems
        remains unchanged. syslogd(8) still uses RFC 3164 for these
        purposes. Options to customize this behaviour will be added in the
        future. Utilities that process log files stored in /var/log are
        thus expected to continue to function as before.

        __FreeBSD_version has been incremented to 1200061 to denote this
        change.

20180328:
        Support for token ring networks has been removed. If you
        have "device token" in your kernel config you should remove
        it. No device drivers supported token ring.

20180323:
        makefs was modified to be able to tag ISO9660 El Torito boot catalog
        entries as EFI instead of overloading the i386 tag as done previously.
        The amd64 mkisoimages.sh script used to build amd64 ISO images for
        release was updated to use this. This may mean that makefs must be
        updated before "make cdrom" can be run in the release directory. This
        should be as simple as:

                $ cd $SRCDIR/usr.sbin/makefs
                $ make depend all install

20180212:
        FreeBSD boot loader enhanced with Lua scripting. It's purely opt-in for
        now by building WITH_LOADER_LUA and WITHOUT_FORTH in /etc/src.conf.
        Co-existence for the transition period will come shortly. Booting is a
        complex environment and test coverage for Lua-enabled loaders has been
        thin, so it would be prudent to assume it might not work and make
        provisions for backup boot methods.

20180211:
        devmatch functionality has been turned on in devd. It will automatically
        load drivers for unattached devices. This may cause unexpected drivers
        to be loaded. Please report any problems to current@ and
        imp@freebsd.org.

20180114:
        Clang, llvm, lld, lldb, compiler-rt and libc++ have been upgraded to
        6.0.0.  Please see the 20141231 entry below for information about
        prerequisites and upgrading, if you are not already using clang 3.5.0
        or higher.

20180110:
        LLVM's lld linker is now used as the FreeBSD/amd64 bootstrap linker.
        This means it is used to link the kernel and userland libraries and
        executables, but is not yet installed as /usr/bin/ld by default.

        To revert to ld.bfd as the bootstrap linker, in /etc/src.conf set
        WITHOUT_LLD_BOOTSTRAP=yes

20180110:
        On i386, pmtimer has been removed. Its functionality has been folded
        into apm. It was a no-op on ACPI in current for a while now (but was
        still needed on i386 in FreeBSD 11 and earlier). Users may need to
        remove it from kernel config files.

20180104:
        The use of RSS hash from the network card aka flowid has been
        disabled by default for lagg(4) as it's currently incompatible with
        the lacp and loadbalance protocols.

        This can be re-enabled by setting the following in loader.conf:
        net.link.lagg.default_use_flowid="1"

20180102:
        The SW_WATCHDOG option is no longer necessary to enable the
        hardclock-based software watchdog if no hardware watchdog is
        configured. As before, SW_WATCHDOG will cause the software
        watchdog to be enabled even if a hardware watchdog is configured.

20171215:
        r326887 fixes the issue described in the 20171214 UPDATING entry.
        r326888 flips the switch back to building GELI support always.

20171214:
        r362593 broke ZFS + GELI support for reasons unknown. However,
        it also broke ZFS support generally, so GELI has been turned off
        by default as the lesser evil in r326857. If you boot off ZFS and/or
        GELI, it might not be a good time to update.

20171125:
        PowerPC users must update loader(8) by rebuilding world before
        installing a new kernel, as the protocol connecting them has
        changed. Without the update, loader metadata will not be passed
        successfully to the kernel and users will have to enter their
        root partition at the kernel mountroot prompt to continue booting.
        Newer versions of loader can boot old kernels without issue.

20171110:
        The LOADER_FIREWIRE_SUPPORT build variable has been renamed to
        WITH/OUT_LOADER_FIREWIRE. LOADER_{NO_,}GELI_SUPPORT has been renamed
        to WITH/OUT_LOADER_GELI.

20171106:
        The naive and non-compliant support of posix_fallocate(2) in ZFS
        has been removed as of r325320.  The system call now returns EINVAL
        when used on a ZFS file.  Although the new behavior complies with the
        standard, some consumers are not prepared to cope with it.
        One known victim is lld prior to r325420.

20171102:
        Building in a FreeBSD src checkout will automatically create object
        directories now rather than store files in the current directory if
        'make obj' was not ran.  Calling 'make obj' is no longer necessary.
        This feature can be disabled by setting WITHOUT_AUTO_OBJ=yes in
        /etc/src-env.conf (not /etc/src.conf), or passing the option in the
        environment.

