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<!ENTITY % release PUBLIC "-//FreeBSD//ENTITIES Release Specification//EN" "release.ent">
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<!ENTITY security SYSTEM "../../share/xml/security.xml">
<!ENTITY errata SYSTEM "../../share/xml/errata.xml">
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<article xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0">
  <info><title>&os; &release.current; Release Notes</title>
    
  <author><orgname>The &os; Project</orgname></author>

  <pubdate>$FreeBSD$</pubdate>

  <copyright>
    <year>2015</year>
    <holder role="mailto:doc@FreeBSD.org">The &os; Documentation Project</holder>
  </copyright>

  <legalnotice xml:id="trademarks" role="trademarks">
    &tm-attrib.freebsd;
    &tm-attrib.ibm;
    &tm-attrib.ieee;
    &tm-attrib.intel;
    &tm-attrib.sparc;
    &tm-attrib.general;
  </legalnotice>

  <abstract>
    <para>The release notes for &os; &release.current; contain a summary
      of the changes made to the &os; base system on the
      &release.branch; development line.
      This document lists applicable security advisories that were issued since
      the last release, as well as significant changes to the &os;
      kernel and userland.
      Some brief remarks on upgrading are also presented.</para>
  </abstract>
  </info>

<sect1 xml:id="intro">
  <title>Introduction</title>

  <para>This document contains the release notes for &os;
    &release.current;.  It
    describes recently added, changed, or deleted features of &os;.
    It also provides some notes on upgrading
    from previous versions of &os;.</para>

  <para releasetype="current">The &release.type; distribution to which these release notes
    apply represents the latest point along the &release.branch; development
    branch since &release.branch; was created.  Information regarding pre-built, binary
    &release.type; distributions along this branch
    can be found at <uri xlink:href="&release.url;"></uri>.</para>

  <para releasetype="snapshot">The &release.type; distribution to which these release notes
    apply represents a point along the &release.branch; development
    branch between &release.prev; and the future &release.next;.
    Information regarding
    pre-built, binary &release.type; distributions along this branch
    can be found at <uri xlink:href="&release.url;"></uri>.</para>

  <para releasetype="release">This distribution of &os; &release.current; is a
    &release.type; distribution.  It can be found at <uri xlink:href="&release.url;" />
    or any of its mirrors.       More
    information on obtaining this (or other) &release.type;
    distributions of &os; can be found in the <link xlink:href="&url.books.handbook;/mirrors.html"><quote>Obtaining
    &os;</quote> appendix</link> to the <link xlink:href="&url.books.handbook;/">&os;
    Handbook</link>.</para>

  <para>All users are encouraged to consult the release errata before
    installing &os;.  The errata document is updated with
    <quote>late-breaking</quote> information discovered late in the
    release cycle or after the release.  Typically, it contains
    information on known bugs, security advisories, and corrections to
    documentation.  An up-to-date copy of the errata for &os;
    &release.current; can be found on the &os; Web site.</para>

</sect1>

  <sect1 xml:id="new">
    <title>What's New</title>

    <para>This section describes the most user-visible new or changed
      features in &os; since &release.prev;.</para>

    <para>Typical release note items document recent security
      advisories issued after &release.prev;, new drivers or hardware
      support, new commands or options, major bug fixes, or
      contributed software upgrades.  They may also list changes to
      major ports/packages or release engineering practices.  Clearly
      the release notes cannot list every single change made to &os;
      between releases; this document focuses primarily on security
      advisories, user-visible changes, and major architectural
      improvements.</para>

    <sect2 xml:id="security">
      <title>Security Advisories</title>

      <para>Problems described in the following security advisories have
        been fixed.  For more information, consult the individual
        advisories available from
        <uri xlink:href="http://security.FreeBSD.org/">http://security.FreeBSD.org/</uri>.</para>

      &security;
    </sect2>

    <sect2 xml:id="errata">
      <title>Errata Notices</title>

      &errata;
    </sect2>

    <sect2 xml:id="kernel">
      <title>Kernel Changes</title>

      <para arch="ia64" revision="209326">The maximum number of pages
        used for DMA bounce buffer pool has been increased from 256 to
        1024.</para>

      <para arch="powerpc" revision="209765">The default value of
        <varname>kern.hz</varname> has been increased from 100 to
        1000.</para>

      <para arch="powerpc" revision="209767">The SMP kernel now works on
        MPC7400-based Apple desktop machines such as
        PowerMac3,3.</para>

      <para arch="powerpc" revision="211593">&os;/powerpc now supports
        DMA bounce buffer which is required on systems with larger RAM
        than 4GB.</para>

      <para arch="mips" revision="215938">&os;/mips support has been
        improved.  It now supports SMP on a SWARM with a dual-core
        Sibyte processor.</para>

      <para arch="mips">&os;/mips now supports Netlogic Microsystems'
        XLR and XLS multi-core processor families.</para>

      <para arch="sparc64" revision="215598">&os;/sparc64 now supports
        reservation-based physical memory allocation which provides
        better performance.</para>

      <para arch="amd64" revision="214620">&os;/amd64 now always sets
        the KVA space as equal to or larger than physical memory size.
        The default size was calculated based on one-third of the
        physical memory size by a code derived from one for i386.  It
        has been changed because constraints for memory space are not
        severe on amd64 and this change would help to prevent a
        <quote>kmem_map too small</quote> panic which often occurs
        when using ZFS.</para>

      <para arch="amd64,i386" revision="214621">CPU topology detection
        for Intel CPUs has been improved.</para>

      <para arch="amd64,i386" revision="215513">ACPI suspend/resume
        functionality support has been improved.</para>

      <para arch="amd64,i386" revision="215513">&os; kernel now
        supports <function>kern_fpu_enter()</function> and
        <function>kern_fpu_leave()</function> KPIs which allow the
        kernel subsystems to use XMM register files used in Intel SSE
        (Streaming SIMD Extensions).</para>

      <para arch="amd64,i386,ia64" revision="215006">The &man.acpi.4;
        driver now uses ACPI Reset Register capability by default only
        when a flag in the FADT which indicates it is available.  This
        behavior was controlled by a &man.sysctl.8; variable
        <varname>hw.acpi.handle_reboot</varname> and the default value
        was always set to <literal>0</literal>.</para>

      <para arch="amd64,i386,ia64" revision="215521">The &man.acpi.4;
        driver now supports new loader tunables
        <varname>hw.acpi.install_interface</varname> and
        <varname>hw.acpi.remove_interface</varname>.  For more
        details, see &man.acpi.4; manual page.</para>

