1 .\" Copyright (c) 2000, 2003 Robert N. M. Watson
2 .\" Copyright (c) 2008-2012 James Gritton
3 .\" All rights reserved.
5 .\" Redistribution and use in source and binary forms, with or without
6 .\" modification, are permitted provided that the following conditions
8 .\" 1. Redistributions of source code must retain the above copyright
9 .\" notice, this list of conditions and the following disclaimer.
10 .\" 2. Redistributions in binary form must reproduce the above copyright
11 .\" notice, this list of conditions and the following disclaimer in the
12 .\" documentation and/or other materials provided with the distribution.
14 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 .Nd "manage system jails"
41 .Ar param Ns = Ns Ar value ...
42 .Op Cm command Ns = Ns Ar command ...
53 .Op Cm * | Ar jail ...
60 .Op Fl s Ar securelevel
61 .Ar path hostname ip Ns Op Cm \&, Ns Ar ...
70 utility creates new jails, or modifies or removes existing jails.
71 It can also print a list of configured jails and their parameters.
74 is specified via parameters on the command line, or in the
78 At least one of the options
85 These options are used alone or in combination to describe the operation to
87 .Bl -tag -width indent
94 parameters (if specified on the command line)
95 must not refer to an existing jail.
97 Exhibit a list of all configured non-wildcard jails and their parameters.
98 No jail creation, modification or removal performed if this option is used.
101 string is used to separate parameters.
104 utility to list running jails.
106 Modify an existing jail.
111 parameters must exist and refer to an existing jail.
112 Some parameters may not be changed on a running jail.
116 specified by jid or name.
117 All jailed processes are killed, and all jails that are
118 children of this jail are also
121 Restart an existing jail.
122 The jail is first removed and then re-created, as if
126 were run in succession.
128 Create a jail if it does not exist, or modify the jail if it does exist.
130 Modify an existing jail.
131 The jail may be restarted if necessary to modify parameters than could
132 not otherwise be changed.
134 Create a jail if it doesn't exist, or modify (and possibly restart) the
135 jail if it does exist.
138 Other available options are:
139 .Bl -tag -width indent
141 Allow making changes to a dying jail, equivalent to the
144 .It Fl f Ar conf_file
145 Use configuration file
147 instead of the default
154 and add all IP addresses returned by the resolver
155 to the list of addresses for this jail.
156 This is equivalent to the
160 Output (only) the jail identifier of the newly created jail(s).
167 file, containing the parameters used to start the jail.
169 Run commands in a clean environment.
170 This is deprecated and is equivalent to the exec.clean parameter.
173 This is deprecated and is equivalent to the
177 Limit the number of commands from
179 that can run simultaneously.
181 Suppress the message printed whenever a jail is created, modified or removed.
182 Only error messages will be printed.
186 option that removes an existing jail without using the configuration file.
187 No removal-related parameters for this jail will be used \(em the jail will
189 .It Fl s Ar securelevel
192 MIB entry to the specified value inside the newly created jail.
193 This is deprecated and is equivalent to the
197 The user name from host environment as whom jailed commands should run.
198 This is deprecated and is equivalent to the
201 .Va exec.system_jail_user
204 The user name from the jailed environment as whom jailed commands should run.
205 This is deprecated and is equivalent to the
209 Print a message on every operation, such as running commands and
210 mounting filesystems.
213 If no arguments are given after the options, the operation (except
214 remove) will be performed on all jails specified in the
217 A single argument of a jail name will operate only on the specified jail.
222 options can also remove running jails that aren't in the
224 file, specified by name or jid.
228 is a wildcard that will operate on all jails, regardless of whether
231 this is the surest way for
234 If hierarchical jails exist, a partial-matching wildcard definition may
236 For example, an argument of
238 would apply to jails with names like
243 A jail may be specified with parameters directly on the command line.
246 file will not be used.
247 For backward compatibility, the command line may also have four fixed
248 parameters, without names:
254 This mode will always create a new jail, and the
258 options do not apply (and must not be present).