20171101:
        The default MAKEOBJDIR has changed from /usr/obj/<srcdir> for native
        builds, and /usr/obj/<arch>/<srcdir> for cross-builds, to a unified
        /usr/obj/<srcdir>/<arch>.  This behavior can be changed to the old
        format by setting WITHOUT_UNIFIED_OBJDIR=yes in /etc/src-env.conf,
        the environment, or with -DWITHOUT_UNIFIED_OBJDIR when building.
        The UNIFIED_OBJDIR option is a transitional feature that will be
        removed for 12.0 release; please migrate to the new format for any
        tools by looking up the OBJDIR used by 'make -V .OBJDIR' means rather
        than hardcoding paths.

20171028:
        The native-xtools target no longer installs the files by default to the
        OBJDIR.  Use the native-xtools-install target with a DESTDIR to install
        to ${DESTDIR}/${NXTP} where NXTP defaults to /nxb-bin.

20171021:
        As part of the boot loader infrastructure cleanup, LOADER_*_SUPPORT
        options are changing from controlling the build if defined / undefined
        to controlling the build with explicit 'yes' or 'no' values. They will
        shift to WITH/WITHOUT options to match other options in the system.

20171010:
        libstand has turned into a private library for sys/boot use only.
        It is no longer supported as a public interface outside of sys/boot.

20171005:
        The arm port has split armv6 into armv6 and armv7. armv7 is now
        a valid TARGET_ARCH/MACHINE_ARCH setting. If you have an armv7 system
        and are running a kernel from before r324363, you will need to add
        MACHINE_ARCH=armv7 to 'make buildworld' to do a native build.

20171003:
        When building multiple kernels using KERNCONF, non-existent KERNCONF
        files will produce an error and buildkernel will fail. Previously
        missing KERNCONF files silently failed giving no indication as to
        why, only to subsequently discover during installkernel that the
        desired kernel was never built in the first place.

20170912:
        The default serial number format for CTL LUNs has changed.  This will
        affect users who use /dev/diskid/* device nodes, or whose FibreChannel
        or iSCSI clients care about their LUNs' serial numbers.  Users who
        require serial number stability should hardcode serial numbers in
        /etc/ctl.conf .

20170912:
        For 32-bit arm compiled for hard-float support, soft-floating point
        binaries now always get their shared libraries from
        LD_SOFT_LIBRARY_PATH (in the past, this was only used if
        /usr/libsoft also existed). Only users with a hard-float ld.so, but
        soft-float everything else should be affected.

20170826:
        The geli password typed at boot is now hidden.  To restore the previous
        behavior, see geli(8) for configuration options.

20170825:
        Move PMTUD blackhole counters to TCPSTATS and remove them from bare
        sysctl values.  Minor nit, but requires a rebuild of both world/kernel
        to complete.

20170814:
        "make check" behavior (made in ^/head@r295380) has been changed to
        execute from a limited sandbox, as opposed to executing from
        ${TESTSDIR}.

        Behavioral changes:
        - The "beforecheck" and "aftercheck" targets are now specified.
        - ${CHECKDIR} (added in commit noted above) has been removed.
        - Legacy behavior can be enabled by setting
          WITHOUT_MAKE_CHECK_USE_SANDBOX in src.conf(5) or the environment.

        If the limited sandbox mode is enabled, "make check" will execute
        "make distribution", then install, execute the tests, and clean up the
        sandbox if successful.

        The "make distribution" and "make install" targets are typically run as
        root to set appropriate permissions and ownership at installation time.
        The end-user should set "WITH_INSTALL_AS_USER" in src.conf(5) or the
        environment if executing "make check" with limited sandbox mode using
        an unprivileged user.

20170808:
        Since the switch to GPT disk labels, fsck for UFS/FFS has been
        unable to automatically find alternate superblocks. As of r322297,
        the information needed to find alternate superblocks has been
        moved to the end of the area reserved for the boot block.
        Filesystems created with a newfs of this vintage or later
        will create the recovery information. If you have a filesystem
        created prior to this change and wish to have a recovery block
        created for your filesystem, you can do so by running fsck in
        foreground mode (i.e., do not use the -p or -y options). As it
        starts, fsck will ask ``SAVE DATA TO FIND ALTERNATE SUPERBLOCKS''
        to which you should answer yes.