      <para revision="209788">The &man.alq.9; support has been
        improved.  The <function>alq_writen()</function> and
        <function>alq_getn()</function> KPIs have been extended to
        support variable length messages, which is enabled at ALQ
        creation time depending on the arguments passed to
        <function>alq_open()</function>.  Also, the
        <literal>ALQ_NOACTIVATE</literal> and
        <literal>ALQ_ORDERED</literal> flags have been added to allow
        ALQ consumers to have more control over I/O scheduling and
        resource acquisition respectively.  These extensions are fully
        backward compatible.</para>

      <para revision="209783">The &man.alq.9; support is now provided
        as a kernel module <filename>alq.ko</filename>.</para>

      <para revision="209692">The &man.ddb.8; kernel debugger now
        supports an optional delay in <command>reset</command> and
        <command>reboot</command> commands.  This allows an
        administrator to break the system into debugger and trigger
        automatic textdump when an unattended panic occurs.</para>

      <para revision="212230">The &man.ddb.8; kernel debugger now
        supports a <command>show cdev</command> command.  This
        displays the list of all created cdev's, consisting of devfs
        node name and struct cdev address.</para>

      <para revision="214326">The &os; <filename>GENERIC</filename>
        kernel is now compiled with <option>KDB</option> and
        <option>KDB_TRACE</option> options.  From 8.2-RELEASE the
        kernel supports displaying a stack trace on panic by using
        &man.stack.9; facility with no debugger backend like
        &man.ddb.8;.  Note that this does not change the default
        behaviors of the <filename>GENERIC</filename> kernel on
        panic.</para>

      <para revision="213554,213556,213560">The following
        &man.sysctl.8; variables are also now loader tunables:
        <varname>vm.kmem_size</varname>,
        <varname>vm.kmem_size_max</varname>, and
        <varname>vm.kmem_size_min</varname>,
        <varname>debug.kdb.stop_cpus</varname>,
        <varname>debug.trace_on_panic</varname>, and
        <varname>kern.sync_on_panic</varname>.  Also, new
        &man.sysctl.8; variables <varname>vm.kmem_map_size</varname>
        for the current kmem map size and
        <varname>vm.kmem_map_free</varname> for largest contiguous
        free range in kmem map, <varname>vfs.ncsizefactor</varname>
        for size factor for namecache, and
        <varname>vfs.ncnegfactor</varname> for ratio of negative
        namecache entries have been added.</para>

      <para revision="212427">The &os; &man.memguard.9; framework has
        been improved to make it able to detect use-after-free of
        allocated memories over a longer time.  For more details, see
        &man.memguard.9; manual page.</para>

      <para revision="214756"><literal>PT_LWPINFO</literal> request to
        obtain information about the kernel thread that caused the
        traced process to stop in the &man.ptrace.2; process tracing
        and debugging facility has been improved.  It now reports
        system call entry and leave events, as well as availability of
        <varname>siginfo_t</varname> accompanying the reported
        signal.</para>

      <para revision="214254">The &os; &man.crypto.4; framework
        (opencrypto) now supports XTS-AES (XEX-TCB-CTS, or XEX-based
        Tweaked Code Book mode with CipherText Stealing), which is
        defined in IEEE Std. 1619-2007.</para>

      <para arch="amd64" revision="215788">Xen HVM support in
        &os;/amd64 kernel has been improved.  For more details, see
        &man.xen.4; manual page.</para>

      <para arch="amd64,i386" revision="214784">The qpi(4) pseudo bus
        driver has been added.  This supports extra PCI buses on Intel
        QPI chipsets where various hardware such as memory controllers
        for each socket is connected.</para>

      <sect3 xml:id="boot">
        <title>Boot Loader Changes</title>

        <para revision="213994">&os; now fully supports GPT (GUID
          Partition Table).  Checksums of primary header and primary
          partition table are verified properly now.</para>

        <para arch="powerpc" revision="215919,215920">Memory
          management issues that prevented &os; OpenFirmware loader
          and netbooting from working have been fixed.</para>

        <para revision="212717">The &man.pxeboot.8; now uses NFS
          version 3 instead of version 2 by default.</para>
      </sect3>

      <sect3 xml:id="proc">
        <title>Hardware Support</title>

        <para arch="amd64,i386" revision="215633">The &man.aesni.4;
          driver has been added.  This supports AES accelerator on
          Intel CPUs and accelerates AES operations for
          &man.crypto.4;.</para>

        <para arch="amd64,i386" revision="210476">The &man.aibs.4;
          driver has been added.  This supports the hardware sensors
          in ASUS motherboards and replaces the &man.acpi.aiboost.4;
          driver.</para>

        <para arch="amd64,i386" revision="211914">The &man.coretemp.4;
          driver now supports Xeon 5500/5600 series.</para>

        <para arch="powerpc" revision="215694">&os;/powerpc now
          supports the I2C bus in Apple System Management Unit.</para>

        <para arch="powerpc" revision="215695">A device driver that
          supports CPU temperature sensors on PowerMac 11,2 has been
          added.</para>

        <para revision="215482">The &man.ehci.4;, &man.ohci.4;, and
          &man.uhci.4; driver now support LOW speed BULK transfer
          mode.</para>

        <para arch="amd64,i386" revision="209952">The &man.ichwd.4;
          driver now supports Intel NM10 Express chipset watchdog
          timer.</para>

        <para revision="215036">The &man.tpm.4; driver, which supports
          Trusted Platform Module has been added.</para>

        <para revision="215944">The xhci(4) driver, which supports
          Extensible Host Controller Interface (xHCI) and USB 3.0, has
          been added.</para>

        <sect4 xml:id="mm">
          <title>Multimedia Support</title>

          <para>The &os; Linux emulation subsystem now supports the
            <application>video4linux</application> API.  This requires
            native <application>video4linux</application> hardware
            drivers such as the ones provided by <filename
            role="ports">multimedia/pwcbsd</filename> and <filename
            role="ports">multimedia/webcamd</filename>.</para>

          <para revision="215483">MIDI input buffer size in the
            &man.uaudio.4; driver has been changed.  This fixes a
            problem where the input appears several seconds
            late.</para>

          <para revision="215484">An issue in the &man.uaudio.4;
            driver that prevented some USB audio devices from working
            has been fixed.</para>
        </sect4>