262 file, or on the command line, are generally of the form
264 Some parameters are boolean, and do not have a value but are set by the
265 name alone with or without a
271 They can also be given the values
275 Other parameters may have more than one value, specified as a
276 comma-separated list or with
278 in the configuration file (see
284 utility recognizes two classes of parameters.
285 There are the true jail
286 parameters that are passed to the kernel when the jail is created,
287 which can be seen with
289 and can (usually) be changed with
291 Then there are pseudo-parameters that are only used by
295 Jails have a set of core parameters, and kernel modules can add their own
297 The current set of available parameters can be retrieved via
298 .Dq Nm sysctl Fl d Va security.jail.param .
299 Any parameters not set will be given default values, often based on the
301 The core parameters are:
302 .Bl -tag -width indent
305 This will be assigned automatically to a new jail (or can be explicitly
306 set), and can be used to identify the jail for later modification, or
313 This is an arbitrary string that identifies a jail (except it may not
318 it can be passed to later
326 is supplied, a default is assumed that is the same as the
330 parameter is implied by the
332 file format, and need not be explicitly set when using the configuration
335 The directory which is to be the root of the jail.
336 Any commands run inside the jail, either by
340 are run from this directory.
342 A list of IPv4 addresses assigned to the jail.
343 If this is set, the jail is restricted to using only these addresses.
344 Any attempts to use other addresses fail, and attempts to use wildcard
345 addresses silently use the jailed address instead.
346 For IPv4 the first address given will be used as the source address
347 when source address selection on unbound sockets cannot find a better
349 It is only possible to start multiple jails with the same IP address
350 if none of the jails has more than this single overlapping IP address
353 A boolean option to change the formerly mentioned behaviour and disable
354 IPv4 source address selection for the jail in favour of the primary
355 IPv4 address of the jail.
356 Source address selection is enabled by default for all jails and the
358 setting of a parent jail is not inherited for any child jails.
360 Control the availability of IPv4 addresses.
363 to allow unrestricted access to all system addresses,
365 to restrict addresses via
369 to stop the jail from using IPv4 entirely.
372 parameter implies a value of
374 .It Va ip6.addr , Va ip6.saddrsel , Va ip6
375 A set of IPv6 options for the jail, the counterparts to
382 Create the jail with its own virtual network stack,
383 with its own network interfaces, addresses, routing table, etc.
384 The kernel must have been compiled with the
386 for this to be available.
389 to use the system network stack, possibly with restricted IP addresses,
392 to create a new network stack.
394 The hostname of the jail.
395 Other similar parameters are
396 .Va host.domainname ,
401 Set the origin of hostname and related information.
404 to use the system information and
406 for the jail to use the information from the above fields.
407 Setting any of the above fields implies a value of
410 The value of the jail's
413 A jail never has a lower securelevel than its parent system, but by
414 setting this parameter it may have a higher one.
415 If the system securelevel is changed, any jail securelevels will be at
418 The number of the devfs ruleset that is enforced for mounting devfs in
420 A value of zero (default) means no ruleset is enforced.
421 Descendant jails inherit the parent jail's devfs ruleset enforcement.
422 Mounting devfs inside a jail is possible only if the
425 .Va allow.mount.devfs
426 permissions are effective and
428 is set to a value lower than 2.
429 Devfs rules and rulesets cannot be viewed or modified from inside a jail.
431 NOTE: It is important that only appropriate device nodes in devfs be
432 exposed to a jail; access to disk devices in the jail may permit processes
433 in the jail to bypass the jail sandboxing by modifying files outside of
437 for information on how to use devfs rules to limit access to entries
438 in the per-jail devfs.
439 A simple devfs ruleset for jails is available as ruleset #4 in
440 .Pa /etc/defaults/devfs.rules .
442 The number of child jails allowed to be created by this jail (or by
443 other jails under this jail).