20170728:
        As of r321665, an NFSv4 server configuration that services
        Kerberos mounts or clients that do not support the uid/gid in
        owner/owner_group string capability, must explicitly enable
        the nfsuserd daemon by adding nfsuserd_enable="YES" to the
        machine's /etc/rc.conf file.

20170722:
        Clang, llvm, lldb, compiler-rt and libc++ have been upgraded to 5.0.0.
        Please see the 20141231 entry below for information about prerequisites
        and upgrading, if you are not already using clang 3.5.0 or higher.

20170701:
        WITHOUT_RCMDS is now the default. Set WITH_RCMDS if you need the
        r-commands (rlogin, rsh, etc.) to be built with the base system.

20170625:
        The FreeBSD/powerpc platform now uses a 64-bit type for time_t.  This is
        a very major ABI incompatible change, so users of FreeBSD/powerpc must
        be careful when performing source upgrades.  It is best to run
        'make installworld' from an alternate root system, either a live
        CD/memory stick, or a temporary root partition.  Additionally, all ports
        must be recompiled.  powerpc64 is largely unaffected, except in the case
        of 32-bit compatibility.  All 32-bit binaries will be affected.

20170623:
        Forward compatibility for the "ino64" project have been committed. This
        will allow most new binaries to run on older kernels in a limited
        fashion.  This prevents many of the common foot-shooting actions in the
        upgrade as well as the limited ability to roll back the kernel across
        the ino64 upgrade. Complicated use cases may not work properly, though
        enough simpler ones work to allow recovery in most situations.

20170620:
        Switch back to the BSDL dtc (Device Tree Compiler). Set WITH_GPL_DTC
        if you require the GPL compiler.

20170619:
        Forward compatibility for the "ino64" project have been committed. This
        will allow most new binaries to run on older kernels in a limited
        fashion.  This prevents many of the common foot-shooting actions in the
        upgrade as well as the limited ability to roll back the kernel across
        the ino64 upgrade. Complicated use cases may not work properly, though
        enough simpler ones work to allow recovery in most situations.

20170618:
        The internal ABI used for communication between the NFS kernel modules
        was changed by r320085, so __FreeBSD_version was bumped to
        ensure all the NFS related modules are updated together.

20170617:
        The ABI of struct event was changed by extending the data
        member to 64bit and adding ext fields.  For upgrade, same
        precautions as for the entry 20170523 "ino64" must be
        followed.

20170531:
        The GNU roff toolchain has been removed from base. To render manpages
        which are not supported by mandoc(1), man(1) can fallback on GNU roff
        from ports (and recommends to install it).
        To render roff(7) documents, consider using GNU roff from ports or the
        heirloom doctools roff toolchain from ports via pkg install groff or
        via pkg install heirloom-doctools.

20170524:
        The ath(4) and ath_hal(4) modules now build piecemeal to allow for
        smaller runtime footprint builds.  This is useful for embedded systems
        which only require one chipset support.

        If you load it as a module, make sure this is in /boot/loader.conf:

        if_ath_load="YES"

        This will load the HAL, all chip/RF backends and if_ath_pci.
        If you have if_ath_pci in /boot/loader.conf, ensure it is after
        if_ath or it will not load any HAL chipset support.

        If you want to selectively load things (eg on cheaper ARM/MIPS
        platforms where RAM is at a premium) you should:

        * load ath_hal
        * load the chip modules in question
        * load ath_rate, ath_dfs
        * load ath_main
        * load if_ath_pci and/or if_ath_ahb depending upon your particular
          bus bind type - this is where probe/attach is done.

        For further comments/feedback, poke adrian@ .

20170523:
        The "ino64" 64-bit inode project has been committed, which extends
        a number of types to 64 bits.  Upgrading in place requires care and
        adherence to the documented upgrade procedure.

        If using a custom kernel configuration ensure that the
        COMPAT_FREEBSD11 option is included (as during the upgrade the
        system will be running the ino64 kernel with the existing world).

        For the safest in-place upgrade begin by removing previous build
        artifacts via "rm -rf /usr/obj/*".  Then, carefully follow the full
        procedure documented below under the heading "To rebuild everything and
        install it on the current system."  Specifically, a reboot is required
        after installing the new kernel before installing world. While an
        installworld normally works by accident from multiuser after rebooting
        the proper kernel, there are many cases where this will fail across this
        upgrade and installworld from single user is required.

