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2 .\" Copyright (c) 2008-2012 James Gritton
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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
587 .It Va allow.reserved_ports
588 The jail root may bind to ports lower than 1024.
589 .It Va allow.unprivileged_proc_debug
590 Unprivileged processes in the jail may use debugging facilities.
592 The value of the jail's
593 .Va security.bsd.suser_enabled
595 The super-user will be disabled automatically if its parent system has it
597 The super-user is enabled by default.
601 Kernel modules may add their own parameters, which only exist when the
603 These are typically headed under a parameter named after the module,
606 to give the jail full use of the module,
608 to encapsulate the jail in some module-specific way,
611 to make the module unavailable to the jail.
612 There also may be other parameters to define jail behavior within the module.
613 Module-specific parameters include:
614 .Bl -tag -width indent
615 .It Va allow.mount.fdescfs
616 privileged users inside the jail will be able to mount and unmount the
618 This permission is effective only together with
622 is set to a value lower than 2.
623 .It Va allow.mount.fusefs
624 privileged users inside the jail will be able to mount and unmount
625 fuse-based file systems.
626 This permission is effective only together with
630 is set to a value lower than 2.
631 .It Va allow.mount.nullfs
632 privileged users inside the jail will be able to mount and unmount the
634 This permission is effective only together with
638 is set to a value lower than 2.
639 .It Va allow.mount.procfs
640 privileged users inside the jail will be able to mount and unmount the
642 This permission is effective only together with
646 is set to a value lower than 2.
647 .It Va allow.mount.linprocfs
648 privileged users inside the jail will be able to mount and unmount the
649 linprocfs file system.
650 This permission is effective only together with
654 is set to a value lower than 2.
655 .It Va allow.mount.linsysfs
656 privileged users inside the jail will be able to mount and unmount the
657 linsysfs file system.
658 This permission is effective only together with
662 is set to a value lower than 2.
663 .It Va allow.mount.tmpfs
664 privileged users inside the jail will be able to mount and unmount the
666 This permission is effective only together with
670 is set to a value lower than 2.
671 .It Va allow.mount.zfs
672 privileged users inside the jail will be able to mount and unmount the
674 This permission is effective only together with
678 is set to a value lower than 2.
681 for information on how to configure the ZFS filesystem to operate from
686 This flag is only available when the
688 kernel module is loaded.
690 Determine how a jail's Linux emulation environment appears.
693 will keep the same environment, and
695 will give the jail its own environment (still originally inherited when
696 the jail is created).
697 .It Va linux.osname , linux.osrelease , linux.oss_version
698 The Linux OS name, OS release, and OSS version associated with this jail.
700 Allow access to SYSV IPC message primitives.
703 all IPC objects on the system are visible to this jail, whether they
704 were created by the jail itself, the base system, or other jails.
707 the jail will have its own key namespace, and can only see the objects
709 the system (or parent jail) has access to the jail's objects, but not to
713 the jail cannot perform any sysvmsg-related system calls.
714 .It Va sysvsem, sysvshm
715 Allow access to SYSV IPC semaphore and shared memory primitives, in the
720 There are pseudo-parameters that are not passed to the kernel, but are
723 to set up the jail environment, often by running specified commands
724 when jails are created or removed.
727 command parameters are
729 command lines that are run in either the system or jail environment.
730 They may be given multiple values, which would run the specified
731 commands in sequence.
732 All commands must succeed (return a zero exit status), or the jail will
733 not be created or removed, as appropriate.
735 The pseudo-parameters are:
736 .Bl -tag -width indent
738 Command(s) to run in the system environment to prepare a jail for creation.
739 These commands are executed before assigning IP addresses and mounting
740 filesystems, so they may be used to create a new jail filesystem if it does
743 Command(s) to run in the system environment before a jail is created.
745 Command(s) to run in the system environment right after a jail has been
746 created, but before commands (or services) get executed in the jail.
748 Command(s) to run in the jail environment when a jail is created.
749 A typical command to run is
754 for use when specifying a jail directly on the command line.
755 Unlike other parameters whose value is a single string,
757 uses the remainder of the
759 command line as its own arguments.
760 .It Va exec.poststart
761 Command(s) to run in the system environment after a jail is created,
764 commands have completed.
766 Command(s) to run in the system environment before a jail is removed.
768 Command(s) to run in the jail environment before a jail is removed,
771 commands have completed.
772 A typical command to run is
773 .Dq sh /etc/rc.shutdown jail .
775 Command(s) to run in the system environment after a jail is removed.
777 Command(s) to run in the system environment after all other actions are done.
778 These commands are executed after unmounting filesystems and removing IP
779 addresses, so they may be used to remove a jail filesystem if it is no longer
782 Run commands in a clean environment.
783 The environment is discarded except for
784 .Ev HOME , SHELL , TERM
790 are set to the target login's default values.