444 This limit is zero by default, indicating the jail is not allowed to
447 .Sx "Hierarchical Jails"
448 section for more information.
450 The number of descendants of this jail, including its own child jails
451 and any jails created under them.
452 .It Va enforce_statfs
453 This determines what information processes in a jail are able to get
455 It affects the behaviour of the following syscalls:
461 (as well as similar compatibility syscalls).
462 When set to 0, all mount points are available without any restrictions.
463 When set to 1, only mount points below the jail's chroot directory are
465 In addition to that, the path to the jail's chroot directory is removed
466 from the front of their pathnames.
467 When set to 2 (default), above syscalls can operate only on a mount-point
468 where the jail's chroot directory is located.
470 Setting this boolean parameter allows a jail to exist without any
472 Normally, a command is run as part of jail creation, and then the jail
473 is destroyed as its last process exits.
474 A new jail must have either the
480 pseudo-parameter set.
482 The ID of the cpuset associated with this jail (read-only).
484 This is true if the jail is in the process of shutting down (read-only).
488 of the parent of this jail, or zero if this is a top-level jail
491 The string for the jail's
495 The number for the jail's
499 Some restrictions of the jail environment may be set on a per-jail
501 With the exception of
502 .Va allow.set_hostname
504 .Va allow.reserved_ports ,
505 these boolean parameters are off by default.
506 .Bl -tag -width indent
507 .It Va allow.set_hostname
508 The jail's hostname may be changed via
513 A process within the jail has access to System V IPC primitives.
514 This is deprecated in favor of the per-module parameters (see below).
515 When this parameter is set, it is equivalent to setting
522 .It Va allow.raw_sockets
523 The jail root is allowed to create raw sockets.
524 Setting this parameter allows utilities like
528 to operate inside the jail.
529 If this is set, the source IP addresses are enforced to comply
530 with the IP address bound to the jail, regardless of whether or not
533 flag has been set on the socket.
534 Since raw sockets can be used to configure and interact with various
535 network subsystems, extra caution should be used where privileged access
536 to jails is given out to untrusted parties.
538 Normally, privileged users inside a jail are treated as unprivileged by
540 When this parameter is set, such users are treated as privileged, and
541 may manipulate system file flags subject to the usual constraints on
542 .Va kern.securelevel .
544 privileged users inside the jail will be able to mount and unmount file
545 system types marked as jail-friendly.
548 command can be used to find file system types available for mount from
550 This permission is effective only if
552 is set to a value lower than 2.
553 .It Va allow.mount.devfs
554 privileged users inside the jail will be able to mount and unmount the
556 This permission is effective only together with
560 is set to a value lower than 2.
561 The devfs ruleset should be restricted from the default by using the
565 The jail root may administer quotas on the jail's filesystem(s).
566 This includes filesystems that the jail may share with other jails or
567 with non-jailed parts of the system.
568 .It Va allow.read_msgbuf
569 Jailed users may read the kernel message buffer.
571 .Va security.bsd.unprivileged_read_msgbuf
572 MIB entry is zero, this will be restricted to the root user.
573 .It Va allow.socket_af
574 Sockets within a jail are normally restricted to IPv4, IPv6, local
575 (UNIX), and route. This allows access to other protocol stacks that
576 have not had jail functionality added to them.
578 Locking or unlocking physical pages in memory are normally not available
580 When this parameter is set, users may
585 .Va security.bsd.unprivileged_mlock
595 daemons are permitted to run inside a properly configured vnet-enabled jail.
596 The jail's root must be a file system mount point and
598 must not be set to 0, so that
600 can export file systems visible within the jail.
602 must be set to 1 if file systems mounted under the
603 jail's file system need to be exported by
605 For exporting only the jail's file system, a setting of 2
607 If the kernel configuration does not include the
611 must be loaded outside of the jails.
612 This is normally done by adding
618 file outside of the jails.
621 is to be run in a jail, either the kernel
623 option needs to be specified or
631 file outside of the jails.