20170424:
        The NATM framework including the en(4), fatm(4), hatm(4), and
        patm(4) devices has been removed.  Consumers should plan a
        migration before the end-of-life date for FreeBSD 11.

20170420:
        GNU diff has been replaced by a BSD licensed diff. Some features of GNU
        diff has not been implemented, if those are needed a newer version of
        GNU diff is available via the diffutils package under the gdiff name.

20170413:
        As of r316810 for ipfilter, keep frags is no longer assumed when
        keep state is specified in a rule. r316810 aligns ipfilter with
        documentation in man pages separating keep frags from keep state.
        This allows keep state to be specified without forcing keep frags
        and allows keep frags to be specified independently of keep state.
        To maintain previous behaviour, also specify keep frags with
        keep state (as documented in ipf.conf.5).

20170407:
        arm64 builds now use the base system LLD 4.0.0 linker by default,
        instead of requiring that the aarch64-binutils port or package be
        installed. To continue using aarch64-binutils, set
        CROSS_BINUTILS_PREFIX=/usr/local/aarch64-freebsd/bin .

20170405:
        The UDP optimization in entry 20160818 that added the sysctl
        net.inet.udp.require_l2_bcast has been reverted.  L2 broadcast
        packets will no longer be treated as L3 broadcast packets.

20170331:
        Binds and sends to the loopback addresses, IPv6 and IPv4, will now
        use any explicitly assigned loopback address available in the jail
        instead of using the first assigned address of the jail.

20170329:
        The ctl.ko module no longer implements the iSCSI target frontend:
        cfiscsi.ko does instead.

        If building cfiscsi.ko as a kernel module, the module can be loaded
        via one of the following methods:
        - `cfiscsi_load="YES"` in loader.conf(5).
        - Add `cfiscsi` to `$kld_list` in rc.conf(5).
        - ctladm(8)/ctld(8), when compiled with iSCSI support
          (`WITH_ISCSI=yes` in src.conf(5))

        Please see cfiscsi(4) for more details.

20170316:
        The mmcsd.ko module now additionally depends on geom_flashmap.ko.
        Also, mmc.ko and mmcsd.ko need to be a matching pair built from the
        same source (previously, the dependency of mmcsd.ko on mmc.ko was
        missing, but mmcsd.ko now will refuse to load if it is incompatible
        with mmc.ko).

20170315:
        The syntax of ipfw(8) named states was changed to avoid ambiguity.
        If you have used named states in the firewall rules, you need to modify
        them after installworld and before rebooting. Now named states must
        be prefixed with colon.

20170311:
        The old drm (sys/dev/drm/) drivers for i915 and radeon have been
        removed as the userland we provide cannot use them. The KMS version
        (sys/dev/drm2) supports the same hardware.

20170302:
        Clang, llvm, lldb, compiler-rt and libc++ have been upgraded to 4.0.0.
        Please see the 20141231 entry below for information about prerequisites
        and upgrading, if you are not already using clang 3.5.0 or higher.

20170221:
        The code that provides support for ZFS .zfs/ directory functionality
        has been reimplemented.  It's not possible now to create a snapshot
        by mkdir under .zfs/snapshot/.  That should be the only user visible
        change.

20170216:
        EISA bus support has been removed. The WITH_EISA option is no longer
        valid.

20170215:
        MCA bus support has been removed.

20170127:
        The WITH_LLD_AS_LD / WITHOUT_LLD_AS_LD build knobs have been renamed
        WITH_LLD_IS_LD / WITHOUT_LLD_IS_LD, for consistency with CLANG_IS_CC.

20170112:
        The EM_MULTIQUEUE kernel configuration option is deprecated now that
        the em(4) driver conforms to iflib specifications.

20170109:
        The igb(4), em(4) and lem(4) ethernet drivers are now implemented via
        IFLIB.  If you have a custom kernel configuration that excludes em(4)
        but you use igb(4), you need to re-add em(4) to your custom
        configuration.

20161217:
        Clang, llvm, lldb, compiler-rt and libc++ have been upgraded to 3.9.1.
        Please see the 20141231 entry below for information about prerequisites
        and upgrading, if you are not already using clang 3.5.0 or higher.

20161124:
        Clang, llvm, lldb, compiler-rt and libc++ have been upgraded to 3.9.0.
        Please see the 20141231 entry below for information about prerequisites
        and upgrading, if you are not already using clang 3.5.0 or higher.