        <sect4 xml:id="net-if">
          <title>Network Interface Support</title>

          <para revision="212021">The &man.alc.4; driver now supports
            Atheros AR8151/AR8152 PCIe Gigabit/Fast Ethernet
            controllers.</para>

          <para revision="215003">A bug in the &man.alc.4; driver was
            fixed that could lead to a system freeze when the system
            was booted without a cable plugged in.  This symptom was
            found in AR8132 on EEE PC.</para>

          <para revision="212011">The TX interrupt moderation timer in
            the &man.alc.4; driver has been reduced from 50ms to 1ms.
            The 50ms timer resulted in a poor UDP performance.</para>

          <para revision="214297,214298,214301">The &man.axe.4; driver
            has been improved for stability and better performance on
            the TX packet rate.</para>

          <para revision="214997">The &man.bge.4; driver now supports
            BCM5718 x2 PCI Express dual-port gigabit Ethernet
            controller family.  This family is the successor to the
            BCM5714/BCM5715 family and supports IPv4/IPv6 checksum
            offloading, TSO, VLAN hardware tagging, jumbo frames,
            MSI/MSIX, IOV, RSS and TSS.  The current version of the
            driver supports all hardware features except IOV and
            RSS/TSS.</para>

          <para revision="211367">A bug in the &man.bge.4; driver which
            prevented TSO from working in BCM57780 has been
            fixed.</para>

          <para revision="214700">A bug in the &man.bge.4; driver that
            could wrongly disable the TX checksum offloading feature
            as well when one tries to disable only the RX checksum
            offloading has been fixed.</para>

          <para revision="214714">Some improvements for reliability of
            the &man.bge.4; driver with BCM5906 controller has been
            made.</para>

          <para revision="214698">The &man.bge.4; driver now supports
            hardware MAC statistics in controller's internal memory
            for BCM5705 or newer Broadcom controllers.  These counters
            can be accessed via &man.sysctl.8; variable
            <varname>dev.bge.<replaceable>N</replaceable>.stats.*</varname>
            and provide useful information to diagnose driver
            issues.</para>

          <para revision="213109">UDP checksum offloading in the
            &man.bge.4; driver has been disabled by default.  This is
            because Broadcom controllers have a bug which can generate
            UDP datagrams with checksum value <literal>0</literal>
            when TX UDP checksum offloading is enabled.  The checksum
            offloading can be enabled by using the following loader
            tunable:</para>

          <programlisting>dev.bge.<replaceable>N</replaceable>.forced_udpcsum</programlisting>

          <para revision="213593">A bug in the &man.bge.4; driver that
            could lead to poor performance on a system with more than
            4 GB RAM has been fixed.  The cause was that all of
            Broadcom controllers except the BCM5755 and later have a
            bug in 4 GB-boundary DMA processing and used the bounce
            buffer in an inefficient way.</para>

          <para revision="212275">The &man.bwi.4; driver, which supports
            Broadcom BCM430* and BCM431* family Wireless Ethernet
            controllers, has been added.  This is not compiled into
            the <filename>GENERIC</filename> kernel because there are
            some problems.  The kernel module
            <filename>if_bwi.ko</filename> is available and can be
            loaded without recompiling the kernel to enable this
            driver.</para>

          <para revision="212274">A bug in the &man.bwn.4; driver that
            prevented WPA authentication from working has been
            fixed.</para>

          <para revision="215499">A bug in the &man.cdce.4; driver has
            been fixed.</para>

          <para revision="211848">The &man.cxgb.4; driver now supports
            the following new &man.sysctl.8; variables:
            <varname>hw.cxgb.nfilters</varname> sets the maximum
            number of entries in the hardware filter table,
            <varname>dev.cxgbc.<replaceable>N</replaceable>.pkt_timestamp</varname>
            provides packet timestamp instead of connection hash, and
            <varname>dev.cxgbc.<replaceable>N</replaceable>.core_clock</varname>
            provides the core clock frequency in kHz.</para>

          <para>The &man.em.4; driver has been updated to version
            7.1.9.</para>

          <para>The &man.igb.4; driver has been updated to version
            2.0.7.</para>

          <para revision="209309">The &man.em.4; and &man.igb.4; drivers
            now provide statistics counters as &man.sysctl.8; MIB
            objects.</para>

          <para revision="211241">The &man.em.4; and &man.igb.4; drivers
            now support the &man.led.4; interface via
            <filename>/dev/led/em<replaceable>N</replaceable></filename>
            and
            <filename>/dev/led/igb<replaceable>N</replaceable></filename>
            for identification LED control.  The following command
            line makes the LED blink on <literal>em0</literal>:</para>

          <screen>&prompt.root; echo f2 &gt; /dev/led/em0</screen>

          <para revision="212150">The &man.epair.4; virtual Ethernet
            interface driver now supports explicit UP/DOWN linkstate.
            This fixes an issue when it is used with the &man.carp.4;
            protocol.</para>

          <para revision="214717">The &man.fxp.4; driver now supports
            TSO over VLAN on i82550 and i82551 controllers.</para>

          <para revision="210673">The &man.iwn.4; driver now supports
            Intel Wireless WiFi Link 6000 series.  The firmware has
            been updated to version 9.221.4.1.</para>

          <para revision="212386">The &man.ixgbe.4;
            driver is now also provided as a kernel module.</para>

          <para revision="209308,215970,217593">The &man.ixgbe.4;
            driver has been updated to version 2.3.8.  It now supports
            82599, better interrupt handling, hardware assist to LRO,
            VM SRIOV interface, and so on.</para>

          <para
            revision="211379,215881,215890,2105894,216002,216023,216029,216031,216033">The
            &man.miibus.4; has been rewritten for the generic IEEE
            802.3 annex 31B full duplex flow control support.  The
            &man.alc.4;, &man.bge.4;, &man.bce.4;, &man.cas.4;,
            &man.fxp.4;, &man.gem.4;, &man.jme.4;, &man.msk.4;,
            &man.nfe.4;, &man.re.4;, &man.stge.4;, and &man.xl.4;
            drivers along with atphy(4), bmtphy(4), brgphy(4),
            e1000phy(4), gentbi(4), inphy(4), ip1000phy(4), jmphy(4),
            nsgphy(4), nsphyter(4), and &man.rgephy.4; have been
            updated to support flow control via this facility.</para>

          <para revision="212386">The &man.mwlfw.4;
            driver is now also provided as a kernel module.</para>