632 .It Va allow.reserved_ports
633 The jail root may bind to ports lower than 1024.
634 .It Va allow.unprivileged_proc_debug
635 Unprivileged processes in the jail may use debugging facilities.
637 The value of the jail's
638 .Va security.bsd.suser_enabled
640 The super-user will be disabled automatically if its parent system has it
642 The super-user is enabled by default.
646 Kernel modules may add their own parameters, which only exist when the
648 These are typically headed under a parameter named after the module,
651 to give the jail full use of the module,
653 to encapsulate the jail in some module-specific way,
656 to make the module unavailable to the jail.
657 There also may be other parameters to define jail behavior within the module.
658 Module-specific parameters include:
659 .Bl -tag -width indent
660 .It Va allow.mount.fdescfs
661 privileged users inside the jail will be able to mount and unmount the
663 This permission is effective only together with
667 is set to a value lower than 2.
668 .It Va allow.mount.fusefs
669 privileged users inside the jail will be able to mount and unmount
670 fuse-based file systems.
671 This permission is effective only together with
675 is set to a value lower than 2.
676 .It Va allow.mount.nullfs
677 privileged users inside the jail will be able to mount and unmount the
679 This permission is effective only together with
683 is set to a value lower than 2.
684 .It Va allow.mount.procfs
685 privileged users inside the jail will be able to mount and unmount the
687 This permission is effective only together with
691 is set to a value lower than 2.
692 .It Va allow.mount.linprocfs
693 privileged users inside the jail will be able to mount and unmount the
694 linprocfs file system.
695 This permission is effective only together with
699 is set to a value lower than 2.
700 .It Va allow.mount.linsysfs
701 privileged users inside the jail will be able to mount and unmount the
702 linsysfs file system.
703 This permission is effective only together with
707 is set to a value lower than 2.
708 .It Va allow.mount.tmpfs
709 privileged users inside the jail will be able to mount and unmount the
711 This permission is effective only together with
715 is set to a value lower than 2.
716 .It Va allow.mount.zfs
717 privileged users inside the jail will be able to mount and unmount the
719 This permission is effective only together with
723 is set to a value lower than 2.
726 for information on how to configure the ZFS filesystem to operate from
731 This flag is only available when the
733 kernel module is loaded.
735 Determine how a jail's Linux emulation environment appears.
738 will keep the same environment, and
740 will give the jail its own environment (still originally inherited when
741 the jail is created).
742 .It Va linux.osname , linux.osrelease , linux.oss_version
743 The Linux OS name, OS release, and OSS version associated with this jail.
745 Allow access to SYSV IPC message primitives.
748 all IPC objects on the system are visible to this jail, whether they
749 were created by the jail itself, the base system, or other jails.
752 the jail will have its own key namespace, and can only see the objects
754 the system (or parent jail) has access to the jail's objects, but not to
758 the jail cannot perform any sysvmsg-related system calls.
759 .It Va sysvsem, sysvshm
760 Allow access to SYSV IPC semaphore and shared memory primitives, in the
765 There are pseudo-parameters that are not passed to the kernel, but are
768 to set up the jail environment, often by running specified commands
769 when jails are created or removed.
772 command parameters are
774 command lines that are run in either the system or jail environment.
775 They may be given multiple values, which would run the specified
776 commands in sequence.
777 All commands must succeed (return a zero exit status), or the jail will
778 not be created or removed, as appropriate.
780 The pseudo-parameters are:
781 .Bl -tag -width indent
783 Command(s) to run in the system environment to prepare a jail for creation.
784 These commands are executed before assigning IP addresses and mounting
785 filesystems, so they may be used to create a new jail filesystem if it does
788 Command(s) to run in the system environment before a jail is created.
790 Command(s) to run in the system environment right after a jail has been
791 created, but before commands (or services) get executed in the jail.
793 Command(s) to run in the jail environment when a jail is created.
794 A typical command to run is
799 for use when specifying a jail directly on the command line.