20161119:
        The layout of the pmap structure has changed for powerpc to put the pmap
        statistics at the front for all CPU variations.  libkvm(3) and all tools
        that link against it need to be recompiled.

20161030:
        isl(4) and cyapa(4) drivers now require a new driver,
        chromebook_platform(4), to work properly on Chromebook-class hardware.
        On other types of hardware the drivers may need to be configured using
        device hints.  Please see the corresponding manual pages for details.

20161017:
        The urtwn(4) driver was merged into rtwn(4) and now consists of
        rtwn(4) main module + rtwn_usb(4) and rtwn_pci(4) bus-specific
        parts.
        Also, firmware for RTL8188CE was renamed due to possible name
        conflict (rtwnrtl8192cU(B) -> rtwnrtl8192cE(B))

20161015:
        GNU rcs has been removed from base.  It is available as packages:
        - rcs: Latest GPLv3 GNU rcs version.
        - rcs57: Copy of the latest version of GNU rcs (GPLv2) before it was
        removed from base.

20161008:
        Use of the cc_cdg, cc_chd, cc_hd, or cc_vegas congestion control
        modules now requires that the kernel configuration contain the
        TCP_HHOOK option. (This option is included in the GENERIC kernel.)

20161003:
        The WITHOUT_ELFCOPY_AS_OBJCOPY src.conf(5) knob has been retired.
        ELF Tool Chain's elfcopy is always installed as /usr/bin/objcopy.

20160924:
        Relocatable object files with the extension of .So have been renamed
        to use an extension of .pico instead.  The purpose of this change is
        to avoid a name clash with shared libraries on case-insensitive file
        systems.  On those file systems, foo.So is the same file as foo.so.

20160918:
        GNU rcs has been turned off by default.  It can (temporarily) be built
        again by adding WITH_RCS knob in src.conf.
        Otherwise, GNU rcs is available from packages:
        - rcs: Latest GPLv3 GNU rcs version.
        - rcs57: Copy of the latest version of GNU rcs (GPLv2) from base.

20160918:
        The backup_uses_rcs functionality has been removed from rc.subr.

20160908:
        The queue(3) debugging macro, QUEUE_MACRO_DEBUG, has been split into
        two separate components, QUEUE_MACRO_DEBUG_TRACE and
        QUEUE_MACRO_DEBUG_TRASH.  Define both for the original
        QUEUE_MACRO_DEBUG behavior.

20160824:
        r304787 changed some ioctl interfaces between the iSCSI userspace
        programs and the kernel.  ctladm, ctld, iscsictl, and iscsid must be
        rebuilt to work with new kernels.  __FreeBSD_version has been bumped
        to 1200005.

20160818:
        The UDP receive code has been updated to only treat incoming UDP
        packets that were addressed to an L2 broadcast address as L3
        broadcast packets.  It is not expected that this will affect any
        standards-conforming UDP application.  The new behaviour can be
        disabled by setting the sysctl net.inet.udp.require_l2_bcast to
        0.

20160818:
        Remove the openbsd_poll system call.
        __FreeBSD_version has been bumped because of this.

20160708:
        The stable/11 branch has been created from head@r302406.

After branch N is created, entries older than the N-2 branch point are removed
from this file. After stable/14 is branched and current becomes FreeBSD 15,
entries older than stable/12 branch point will be removed from current's
UPDATING file.

COMMON ITEMS:

        General Notes
        -------------
        Sometimes, obscure build problems are the result of environment
        poisoning.  This can happen because the make utility reads its
        environment when searching for values for global variables.  To run
        your build attempts in an "environmental clean room", prefix all make
        commands with 'env -i '.  See the env(1) manual page for more details.
        Occasionally a build failure will occur with "make -j" due to a race
        condition.  If this happens try building again without -j, and please
        report a bug if it happens consistently.

        When upgrading from one major version to another it is generally best to
        upgrade to the latest code in the currently installed branch first, then
        do an upgrade to the new branch. This is the best-tested upgrade path,
        and has the highest probability of being successful.  Please try this
        approach if you encounter problems with a major version upgrade.  Since
        the stable 4.x branch point, one has generally been able to upgrade from
        anywhere in the most recent stable branch to head / current (or even the
        last couple of stable branches). See the top of this file when there's
        an exception.

        The update process will emit an error on an attempt to perform a build
        or install from a FreeBSD version below the earliest supported version.
        When updating from an older version the update should be performed one
        major release at a time, including running `make delete-old` at each
        step.