792 is set to the target login.
794 is imported from the current environment.
795 The environment variables from the login class capability database for the
796 target login are also set.
797 .It Va exec.jail_user
798 The user to run commands as, when running in the jail environment.
799 The default is to run the commands as the current user.
800 .It Va exec.system_jail_user
801 This boolean option looks for the
805 file, instead of in the jail's file.
806 .It Va exec.system_user
807 The user to run commands as, when running in the system environment.
808 The default is to run the commands as the current user.
810 The maximum amount of time to wait for a command to complete, in
812 If a command is still running after this timeout has passed,
813 the jail will not be created or removed, as appropriate.
814 .It Va exec.consolelog
815 A file to direct command output (stdout and stderr) to.
817 The FIB (routing table) to set when running commands inside the jail.
819 The maximum amount of time to wait for a jail's processes to exit
822 signal (which happens after the
824 commands have completed).
825 After this many seconds have passed, the jail will be removed, which
826 will kill any remaining processes.
827 If this is set to zero, no
829 is sent and the jail is immediately removed.
830 The default is 10 seconds.
832 A network interface to add the jail's IP addresses
837 An alias for each address will be added to the interface before the
838 jail is created, and will be removed from the interface after the
841 In addition to the IP addresses that are passed to the kernel, an
842 interface, netmask and additional parameters (as supported by
844 may also be specified, in the form
845 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
846 If an interface is given before the IP address, an alias for the address
847 will be added to that interface, as it is with the
850 If a netmask in either dotted-quad or CIDR form is given
851 after an IP address, it will be used when adding the IP alias.
852 If additional parameters are specified then they will also be used when
855 In addition to the IP addresses that are passed to the kernel,
856 an interface, prefix and additional parameters (as supported by
858 may also be specified, in the form
859 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
860 .It Va vnet.interface
861 A network interface to give to a vnet-enabled jail after is it created.
862 The interface will automatically be released when the jail is removed.
866 parameter and add all IP addresses returned by the resolver
867 to the list of addresses
872 This may affect default address selection for outgoing IPv4 connections
874 The address first returned by the resolver for each address family
875 will be used as the primary address.
877 A filesystem to mount before creating the jail (and to unmount after
878 removing it), given as a single
884 format file containing filesystems to mount before creating a jail.
888 filesystem on the chrooted
890 directory, and apply the ruleset in the
892 parameter (or a default of ruleset 4: devfsrules_jail)
893 to restrict the devices visible inside the jail.
897 filesystem on the chrooted
903 filesystem on the chrooted
907 Allow making changes to a
911 Specify a jail (or jails) that this jail depends on.
912 When this jail is to be created, any jail(s) it depends on must already exist.
913 If not, they will be created automatically, up to the completion of the last
915 command, before any action will taken to create this jail.
916 When jails are removed the opposite is true:
917 this jail will be removed, up to the last
919 command, before any jail(s) it depends on are stopped.
922 Jails are typically set up using one of two philosophies: either to
923 constrain a specific application (possibly running with privilege), or
925 .Dq "virtual system image"
926 running a variety of daemons and services.
927 In both cases, a fairly complete file system install of
930 required, so as to provide the necessary command line tools, daemons,
931 libraries, application configuration files, etc.
932 However, for a virtual server configuration, a fair amount of
933 additional work is required so as to replace the
936 This manual page documents the configuration steps necessary to support
937 either of these steps, although the configuration steps may need to be
938 refined based on local requirements.
939 .Ss "Setting up a Jail Directory Tree"
940 To set up a jail directory tree containing an entire
942 distribution, the following
944 command script can be used:
945 .Bd -literal -offset indent
949 make world DESTDIR=$D
950 make distribution DESTDIR=$D
953 In many cases this example would put far more in the jail than needed.
954 In the other extreme case a jail might contain only one file:
955 the executable to be run in the jail.
957 We recommend experimentation, and caution that it is a lot easier to
960 jail and remove things until it stops working,
961 than it is to start with a
963 jail and add things until it works.
964 .Ss "Setting Up a Jail"
965 Do what was described in
966 .Sx "Setting Up a Jail Directory Tree"
967 to build the jail directory tree.
968 For the sake of this example, we will
969 assume you built it in
970 .Pa /data/jail/testjail ,
973 Substitute below as needed with your
974 own directory, IP address, and hostname.
975 .Ss "Setting up the Host Environment"
976 First, set up the real system's environment to be
978 For consistency, we will refer to the parent box as the
979 .Dq "host environment" ,
980 and to the jailed virtual machine as the
981 .Dq "jail environment" .
982 Since jails are implemented using IP aliases, one of the first things to do
983 is to disable IP services on the host system that listen on all local
984 IP addresses for a service.
985 If a network service is present in the host environment that binds all
986 available IP addresses rather than specific IP addresses, it may service
987 requests sent to jail IP addresses if the jail did not bind the port.