800 Unlike other parameters whose value is a single string,
802 uses the remainder of the
804 command line as its own arguments.
805 .It Va exec.poststart
806 Command(s) to run in the system environment after a jail is created,
809 commands have completed.
811 Command(s) to run in the system environment before a jail is removed.
813 Command(s) to run in the jail environment before a jail is removed,
816 commands have completed.
817 A typical command to run is
818 .Dq sh /etc/rc.shutdown jail .
820 Command(s) to run in the system environment after a jail is removed.
822 Command(s) to run in the system environment after all other actions are done.
823 These commands are executed after unmounting filesystems and removing IP
824 addresses, so they may be used to remove a jail filesystem if it is no longer
827 Run commands in a clean environment.
828 The environment is discarded except for
829 .Ev HOME , SHELL , TERM
835 are set to the target login's default values.
837 is set to the target login.
839 is imported from the current environment.
840 The environment variables from the login class capability database for the
841 target login are also set.
842 .It Va exec.jail_user
843 The user to run commands as, when running in the jail environment.
844 The default is to run the commands as the current user.
845 .It Va exec.system_jail_user
846 This boolean option looks for the
850 file, instead of in the jail's file.
851 .It Va exec.system_user
852 The user to run commands as, when running in the system environment.
853 The default is to run the commands as the current user.
855 The maximum amount of time to wait for a command to complete, in
857 If a command is still running after this timeout has passed,
858 the jail will not be created or removed, as appropriate.
859 .It Va exec.consolelog
860 A file to direct command output (stdout and stderr) to.
862 The FIB (routing table) to set when running commands inside the jail.
864 The maximum amount of time to wait for a jail's processes to exit
867 signal (which happens after the
869 commands have completed).
870 After this many seconds have passed, the jail will be removed, which
871 will kill any remaining processes.
872 If this is set to zero, no
874 is sent and the jail is immediately removed.
875 The default is 10 seconds.
877 A network interface to add the jail's IP addresses
882 An alias for each address will be added to the interface before the
883 jail is created, and will be removed from the interface after the
886 In addition to the IP addresses that are passed to the kernel, an
887 interface, netmask and additional parameters (as supported by
889 may also be specified, in the form
890 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
891 If an interface is given before the IP address, an alias for the address
892 will be added to that interface, as it is with the
895 If a netmask in either dotted-quad or CIDR form is given
896 after an IP address, it will be used when adding the IP alias.
897 If additional parameters are specified then they will also be used when
900 In addition to the IP addresses that are passed to the kernel,
901 an interface, prefix and additional parameters (as supported by
903 may also be specified, in the form
904 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
905 .It Va vnet.interface
906 A network interface to give to a vnet-enabled jail after is it created.
907 The interface will automatically be released when the jail is removed.
911 parameter and add all IP addresses returned by the resolver
912 to the list of addresses
917 This may affect default address selection for outgoing IPv4 connections
919 The address first returned by the resolver for each address family
920 will be used as the primary address.
922 A filesystem to mount before creating the jail (and to unmount after
923 removing it), given as a single
929 format file containing filesystems to mount before creating a jail.
933 filesystem on the chrooted
935 directory, and apply the ruleset in the
937 parameter (or a default of ruleset 4: devfsrules_jail)
938 to restrict the devices visible inside the jail.
942 filesystem on the chrooted
948 filesystem on the chrooted
952 Allow making changes to a
956 Specify a jail (or jails) that this jail depends on.
957 When this jail is to be created, any jail(s) it depends on must already exist.
958 If not, they will be created automatically, up to the completion of the last
960 command, before any action will taken to create this jail.
961 When jails are removed the opposite is true:
962 this jail will be removed, up to the last
964 command, before any jail(s) it depends on are stopped.
967 Jails are typically set up using one of two philosophies: either to
968 constrain a specific application (possibly running with privilege), or
970 .Dq "virtual system image"
971 running a variety of daemons and services.