          <para revision="216054">A bug in the &man.mxge.4; driver
            that prevented TSO from working has been fixed.</para>

          <para revision="215456">The &man.nfe.4; driver now supports
            WoL (Wake on LAN).</para>

          <para revision="215218">The &man.re.4; driver now supports
            64-bit DMA addressing for RTL810xE/RTL8168/RTL8111 PCIe
            controllers.</para>

          <para revision="215405">The &man.re.4; driver now supports
            hardware interrupt moderation of TX completion interrupts
            on RTL8169/RTL8168 controllers.</para>

          <para revision="211377">The &man.rl.4; driver now supports WoL
            (Wake on LAN) on RTL8139B or newer controllers.</para>

          <para revision="215222">The &man.rl.4; driver now supports
            reading hardware statistics counters by setting a
            &man.sysctl.8; variable
            <varname>dev.rl.<replaceable>N</replaceable>.stats</varname>
            to <literal>1</literal>.</para>

          <para revision="212039">The &man.rl.4; driver now supports a
            device hint to change a way of register access.  Although
            some newer RTL8139 controllers support memory-mapped
            register access, it is difficult to detect the support
            automatically.  For this reason the driver uses I/O
            mapping by default and provides the following device hint.
            If it is set to <literal>0</literal>, the driver uses
            memory mapping for register access.</para>

          <programlisting>hint.rl.<replaceable>N</replaceable>.prefer_iomap="0"</programlisting>

          <para>Note that the default value is <literal>1</literal>.</para>

          <para revision="214407">The &man.rl.4; driver has improved
            interrupt handling.  It now has better TX performance
            under high RX load.</para>

          <para revision="215216">A bug in the &man.sk.4; driver has
            been fixed.  It did not program the station address for
            Yukon controllers and overriding the station address with
            &man.ifconfig.8; was not possible.</para>

          <para revision="211359">The &man.sk.4; driver now disables TX
            checksum offloading by default.  This is because some
            revisions of the Yukon controller generate corrupted frames.
            The checksum offloading can be enabled manually by using
            <option>txcsum</option> option in the &man.ifconfig.8;
            utility.</para>

          <para revision="212468,213612,213628">The &man.sis.4; driver
            now works on all supported platforms.  Some stability and
            performance issues have also been fixed.</para>

          <para revision="213637">The &man.sis.4; driver now supports
            WoL (Wake on LAN) on NS DP8315 controller.</para>

          <para revision="213626">A tunable
            <varname>dev.sis.<replaceable>N</replaceable>.manual_pad</varname>
            for the &man.sis.4; driver has been added.  This controls
            whether padding with 0x00 for short frames is done by CPU,
            rather than the controller.  The reason why this tunable
            has been added is that NS DP83815/DP83816 pads them with
            0xff though RFC 1042 specifies it should be 0x00.  The
            tunable is disabled by default, which means padding with
            0xff is used because padding with 0x00 by software needs
            extra CPU cycles.  Enabling <varname>manual_pad</varname>,
            by setting this &man.sysctl.8; variable to a non-zero
            value, forces the use of software padding.</para>

          <para revision="211357">The &man.ste.4; driver now supports
            a device hint to change the device register access mode.
            The driver uses memory-mapped register access by default,
            but this caused stability problems with some old IC Plus
            Corp (formerly Sundace) controllers.  The following device
            hint makes the driver use I/O mapping for register
            access:</para>

          <programlisting>hint.ste.<replaceable>N</replaceable>.prefer_iomap="1"</programlisting>

          <para revision="213120">The &man.xl.4; driver now supports
            WoL (Wake on LAN).  Note that not all controllers support
            this functionality and some need an additional remote
            wakeup cable.</para>
        </sect4>
      </sect3>

      <sect3 xml:id="net-proto">
        <title>Network Protocols</title>

        <para revision="213505">An issue in the &man.carp.4; pseudo
          interface and linkstate changes of the underlying interfaces
          has been fixed.  This happened when a &man.carp.4; interface
          was created before the underlying interface and its
          linkstate became <literal>UP</literal>.</para>

    <para>The stdtime part of libc, &man.zdump.8; and &man.zic.8;
      have been updated from the <application>tzcode2004a</application>
      release to the <application>tzcode2009h</application> release.
      If you have upgraded from source or via the &man.freebsd-update.8;,
      then please run &man.tzsetup.8; to install a new /etc/localtime.
      </para>

        <para revision="215342">A new loader tunable
          <varname>net.link.ifqmaxlen</varname> has been added.  It
          specifies the default value of send interface queue length.
          The default value for this parameter is
          <varname>50</varname>.</para>

        <para revision="212742">The <literal>ngtee</literal> action in
          the &man.ipfw.4; packet filter subsystem has been changed.
          It no longer accepts a packet.</para>

        <para revision="214108">A possible panic in the &man.ipfw.4;
          pseudo interface for logging has been fixed.</para>

        <para revision="209691">IPsec flow distribution has been
          improved for more parallel processing.</para>

        <para revision="209277">A bug in the &os; IPv4 stack that
          prevented adding a proxy ARP entry over &man.netgraph.4;
          interfaces has been fixed.</para>

        <para revision="211435">A bug in the &os; IPv6 stack that
          prevented an <option>-I</option> in the &man.ping6.8;
          utility from working with
          <varname>net.inet6.ip6.use_defaultzone=1</varname> has been
          fixed.</para>

        <para revision="214111">The &man.lagg.4; interface now
          supports a &man.sysctl.8; variable
          <varname>net.link.lagg.failover_rx_all</varname>.  This
          controls whether to accept input packets on any link in a
          failover lagg.</para>

        <para revision="215869">The &man.ng.eiface.4; &man.netgraph.4;
          node now supports VLAN-compatible MTU and an MTU size which
          is larger than 1500.</para>

        <para revision="212320">The &man.ng.ether.4; &man.netgraph.4;
          node now supports interface transfer between multiple virtual
          network stacks by &man.ifconfig.8; <command>vnet</command>
          command.  A &man.ng.ether.4; node associated with a network
          interface is now destroyed and recreated when the network
          interface is moved to another vnet.</para>

        <para revision="209843">A new &man.netgraph.4; node
          &man.ng.patch.4; has been added.  This performs data
          modification of packets passing through.  Modifications are
          restricted to a subset of C language operations on unsigned
          integers of 8, 16, 32 or 64-bit size.</para>