990 to only listen on the
991 appropriate IP address, and so forth.
994 in the host environment:
995 .Bd -literal -offset indent
997 inetd_flags="-wW -a 192.0.2.23"
1002 is the native IP address for the host system, in this example.
1003 Daemons that run out of
1005 can be easily configured to use only the specified host IP address.
1007 will need to be manually configured \(em for some this is possible through
1009 flags entries; for others it is necessary to modify per-application
1010 configuration files, or to recompile the application.
1011 The following frequently deployed services must have their individual
1012 configuration files modified to limit the application to listening
1013 to a specific IP address:
1017 it is necessary to modify
1018 .Pa /etc/ssh/sshd_config .
1022 it is necessary to modify
1023 .Pa /etc/mail/sendmail.cf .
1025 In addition, a number of services must be recompiled in order to run
1026 them in the host environment.
1027 This includes most applications providing services using
1034 In general, applications for which it is not possible to specify which
1035 IP address to bind should not be run in the host environment unless they
1036 should also service requests sent to jail IP addresses.
1038 NFS from the host environment may also cause confusion, and cannot be
1039 easily reconfigured to use only specific IPs, as some NFS services are
1040 hosted directly from the kernel.
1041 Any third-party network software running
1042 in the host environment should also be checked and configured so that it
1043 does not bind all IP addresses, which would result in those services also
1044 appearing to be offered by the jail environments.
1047 these daemons have been disabled or fixed in the host environment, it is
1048 best to reboot so that all daemons are in a known state, to reduce the
1049 potential for confusion later (such as finding that when you send mail
1050 to a jail, and its sendmail is down, the mail is delivered to the host,
1052 .Ss "Configuring the Jail"
1053 Start any jail for the first time without configuring the network
1054 interface so that you can clean it up a little and set up accounts.
1056 with any machine (virtual or not), you will need to set a root password, time
1058 Some of these steps apply only if you intend to run a full virtual server
1059 inside the jail; others apply both for constraining a particular application
1060 or for running a virtual server.
1062 Start a shell in the jail:
1063 .Bd -literal -offset indent
1064 jail -c path=/data/jail/testjail mount.devfs \\
1065 host.hostname=testhostname ip4.addr=192.0.2.100 \\
1069 Assuming no errors, you will end up with a shell prompt within the jail.
1072 and do the post-install configuration to set various configuration options,
1073 or perform these actions manually by editing
1077 .Bl -bullet -offset indent -compact
1080 .Pa /etc/resolv.conf
1081 so that name resolution within the jail will work correctly.
1089 Set a root password, probably different from the real host system.
1093 Add accounts for users in the jail environment.
1095 Install any packages the environment requires.
1098 You may also want to perform any package-specific configuration (web servers,
1099 SSH servers, etc), patch up
1100 .Pa /etc/syslog.conf
1101 so it logs as you would like, etc.
1102 If you are not using a virtual server, you may wish to modify
1104 in the host environment to listen on the syslog socket in the jail
1105 environment; in this example, the syslog socket would be stored in
1106 .Pa /data/jail/testjail/var/run/log .
1108 Exit from the shell, and the jail will be shut down.
1109 .Ss "Starting the Jail"
1110 You are now ready to restart the jail and bring up the environment with
1111 all of its daemons and other programs.
1112 Create an entry for the jail in
1113 .Pa /etc/jail.conf :
1114 .Bd -literal -offset indent
1116 path = /tmp/jail/testjail;
1118 host.hostname = testhostname;
1119 ip4.addr = 192.0.2.100;
1121 exec.start = "/bin/sh /etc/rc";
1122 exec.stop = "/bin/sh /etc/rc.shutdown jail";
1126 To start a virtual server environment,
1128 is run to launch various daemons and services, and
1129 .Pa /etc/rc.shutdown
1130 is run to shut them down when the jail is removed.
1131 If you are running a single application in the jail,
1132 substitute the command used to start the application for
1133 .Dq /bin/sh /etc/rc ;
1134 there may be some script available to cleanly shut down the application,
1135 or it may be sufficient to go without a stop command, and have
1141 Start the jail by running:
1142 .Bd -literal -offset indent
1146 A few warnings may be produced; however, it should all work properly.
1147 You should be able to see
1150 and other processes running within the jail using
1154 flag appearing beside jailed processes.
1155 To see an active list of jails, use
1159 is enabled in the jail environment, you should be able to
1161 to the hostname or IP address of the jailed environment, and log
1162 in using the accounts you created previously.
1164 It is possible to have jails started at boot time.
1169 for more information.
1170 .Ss "Managing the Jail"
1171 Normal machine shutdown commands, such as
1176 cannot be used successfully within the jail.