972 In both cases, a fairly complete file system install of
975 required, so as to provide the necessary command line tools, daemons,
976 libraries, application configuration files, etc.
977 However, for a virtual server configuration, a fair amount of
978 additional work is required so as to replace the
981 This manual page documents the configuration steps necessary to support
982 either of these steps, although the configuration steps may need to be
983 refined based on local requirements.
984 .Ss "Setting up a Jail Directory Tree"
985 To set up a jail directory tree containing an entire
987 distribution, the following
989 command script can be used:
990 .Bd -literal -offset indent
994 make world DESTDIR=$D
995 make distribution DESTDIR=$D
998 In many cases this example would put far more in the jail than needed.
999 In the other extreme case a jail might contain only one file:
1000 the executable to be run in the jail.
1002 We recommend experimentation, and caution that it is a lot easier to
1005 jail and remove things until it stops working,
1006 than it is to start with a
1008 jail and add things until it works.
1009 .Ss "Setting Up a Jail"
1010 Do what was described in
1011 .Sx "Setting Up a Jail Directory Tree"
1012 to build the jail directory tree.
1013 For the sake of this example, we will
1014 assume you built it in
1015 .Pa /data/jail/testjail ,
1018 Substitute below as needed with your
1019 own directory, IP address, and hostname.
1020 .Ss "Setting up the Host Environment"
1021 First, set up the real system's environment to be
1023 For consistency, we will refer to the parent box as the
1024 .Dq "host environment" ,
1025 and to the jailed virtual machine as the
1026 .Dq "jail environment" .
1027 Since jails are implemented using IP aliases, one of the first things to do
1028 is to disable IP services on the host system that listen on all local
1029 IP addresses for a service.
1030 If a network service is present in the host environment that binds all
1031 available IP addresses rather than specific IP addresses, it may service
1032 requests sent to jail IP addresses if the jail did not bind the port.
1035 to only listen on the
1036 appropriate IP address, and so forth.
1037 Add the following to
1039 in the host environment:
1040 .Bd -literal -offset indent
1041 sendmail_enable="NO"
1042 inetd_flags="-wW -a 192.0.2.23"
1047 is the native IP address for the host system, in this example.
1048 Daemons that run out of
1050 can be easily configured to use only the specified host IP address.
1052 will need to be manually configured \(em for some this is possible through
1054 flags entries; for others it is necessary to modify per-application
1055 configuration files, or to recompile the application.
1056 The following frequently deployed services must have their individual
1057 configuration files modified to limit the application to listening
1058 to a specific IP address:
1062 it is necessary to modify
1063 .Pa /etc/ssh/sshd_config .
1067 it is necessary to modify
1068 .Pa /etc/mail/sendmail.cf .
1070 In addition, a number of services must be recompiled in order to run
1071 them in the host environment.
1072 This includes most applications providing services using
1079 In general, applications for which it is not possible to specify which
1080 IP address to bind should not be run in the host environment unless they
1081 should also service requests sent to jail IP addresses.
1083 NFS from the host environment may also cause confusion, and cannot be
1084 easily reconfigured to use only specific IPs, as some NFS services are
1085 hosted directly from the kernel.
1086 Any third-party network software running
1087 in the host environment should also be checked and configured so that it
1088 does not bind all IP addresses, which would result in those services also
1089 appearing to be offered by the jail environments.
1092 these daemons have been disabled or fixed in the host environment, it is
1093 best to reboot so that all daemons are in a known state, to reduce the
1094 potential for confusion later (such as finding that when you send mail
1095 to a jail, and its sendmail is down, the mail is delivered to the host,
1097 .Ss "Configuring the Jail"
1098 Start any jail for the first time without configuring the network
1099 interface so that you can clean it up a little and set up accounts.
1101 with any machine (virtual or not), you will need to set a root password, time
1103 Some of these steps apply only if you intend to run a full virtual server
1104 inside the jail; others apply both for constraining a particular application
1105 or for running a virtual server.