        When upgrading a live system, having a root shell around before
        installing anything can help undo problems. Not having a root shell
        around can lead to problems if pam has changed too much from your
        starting point to allow continued authentication after the upgrade.

        This file should be read as a log of events. When a later event changes
        information of a prior event, the prior event should not be deleted.
        Instead, a pointer to the entry with the new information should be
        placed in the old entry. Readers of this file should also sanity check
        older entries before relying on them blindly. Authors of new entries
        should write them with this in mind.

        ZFS notes
        ---------
        When upgrading the boot ZFS pool to a new version (via zpool upgrade),
        always follow these three steps:

        1) recompile and reinstall the ZFS boot loader and boot block
        (this is part of "make buildworld" and "make installworld")

        2) update the ZFS boot block on your boot drive (only required when
        doing a zpool upgrade):

        When booting on x86 via BIOS, use the following to update the ZFS boot
        block on the freebsd-boot partition of a GPT partitioned drive ada0:
                gpart bootcode -p /boot/gptzfsboot -i $N ada0
        The value $N will typically be 1.  For EFI booting, see EFI notes.

        3) zpool upgrade the root pool. New bootblocks will work with old
        pools, but not vice versa, so they need to be updated before any
        zpool upgrade.

        Non-boot pools do not need these updates.

        EFI notes
        ---------

        There are two locations the boot loader can be installed into. The
        current location (and the default) is \efi\freebsd\loader.efi and using
        efibootmgr(8) to configure it. The old location, that must be used on
        deficient systems that don't honor efibootmgr(8) protocols, is the
        fallback location of \EFI\BOOT\BOOTxxx.EFI. Generally, you will copy
        /boot/loader.efi to this location, but on systems installed a long time
        ago the ESP may be too small and /boot/boot1.efi may be needed unless
        the ESP has been expanded in the meantime.

        Recent systems will have the ESP mounted on /boot/efi, but older ones
        may not have it mounted at all, or mounted in a different
        location. Older arm SD images with MBR used /boot/msdos as the
        mountpoint. The ESP is a MSDOS filesystem.

        The EFI boot loader rarely needs to be updated. For ZFS booting,
        however, you must update loader.efi before you do 'zpool upgrade' the
        root zpool, otherwise the old loader.efi may reject the upgraded zpool
        since it does not automatically understand some new features.

        See loader.efi(8) and uefi(8) for more details.

        To build a kernel
        -----------------
        If you are updating from a prior version of FreeBSD (even one just
        a few days old), you should follow this procedure.  It is the most
        failsafe as it uses a /usr/obj tree with a fresh mini-buildworld,

        make kernel-toolchain
        make -DALWAYS_CHECK_MAKE buildkernel KERNCONF=YOUR_KERNEL_HERE
        make -DALWAYS_CHECK_MAKE installkernel KERNCONF=YOUR_KERNEL_HERE

        To test a kernel once
        ---------------------
        If you just want to boot a kernel once (because you are not sure
        if it works, or if you want to boot a known bad kernel to provide
        debugging information) run
        make installkernel KERNCONF=YOUR_KERNEL_HERE KODIR=/boot/testkernel
        nextboot -k testkernel

        To rebuild everything and install it on the current system.
        -----------------------------------------------------------
        # Note: sometimes if you are running current you gotta do more than
        # is listed here if you are upgrading from a really old current.

        <make sure you have good level 0 dumps>
        make buildworld
        make buildkernel KERNCONF=YOUR_KERNEL_HERE
        make installkernel KERNCONF=YOUR_KERNEL_HERE
                                                        [1]
        <reboot in single user>                         [3]
        etcupdate -p                                    [5]
        make installworld
        etcupdate -B                                    [4]
        make delete-old                                 [6]
        <reboot>

        To cross-install current onto a separate partition
        --------------------------------------------------
        # In this approach we use a separate partition to hold
        # current's root, 'usr', and 'var' directories.   A partition
        # holding "/", "/usr" and "/var" should be about 2GB in
        # size.