        <para revision="212905">An ICMP unreachable problem in the
          &man.pf.4; packet filter subsystem when TSO support is
          enabled has been fixed.</para>

        <para revision="211538">The TCP bandwidth delay product window
          limiting algorithm controlled by the &man.sysctl.8; variable
          <varname>net.inet.tcp.inflight.enable</varname> is now
          disabled by default.  It has been found that this algorithm
          is inefficient on a fast network with smaller RTT than 10ms.
          It had been enabled by default since 5.2-RELEASE, and then
          had been disabled only if the RTT was lesser than 10ms since
          7.0-RELEASE.  Pluggable TCP congestion control algorithm
          modules are planned to be added for the future
          releases.</para>

        <para revision="211602">A bug in &os; TCP Path MTU discovery
          which could lead to a wrong calculation for an MTU smaller
          than 256 octets has been fixed.  Note that this bug did not
          affect MTUs equal to or larger than 256 octets.</para>

        <para revision="214865,214866">The &os; TCP reassembly
          implementation has been improved.  A long-standing
          accounting bug affecting SMP systems has been fixed and the
          <varname>net.inet.tcp.reass.maxqlen</varname> &man.sysctl.8;
          variable has been retired in favor of a per-connection
          dynamic limit based on the receive socket buffer size.  &os;
          receivers now handle packet loss (particularly losses caused
          by queue overflows) significantly better than before which
          improves connection throughput.</para>

        <para revision="211870">The TCP initial window increase in RFC
          3390 which can be controlled by a &man.sysctl.8; variable
          <varname>net.inet.tcp.rfc3390</varname> now reduces the
          congestion window to the restart window if a TCP connection
          has been idle for one retransmit timeout or more.  For more
          details, see RFC 5681 Section 4.1.</para>

        <para revision="214859">The &man.siftr.4;, Statistical
          Information For TCP Research (SIFTR) kernel module has been
          added.  This is a facility that logs a range of statistics
          on active TCP connections to a log file.  It provides the
          ability to make highly granular measurements of TCP
          connection state, aimed at system administrators, developers
          and researchers.</para>

        <para revision="212319">&os; virtual network stack (vnet) now
          supports IPv4 multicast routing.</para>

        <para revision="239616">The IEEE 802.11s element identifiers have
          been updated to reflect the final version of the amendment.  This
          update breaks compatibility with older mesh setups but is necessary
          as the previous IDs are used by another amendment leading to
          unexpected results when trying to associate with an accesspoint
          using the affected IDs.</para>
      </sect3>

      <sect3 xml:id="disks">
        <title>Disks and Storage</title>

        <para revision="211458">The &man.ahci.4; driver now disables NCQ
          and PMP support on VIA VT8251 because they are unreliable
          under load.</para>

        <para revision="211718">The &man.ahci.4; driver now uses 15
          seconds for device reset timeout instead of 10 seconds
          because some devices need 10 - 12 seconds to spin up.</para>

        <para revision="215825">The &man.arcmsr.4; driver
          has been updated to version 1.20.00.19.</para>

        <para revision="215173">The &man.ada.4; driver now supports a
          new &man.sysctl.8; variable
          <varname>kern.cam.ada.spindown_shutdown</varname> which
          controls whether or not to spin-down disks when shutting
          down if the device supports the functionality.  The default
          value is <literal>1</literal>.</para>

        <para revision="210164">The &man.ata.4; driver
          now supports limiting initial ATA mode for devices via
          device hints
          <varname>hint.<replaceable>devname</replaceable>.<replaceable>unit</replaceable>.dev<replaceable>N</replaceable
          >.mode</varname> or
          <varname>hint.<replaceable>devname</replaceable>.<replaceable>unit</replaceable>.mode</varname>.
          The valid values are the same as ones supported in the
          &man.atacontrol.8; and &man.camcontrol.8; utilities.</para>

        <para revision="210204">The &man.ata.4; driver now disables
          cable status check on both controller and device side
          when the loader tunable
          <varname>hw.ata.ata_dma_check_80pin</varname> is
          <literal>0</literal>.  The check on controller side was
          performed regardless of this loader tunable.</para>

        <para revision="215777">The &man.ata.4; driver now reports
          SATA power management capabilities to the &man.CAM.4; layer when
          <option>ATA_CAM</option> is enabled.  This allows a device
          to initiate transitions if controller configured to accept
          it.  This makes
          <varname>hint.ata.<replaceable>N</replaceable>.pm_level=1</varname>
          mode work.</para>

        <para revision="214671">The &man.ata.4; driver has been
          improved on hotplugging and connection speed reporting
          support for some Intel SATA controllers including ICH5 and
          ICH8+ operating in legacy mode.</para>

        <para revision="213291">An issue of device detection of
          Serverworks K2 SATA controllers in the &man.ata.4; has been fixed.</para>

        <para revision="214667">A bug in the &man.ata.4; driver that
          prevented some Silicon Image chipsets from working on big
          endian systems has been fixed.</para>

        <para revision="214330">The &man.gconcat.8; GEOM class now
          supports kernel crash dump.  The dumping is performed to the
          component where a dump partition begins.</para>

        <para revision="214405">A bug in the &man.geli.8; GEOM class
          on little endian platforms has been fixed.  The metadata
          version for newly created providers has been updated to
          <literal>4</literal> due to this.  Providers with the older
          versions are fully interoperable with 8.2-RELEASE and later
          by being treated as ones with the native byte order flag
          automatically.</para>

        <para revision="214405">The &man.geli.8; GEOM class now
          supports a &man.sysctl.8; variable
          <varname>kern.geom.eli.overwrites</varname>.  This specifies
          the number of times on-disk keys should be overwritten when
          destroying them.  The default value is
          <literal>5</literal>.</para>

        <para revision="214405">The &man.geli.8; GEOM class has been
          improved for preventing the same encryption key from being
          used in 2^20 blocks (sectors).</para>

        <para revision="214405">The &man.geli.8; GEOM class now uses
          XTS-AES mode by default.</para>

        <para revision="214405">A &man.sysctl.8; variable
          <varname>kern.geom.eli.debug</varname> now allows a value
          <literal>-1</literal>.  This means turn off any log messages
          of the &man.geli.8; GEOM class.</para>

        <para revision="210376">The &man.mpt.4; driver now supports
          larger I/O sizes which the device and &man.CAM.4; subsystem
          can support.  This was limited to 64KB, and the number of
          scatter/gather segments was limited to 33 on platforms with
          4K pages.</para>