1107 Start a shell in the jail:
1108 .Bd -literal -offset indent
1109 jail -c path=/data/jail/testjail mount.devfs \\
1110 host.hostname=testhostname ip4.addr=192.0.2.100 \\
1114 Assuming no errors, you will end up with a shell prompt within the jail.
1117 and do the post-install configuration to set various configuration options,
1118 or perform these actions manually by editing
1122 .Bl -bullet -offset indent -compact
1125 .Pa /etc/resolv.conf
1126 so that name resolution within the jail will work correctly.
1134 Set a root password, probably different from the real host system.
1138 Add accounts for users in the jail environment.
1140 Install any packages the environment requires.
1143 You may also want to perform any package-specific configuration (web servers,
1144 SSH servers, etc), patch up
1145 .Pa /etc/syslog.conf
1146 so it logs as you would like, etc.
1147 If you are not using a virtual server, you may wish to modify
1149 in the host environment to listen on the syslog socket in the jail
1150 environment; in this example, the syslog socket would be stored in
1151 .Pa /data/jail/testjail/var/run/log .
1153 Exit from the shell, and the jail will be shut down.
1154 .Ss "Starting the Jail"
1155 You are now ready to restart the jail and bring up the environment with
1156 all of its daemons and other programs.
1157 Create an entry for the jail in
1158 .Pa /etc/jail.conf :
1159 .Bd -literal -offset indent
1161 path = /tmp/jail/testjail;
1163 host.hostname = testhostname;
1164 ip4.addr = 192.0.2.100;
1166 exec.start = "/bin/sh /etc/rc";
1167 exec.stop = "/bin/sh /etc/rc.shutdown jail";
1171 To start a virtual server environment,
1173 is run to launch various daemons and services, and
1174 .Pa /etc/rc.shutdown
1175 is run to shut them down when the jail is removed.
1176 If you are running a single application in the jail,
1177 substitute the command used to start the application for
1178 .Dq /bin/sh /etc/rc ;
1179 there may be some script available to cleanly shut down the application,
1180 or it may be sufficient to go without a stop command, and have
1186 Start the jail by running:
1187 .Bd -literal -offset indent
1191 A few warnings may be produced; however, it should all work properly.
1192 You should be able to see
1195 and other processes running within the jail using
1199 flag appearing beside jailed processes.
1200 To see an active list of jails, use
1204 is enabled in the jail environment, you should be able to
1206 to the hostname or IP address of the jailed environment, and log
1207 in using the accounts you created previously.
1209 It is possible to have jails started at boot time.
1214 for more information.
1215 .Ss "Managing the Jail"
1216 Normal machine shutdown commands, such as
1221 cannot be used successfully within the jail.
1222 To kill all processes from within a jail, you may use one of the
1223 following commands, depending on what you want to accomplish:
1224 .Bd -literal -offset indent
1233 signals to all processes in the jail \(em be careful not to run this from
1234 the host environment!
1235 Once all of the jail's processes have died, unless the jail was created
1238 parameter, the jail will be removed.
1240 the intended use of the jail, you may also want to run
1241 .Pa /etc/rc.shutdown
1242 from within the jail.
1244 To shut down the jail from the outside, simply remove it with:
1245 .Bd -literal -offset indent
1249 which will run any commands specified by
1255 to any remaining jailed processes.
1258 .Pa /proc/ Ns Ar pid Ns Pa /status
1259 file contains, as its last field, the name of the jail in which the
1262 to indicate that the process is not running within a jail.
1265 command also shows a
1267 flag for processes in a jail.
1269 You can also list/kill processes based on their jail ID.
1270 To show processes and their jail ID, use the following command:
1272 .Dl "ps ax -o pid,jid,args"
1274 To show and then kill processes in jail number 3 use the following commands:
1275 .Bd -literal -offset indent
1282 .Ss "Jails and File Systems"
1283 It is not possible to
1287 any file system inside a jail unless the file system is marked
1288 jail-friendly, the jail's
1290 parameter is set, and the jail's
1292 parameter is lower than 2.