        <make sure you have good level 0 dumps>
        <boot into -stable>
        make buildworld
        make buildkernel KERNCONF=YOUR_KERNEL_HERE
        <maybe newfs current's root partition>
        <mount current's root partition on directory ${CURRENT_ROOT}>
        make installworld DESTDIR=${CURRENT_ROOT} -DDB_FROM_SRC
        make distribution DESTDIR=${CURRENT_ROOT} # if newfs'd
        make installkernel KERNCONF=YOUR_KERNEL_HERE DESTDIR=${CURRENT_ROOT}
        cp /etc/fstab ${CURRENT_ROOT}/etc/fstab                    # if newfs'd
        <edit ${CURRENT_ROOT}/etc/fstab to mount "/" from the correct partition>
        <reboot into current>
        <do a "native" rebuild/install as described in the previous section>
        <maybe install compatibility libraries from ports/misc/compat*>
        <reboot>


        To upgrade in-place from stable to current
        ----------------------------------------------
        <make sure you have good level 0 dumps>
        make buildworld                                 [9]
        make buildkernel KERNCONF=YOUR_KERNEL_HERE      [8]
        make installkernel KERNCONF=YOUR_KERNEL_HERE
                                                        [1]
        <reboot in single user>                         [3]
        etcupdate -p                                    [5]
        make installworld
        etcupdate -B                                    [4]
        make delete-old                                 [6]
        <reboot>

        Make sure that you've read the UPDATING file to understand the
        tweaks to various things you need.  At this point in the life
        cycle of current, things change often and you are on your own
        to cope.  The defaults can also change, so please read ALL of
        the UPDATING entries.

        Also, if you are tracking -current, you must be subscribed to
        freebsd-current@freebsd.org.  Make sure that before you update
        your sources that you have read and understood all the recent
        messages there.  If in doubt, please track -stable which has
        much fewer pitfalls.

        [1] If you have third party modules, such as vmware, you should disable
        them at this point so they don't crash your system on
        reboot. Alternatively, you should rebuild all the modules you have in
        your system and install them as well.  If you are running -current, you
        should seriously consider placing all sources to all the modules for
        your system (or symlinks to them) in /usr/local/sys/modules so this
        happens automatically. If all your modules come from ports, then adding
        the port origin directories to PORTS_MODULES instead is also automatic
        and effective, eg:
             PORTS_MODULES+=x11/nvidia-driver

        [3] From the bootblocks, boot -s, and then do
                fsck -p
                mount -u /
                mount -a
                sh /etc/rc.d/zfs start  # mount zfs filesystem, if needed
                cd src                  # full path to source
                adjkerntz -i            # if CMOS is wall time
        Also, when doing a major release upgrade, it is required that you boot
        into single user mode to do the installworld.

        [4] Note: This step is non-optional.  Failure to do this step
        can result in a significant reduction in the functionality of the
        system.  Attempting to do it by hand is not recommended and those
        that pursue this avenue should read this file carefully, as well
        as the archives of freebsd-current and freebsd-hackers mailing lists
        for potential gotchas.  See etcupdate(8) for more information.

        [5] Usually this step is a no-op.  However, from time to time
        you may need to do this if you get unknown user in the following
        step.

        [6] This only deletes old files and directories. Old libraries
        can be deleted by "make delete-old-libs", but you have to make
        sure that no program is using those libraries anymore.

        [8] The new kernel must be able to run existing binaries used by an
        installworld.  When upgrading across major versions, the new kernel's
        configuration must include the correct COMPAT_FREEBSD<n> option for
        existing binaries (e.g. COMPAT_FREEBSD11 to run 11.x binaries).  Failure
        to do so may leave you with a system that is hard to boot to recover. A
        GENERIC kernel will include suitable compatibility options to run
        binaries from older branches.  Note that the ability to run binaries
        from unsupported branches is not guaranteed.

        Make sure that you merge any new devices from GENERIC since the
        last time you updated your kernel config file. Options also
        change over time, so you may need to adjust your custom kernels
        for these as well.

        [9] If CPUTYPE is defined in your /etc/make.conf, make sure to use the
        "?=" instead of the "=" assignment operator, so that buildworld can
        override the CPUTYPE if it needs to.

        MAKEOBJDIRPREFIX must be defined in an environment variable, and
        not on the command line, or in /etc/make.conf.  buildworld will
        warn if it is improperly defined.
FORMAT:

This file contains a list, in reverse chronological order, of major
breakages in tracking -current.  It is not guaranteed to be a complete
list of such breakages, and only contains entries since September 23, 2011.
If you need to see UPDATING entries from before that date, you will need
to fetch an UPDATING file from an older FreeBSD release.

Copyright information:

Copyright 1998-2009 M. Warner Losh <imp@FreeBSD.org>

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