        <para revision="209404">The &man.twa.4;
          driver has been updated.  The version number is
          3.80.06.003.</para>
      </sect3>

      <sect3 xml:id="fs">
        <title>File Systems</title>

        <para revision="214050">The &man.linprocfs.5; Linux process
          file system now supports
          <filename>proc/$$/environment</filename>.</para>

        <para revision="212716">The &os; NFS client now supports a
          kernel environment variable
          <varname>boot.nfsroot.nfshandlelen</varname>.  This lets the
          diskless root file system on boot to use NFS version 3 and
          the specified file handle length.  If this variable is not
          set, NFS version 2 is used.</para>

        <para revision="212668">The ZFS on-disk format has been updated
          to version 15.</para>

        <para revision="212671">The ZFS metaslab code has been updated.
          This provides a noticeable improvement on write speed,
          especially on pools with less than 30% of free space.  The
          related OpenSolaris Bug IDs are 6826241, 6869229, 6918420,
          and 6917066.</para>

        <para revision="214013">The ZFS now supports offlining of log
          devices.  The related OpenSolaris Bug IDs are 6599442,
          6726045, and 6803605.</para>

        <para revision="212672">Performance improvements for the ZFS
          have been imported from OpenSolaris.  They include caching of
          ACL permission checks, faster handling of &man.stat.2;,
          mitigation of mutex lock contention.  The related
          OpenSolaris Bug IDs are 6802734, 6844861, 6848431, 6775100,
          6827779, 6857433, 6860318, 6865875, 6867395, 6868276, and
          6870564.</para>

        <para revision="210541">The default value of
          <varname>vfs.zfs.vdev.max_pending</varname> has been
          decreased from 35 to 10 (OpenSolaris Bug ID is 6891731) to
          improve latency.</para>

        <para>Various bugs in the ZFS subsystem have been fixed.  The
          related OpenSolaris Bug IDs are: 6328632, 6396518, 6501037,
          6504953, 6542860, 6551866, 6572357, 6572376, 6582163,
          6586537, 6595194, 6596237, 6604992, 6621164, 6623978,
          6633095, 6635482, 6664765, 6674216, 6696242, 6696858,
          6702206, 6710376, 6713916, 6717022, 6722540, 6722991,
          6737463, 6739487, 6739553, 6740164, 6745863, 6747596,
          6747698, 6748436, 6755435, 6757430, 6758107, 6759986,
          6759999, 6761100, 6761406, 6764124, 6765294, 6767129,
          6769612, 6770866, 6774713, 6774886, 6775697, 6776104,
          6776548, 6780491, 6784104, 6784108, 6785914, 6788152,
          6788830, 6789318, 6790064, 6790345, 6790687, 6791064,
          6791066, 6791071, 6791101, 6792134, 6792139, 6792884,
          6793430, 6794136, 6794570, 6794830, 6797109, 6797118,
          6798384, 6798878, 6799895, 6800184, 6800942, 6801507,
          6801810, 6803343, 6803822, 6804954, 6807339, 6807765,
          6809340, 6809683, 6809691, 6810367, 6815592, 6815893,
          6816124, 6818183, 6821169, 6821170, 6822816, 6824006,
          6824062, 6824968, 6826466, 6826468, 6826469, 6826470,
          6826471, 6826472, 6827260, 6830237, 6830541, 6833162,
          6833711, 6833999, 6834217, 6836714, 6836768, 6838062,
          6838344, 6841321, 6843014, 6843069, 6843235, 6844069,
          6844900, 6847229, 6848242, 6856634, 6857012, 6861983,
          6862984, 6863610, 6870564, 6880764, 6882227, 6892298,
          6898245, 6906110, 6906946, 6939941, 6950219, 6951024, and
          6953403.</para>
      </sect3>
    </sect2>

    <sect2 xml:id="userland">
      <title>Userland Changes</title>

      <para revision="209267">The &man.arp.8; utility has been improved.
        It now runs faster even when a single interface has a number
        of aliases.</para>

      <para revision="214729">A bug in the &man.b64decode.1; utility that
        prevented an <option>-r</option> option from handling arbitrary
        breaks in a base64 encoded string has been fixed.</para>

      <para revision="211723">The &man.calendar.1; utility now supports
        repeating events which span multiple years, lunar events, and
        solar events.</para>

      <para revision="210915">The &man.dhclient.8; utility now reports a
        reason for exiting and the 10-second period in which the
        &man.dhclient.8; ignores routing messages has been changed to
        start just after <filename>dhclient-script</filename> starts
        instead of just after it finished.  This change fixes a
        symptom that &man.dhclient.8; silently exits under a certain
        condition.</para>

      <para revision="214983">Userland support for the &man.dtrace.1;
        subsystem has been added.  This allows inspection of userland
        software itself and its correlation with the kernel, thus
        allowing a much better picture of what exactly is going on
        behind the scenes.  The &man.dtruss.1; utility has been added
        and the <filename>libproc</filename> library has been updated
        to support the facility.</para>

      <para revision="209362">The &man.du.1; utility now supports a
        <option>-t <replaceable>threshold</replaceable></option>
        option to display entries that exceeds the value of
        <replaceable>threshold</replaceable>.  If the value is
        negative, it displays entries with a value less than the
        absolute value of <replaceable>threshold</replaceable>.</para>

      <para revision="215667">The &man.fdisk.8; utility now supports
        partitions which are provided by &man.gjournal.8; or
        &man.geli.8; GEOM classes.</para>

      <para revision="210567">The &man.gcore.1; utility now supports an
        <option>-f</option> flag which forces a full dump of all the
        segments except for the malformed ones.</para>

      <para revision="214405">The &man.geli.8; utility now supports
        <command>resize</command> subcommand to resize encrypted file
        systems after growing it.</para>

      <para revision="214405">The &man.geli.8; utility now supports
        <command>suspend</command> and <command>resume</command>
        subcommands.  The <command>suspend</command> subcommand makes
        &man.geli.8; devices wait for all in-flight I/O requests,
        suspend new I/O requests, remove all &man.geli.8; sensitive
        data from the kernel memory (like encryption keys) and will
        wait for either <command>geli resume</command> or
        <command>geli detach</command> command.  For more
        information, see &man.geli.8; manual page.</para>