1294 Multiple jails sharing the same file system can influence each other.
1295 For example, a user in one jail can fill the file system,
1296 leaving no space for processes in the other jail.
1299 to prevent this will not work either, as the file system quotas
1300 are not aware of jails but only look at the user and group IDs.
1301 This means the same user ID in two jails share a single file
1303 One would need to use one file system per jail to make this work.
1304 .Ss "Sysctl MIB Entries"
1306 .Va security.jail.jailed
1307 can be used to determine if a process is running inside a jail (value
1308 is one) or not (value is zero).
1311 .Va security.jail.jail_max_af_ips
1312 determines how may address per address family a jail may have.
1315 Some MIB variables have per-jail settings.
1316 Changes to these variables by a jailed process do not affect the host
1317 environment, only the jail environment.
1319 .Va kern.securelevel ,
1320 .Va security.bsd.suser_enabled ,
1322 .Va kern.domainname ,
1326 .Ss "Hierarchical Jails"
1329 parameter, processes within a jail may be able to create jails of their own.
1330 These child jails are kept in a hierarchy, with jails only able to see and/or
1331 modify the jails they created (or those jails' children).
1332 Each jail has a read-only
1334 parameter, containing the
1336 of the jail that created it; a
1338 of 0 indicates the jail is a child of the current jail (or is a top-level
1339 jail if the current process isn't jailed).
1341 Jailed processes are not allowed to confer greater permissions than they
1342 themselves are given, e.g., if a jail is created with
1344 it is not able to create a jail with
1347 Similarly, such restrictions as
1351 may not be bypassed in child jails.
1353 A child jail may in turn create its own child jails if its own
1355 parameter is set (remember it is zero by default).
1356 These jails are visible to and can be modified by their parent and all
1359 Jail names reflect this hierarchy, with a full name being an MIB-type string
1361 For example, if a base system process creates a jail
1363 and a process under that jail creates another jail
1365 then the second jail will be seen as
1367 in the base system (though it is only seen as
1369 to any processes inside jail
1371 Jids on the other hand exist in a single space, and each jail must have a
1374 Like the names, a child jail's
1376 appears relative to its creator's own
1378 This is by virtue of the child jail being created in the chrooted
1379 environment of the first jail.
1421 Hierarchical/extensible jails were introduced in
1423 The configuration file was introduced in
1427 The jail feature was written by
1428 .An Poul-Henning Kamp
1430 who contributed it to
1434 wrote the extended documentation, found a few bugs, added
1435 a few new features, and cleaned up the userland jail environment.
1438 added multi-IP jail support for IPv4 and IPv6 based on a patch
1440 .An Pawel Jakub Dawidek
1444 added the extensible jail parameters, hierarchical jails,
1445 and the configuration file.
1447 It might be a good idea to add an
1448 address alias flag such that daemons listening on all IPs
1450 will not bind on that address, which would facilitate building a safe
1451 host environment such that host daemons do not impose on services offered
1453 Currently, the simplest answer is to minimize services
1454 offered on the host, possibly limiting it to services offered from
1456 which is easily configurable.
1458 Great care should be taken when managing directories visible within the jail.
1459 For example, if a jailed process has its current working directory set to a
1460 directory that is moved out of the jail's chroot, then the process may gain
1461 access to the file space outside of the jail.
1462 It is recommended that directories always be copied, rather than moved, out
1465 In addition, there are several ways in which an unprivileged user
1466 outside the jail can cooperate with a privileged user inside the jail
1467 and thereby obtain elevated privileges in the host environment.
1468 Most of these attacks can be mitigated by ensuring that the jail root
1469 is not accessible to unprivileged users in the host environment.
1470 Regardless, as a general rule, untrusted users with privileged access
1471 to a jail should not be given access to the host environment.