      <para revision="214405">The &man.geli.8; utility now checks the
        metadata provider size strictly.  If the check fails, the
        provider is not attached.  A new option <option>-f</option>
        can override this behavior.</para>

      <para revision="214405">The &man.geli.8; utility now supports
        <option>-J <replaceable>newpassfile</replaceable></option> and
        <option>-j <replaceable>oldpassfile</replaceable></option>
        options for loading passphrase from a file.</para>

      <para revision="211938">The <function>gethost*()</function>,
        <function>getnet*()</function>, and
        <function>getproto*()</function> functions now set the errno
        to <literal>ERANGE</literal> and the NSS backend terminates
        with <literal>NS_RETURN</literal> when the result buffer size
        is too small.</para>

      <para revision="209497">The &man.gpart.8; utility now supports a
        <command>resize</command> command to resize partitions for all
        schemes but EBR.</para>

      <para revision="215941">The &man.gpart.8; utility now supports
        <command>backup</command> and <command>restore</command>
        subcommands to backup partition tables and restore
        them.</para>

      <para revision="213661">The &man.gpart.8; utility now handles
        given geom/provider names with and without
        <filename>/dev/</filename> prefix.</para>

      <para revision="213684">The &man.gpart.8; utility now supports
        an <option>-F</option> option for the
        <command>destroy</command> subcommand.  This option forces
        destroying of the partition table even if it is not
        empty.</para>

      <para revision="213684">The &man.gpart.8; utility now supports a
        <command>recover</command> subcommand for GPT partition
        tables.  A corrupted GPT is now marked when the following
        three types of corruption:</para>

      <itemizedlist>
        <listitem>
          <para>Primary GPT header or table is corrupted.</para>
        </listitem>

        <listitem>
          <para>Secondary GPT header or table is corrupted.</para>
        </listitem>

        <listitem>
          <para>Secondary GPT header is not located at the last LBA.</para>
        </listitem>
      </itemizedlist>

      <para>Changes to the corrupted GPT table are not allowed except
        for <command>destroy</command> and <command>recover</command>
        subcommands.</para>

      <para revision="213994">The &man.gpart.8; utility now supports
        <literal>GPT_ENT_ATTR_BOOTME</literal>,
        <literal>GPT_ENT_ATTR_BOOTONCE</literal>, and
        <literal>GPT_ENT_ATTR_BOOTFAILED</literal> attributes in GPT.
        The attribute keywords in the command line are
        <literal>bootme</literal>, <literal>bootonce</literal>, and
        <literal>bootfailed</literal> respectively.</para>

      <para revision="215728">An issue in the &man.newfs.8; utility
        has been fixed.  A UFS1 file system created with 64KB
        blocksize was incorrectly recognized as one with a broken
        superblock.  This is because the &os; kernel checks a
        partition first for a UFS2 superblock at 64KB offset while it
        is possible that a UFS1 file systems with 64KB blocksize has
        an alternative superblock at the same location.  For example,
        a file system created by <command>newfs -U -O 1 -b 65536 -f
        8192</command> could lead to this symptom.</para>

      <para revision="213049">The &man.hastd.8; utility now supports
        <literal>SIGHUP</literal> for reloading the configuration
        file.  When <literal>SIGTERM</literal> or
        <literal>SIGINT</literal> is received, the worker processes
        terminate.</para>

      <para revision="212144">The &man.ifconfig.8; utility now check an
        invalid CIDR subnet notation more strictly.  It wrongly
        accepted <literal>10.0.0.1/10.0.0.1</literal> as
        <literal>10.0.0.1/10</literal>.</para>

      <para revision="215237">An accuracy issue in the &man.jn.3; and
        &man.jnf.3; functions in <filename>libm</filename> has been
        fixed.</para>

      <para revision="209284">Incorrect behaviors in stuttering
        sequences and reverse ranges in the &man.jot.1; utility have
        been fixed.</para>

      <para revision="213667">The <filename>libarchive</filename>
        library and &man.tar.1; utility now support LZMA
        (Lempel-Ziv-Markov chain-Algorithm) compression format.</para>

      <para revision="215229">The &man.tar.1; utility now supports a
        blocksize which is up to <literal>8192</literal> (4MB) in the
        <option>-b <replaceable>blocksize</replaceable></option>
        option.</para>

      <para revision="214442">A bug in the &man.lpr.1; utility that
        prevented it from working with some files on a ZFS file system
        has been fixed.</para>

      <para revision="213978">The <option>-p</option> option in the
        &man.mount.8; utility now displays the <literal>rw</literal>
        mount option correctly as in the &man.fstab.5; format.</para>

      <para revision="213889">The &man.ncal.1; utility has been
        updated.  The option <option>-b</option> has been replaced
        with <option>-C</option> and <option>-B
        <replaceable>number</replaceable></option>.  Options
        <option>-3</option> to show previous, current and next month, and
        <option>-A <replaceable>number</replaceable></option> to show
        months after current month have been added.  The option
        <option>-m <replaceable>N</replaceable>
        <replaceable>YYYY</replaceable></option> now prints only the
        month, not the whole year.</para>

      <para revision="211699">The &man.newsyslog.8; utility now supports
        an <option>-S <replaceable>pidfile</replaceable></option>
        option to override the default &man.syslogd.8; PID
        file.</para>

      <para revision="215622">The &man.newsyslog.8; utility now
        supports a special log file name
        <literal>&lt;include&gt;</literal> for processing file
        inclusion.  Globbing in the file name and circular dependency
        detection are supported.  For more details, see
        the &man.newsyslog.conf.5; manual page.</para>

      <para revision="213980">The &man.ntpd.8; utility is now compiled
        with shared memory reference clock driver.  For example, GPS
        devices can be used as source of precise time via <filename
        role="ports">astro/gpsd</filename> in the Ports
        Collection.</para>

      <para revision="212848">An off-by-one error in the &man.pax.1;
        utility when ustar file name is too long has been
        fixed.</para>

      <para revision="209912">The &man.pkill.1; utility now supports
        an <option>-l</option> option like the &man.kill.1; utility
        does.</para>

      <para revision="211098">The &man.pmcstat.8; utility now supports a
        file and a network socket as a top source.  A new option
        <option>-O <replaceable>filename</replaceable></option>
        specifies to send log output to
        <replaceable>filename</replaceable>, and another new option
        <option>-R <replaceable>filename</replaceable></option>
        specifies to receive events from
        <replaceable>filename</replaceable>.  For a socket, the
        <replaceable>filename</replaceable> is in a form of
        <replaceable>ipaddr:port</replaceable>.  This allows top
        monitoring over TCP on a system with no local symbols, for
        example.</para>

      <para revision="210089">The &man.pom.6; utility now
        supports a <option>-p</option> flag to print only the
        percentage.</para>

      <para revision="212472">The &man.powerd.8; utility now supports
        an <option>-m <replaceable>freq</replaceable></option> and
        <option>-M <replaceable>freq</replaceable></option> to control
        the minimum and maximum frequency, respectively.</para>

      <para revision="213825">The &man.ruptime.1; utility now displays
        hostnames longer than 12 characters.</para>

      <para revision="215066">A behavior of the &man.sh.1; program
        when an <option>-u</option> option is specified has been
        changed.  The special parameters <varname>$@</varname> and
        <varname>$*</varname> no longer cause an error when there are
        no positional parameters.</para>

      <para revision="210616">A bug in the &man.sh.1; program has been
        fixed.  A <literal>SIGINT</literal> signal is now passed
        through from a child process if the shell is interactive and
        the job control is enabled.  For example, aborting
        &man.sleep.1; command by Ctrl-C no longer display
        <literal>ok</literal> in the following command line:</para>

      <screen>&prompt.user; sleep 5; echo ok</screen>

      <para revision="210732">The &man.sh.1; program now supports a
        <command>bg</command> command consisting solely of
        redirections.  For example:</para>

      <screen>&prompt.user; &lt; /dev/null &amp;</screen>

      <para revision="211536">The &man.sleep.1; utility now supports
        the <literal>SIGINFO</literal> signal and reports the specified
        sleep time and the remaining time.</para>

      <para revision="213036,213038">The &man.tftp.1; and &man.tftpd.8;
        utilities have been improved for better interoperability and
        they now support RFC 1350, 2347, 2348, 2349, and 3617.</para>

      <para revision="213899">A bug in <literal>[=]=]</literal>
        equivalent class handling in the &man.tr.1; utility has been
        fixed.  A closing bracket immediately after
        <literal>[=</literal> was incorrectly treated as
        special.</para>

      <para revision="210566">The &man.uname.1; utility now supports an
        <option>-o</option> flag as a synonym for the
        <option>-s</option> flag for compatibility with other
        systems.</para>

      <para revision="211060">Bugs in &man.vi.1; utility have been
        fixed.  They include handling of <literal>^@</literal> and
        <literal>^C</literal> in insert mode when reading an ex
        command.</para>

      <para revision="214345">The &man.watchdogd.8; program now uses
        <literal>MADV_PROTECT</literal> memory flag to protect itself
        from being terminated by the &os; kernel when available memory
        becomes short.  This kind of process termination happens in a
        swap-intensive workload.</para>

      <para revision="209870">The <command>set sharenfs</command>
        command in the &man.zfs.8; utility now supports
        <option>sec</option> option.</para>

      <sect3 xml:id="periodic-scripts">
        <title><filename>/etc/periodic</filename> Scripts</title>

        <para>A periodic script for <command>zfs scrub</command> has
          been added.  For more details, see &man.periodic.conf.5;
          manual page.</para>

        <para>A periodic script which can be used to find installed
          ports' files with mismatched checksum has been added. For more
          details, see the &man.periodic.conf.5; manual page.</para>
      </sect3>
    </sect2>

    <sect2 xml:id="contrib">
      <title>Contributed Software</title>

      <para>The <application>ACPI-CA</application> has been updated to
        20101013.</para>

      <para revision="214287">The &man.ee.1; program has been updated
        to version 1.5.2.</para>

      <para><application>ISC BIND</application> has been updated to
        version 9.6-ESV-R3.</para>

      <para><application>netcat</application> has been updated to
        version 4.8.</para>

      <para><application>OpenSSL</application> has been updated to
        version 0.9.8q.</para>

      <para revision="285374"><application>sendmail</application> has
        been updated to version 8.15.2.</para>

      <para>The <application>timezone</application> database has been
        updated to the <application>tzdata2010o</application>
        release.</para>

      <para>The <application>xz</application> has been updated
        from snapshot as of 12 April 2010 to 5.0.0 release</para>
    </sect2>

    <sect2 xml:id="ports">
      <title>Ports/Packages Collection Infrastructure</title>

      <para revision="215738">The &man.pkg.create.1; utility now supports LZMA
        (<application>xz</application>) compression.  Note that the
        default is still <application>bzip2</application>.</para>
    </sect2>

    <sect2 xml:id="releng">
      <title>Release Engineering and Integration</title>

      <para revision="211007">The &man.sysinstall.8; utility now uses
        the following numbers for default and minimum partition sizes:
        1GB for <filename>/</filename>, 4GB for
        <filename>/var</filename>, and 1GB for
        <filename>/tmp</filename>.</para>

      <para revision="211009">The &man.sysinstall.8; utility now
        attempts to enable &man.getty.8; on a serial port when no VGA
        card is detected on the system.</para>

      <para>The supported version of
        the <application>GNOME</application> desktop environment
        (<package>x11/gnome2</package>) has been
        updated to 2.32.1.</para>

      <para>The supported version of
        the <application>KDE</application> desktop environment
        (<package>x11/kde4</package>) has been
        updated to 4.5.5.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="upgrade">
    <title>Upgrading from previous releases of &os;</title>

    <para arch="amd64,i386">Upgrades between RELEASE versions (and
      snapshots of the various security branches) are supported using
      the &man.freebsd-update.8; utility.  The binary upgrade
      procedure will update unmodified userland utilities, as well as
      unmodified GENERIC kernel distributed as a part of an
      official &os; release.  The &man.freebsd-update.8; utility
      requires that the host being upgraded has Internet
      connectivity.</para>

    <para>An older form of binary upgrade is supported through the
      <command>Upgrade</command> option from the main
      &man.sysinstall.8; menu on CDROM distribution media.  This type
      of binary upgrade may be useful on non-&arch.i386;,
      non-&arch.amd64; machines or on systems with no Internet
      connectivity.</para>

    <para>Source-based upgrades (those based on recompiling the &os;
      base system from source code) from previous versions are
      supported, according to the instructions in
      <filename>/usr/src/UPDATING</filename>.</para>

    <important>
      <para>Upgrading &os; should, of course, only be attempted after
        backing up <emphasis>all</emphasis> data and configuration
        files.</para>
    </important>
  </sect1>
</article>