1177 To kill all processes from within a jail, you may use one of the
1178 following commands, depending on what you want to accomplish:
1179 .Bd -literal -offset indent
1188 signals to all processes in the jail \(em be careful not to run this from
1189 the host environment!
1190 Once all of the jail's processes have died, unless the jail was created
1193 parameter, the jail will be removed.
1195 the intended use of the jail, you may also want to run
1196 .Pa /etc/rc.shutdown
1197 from within the jail.
1199 To shut down the jail from the outside, simply remove it with:
1200 .Bd -literal -offset indent
1204 which will run any commands specified by
1210 to any remaining jailed processes.
1213 .Pa /proc/ Ns Ar pid Ns Pa /status
1214 file contains, as its last field, the name of the jail in which the
1217 to indicate that the process is not running within a jail.
1220 command also shows a
1222 flag for processes in a jail.
1224 You can also list/kill processes based on their jail ID.
1225 To show processes and their jail ID, use the following command:
1227 .Dl "ps ax -o pid,jid,args"
1229 To show and then kill processes in jail number 3 use the following commands:
1230 .Bd -literal -offset indent
1237 .Ss "Jails and File Systems"
1238 It is not possible to
1242 any file system inside a jail unless the file system is marked
1243 jail-friendly, the jail's
1245 parameter is set, and the jail's
1247 parameter is lower than 2.
1249 Multiple jails sharing the same file system can influence each other.
1250 For example, a user in one jail can fill the file system,
1251 leaving no space for processes in the other jail.
1254 to prevent this will not work either, as the file system quotas
1255 are not aware of jails but only look at the user and group IDs.
1256 This means the same user ID in two jails share a single file
1258 One would need to use one file system per jail to make this work.
1259 .Ss "Sysctl MIB Entries"
1261 .Va security.jail.jailed
1262 can be used to determine if a process is running inside a jail (value
1263 is one) or not (value is zero).
1266 .Va security.jail.max_af_ips
1267 determines how may address per address family a jail may have.
1270 Some MIB variables have per-jail settings.
1271 Changes to these variables by a jailed process do not affect the host
1272 environment, only the jail environment.
1274 .Va kern.securelevel ,
1275 .Va security.bsd.suser_enabled ,
1277 .Va kern.domainname ,
1281 .Ss "Hierarchical Jails"
1284 parameter, processes within a jail may be able to create jails of their own.
1285 These child jails are kept in a hierarchy, with jails only able to see and/or
1286 modify the jails they created (or those jails' children).
1287 Each jail has a read-only
1289 parameter, containing the
1291 of the jail that created it; a
1293 of 0 indicates the jail is a child of the current jail (or is a top-level
1294 jail if the current process isn't jailed).
1296 Jailed processes are not allowed to confer greater permissions than they
1297 themselves are given, e.g., if a jail is created with
1299 it is not able to create a jail with
1302 Similarly, such restrictions as
1306 may not be bypassed in child jails.
1308 A child jail may in turn create its own child jails if its own
1310 parameter is set (remember it is zero by default).
1311 These jails are visible to and can be modified by their parent and all
1314 Jail names reflect this hierarchy, with a full name being an MIB-type string
1316 For example, if a base system process creates a jail
1318 and a process under that jail creates another jail
1320 then the second jail will be seen as
1322 in the base system (though it is only seen as
1324 to any processes inside jail
1326 Jids on the other hand exist in a single space, and each jail must have a
1329 Like the names, a child jail's
1331 appears relative to its creator's own
1333 This is by virtue of the child jail being created in the chrooted
1334 environment of the first jail.
1374 Hierarchical/extensible jails were introduced in
1376 The configuration file was introduced in
1380 The jail feature was written by
1381 .An Poul-Henning Kamp
1383 who contributed it to
1387 wrote the extended documentation, found a few bugs, added
1388 a few new features, and cleaned up the userland jail environment.
1391 added multi-IP jail support for IPv4 and IPv6 based on a patch
1393 .An Pawel Jakub Dawidek
1397 added the extensible jail parameters, hierarchical jails,
1398 and the configuration file.
1400 It might be a good idea to add an
1401 address alias flag such that daemons listening on all IPs
1403 will not bind on that address, which would facilitate building a safe
1404 host environment such that host daemons do not impose on services offered
1406 Currently, the simplest answer is to minimize services
1407 offered on the host, possibly limiting it to services offered from
1409 which is easily configurable.
1411 Great care should be taken when managing directories visible within the jail.
1412 For example, if a jailed process has its current working directory set to a
1413 directory that is moved out of the jail's chroot, then the process may gain
1414 access to the file space outside of the jail.
1415 It is recommended that directories always be copied, rather than moved, out
1418 In addition, there are several ways in which an unprivileged user
1419 outside the jail can cooperate with a privileged user inside the jail
1420 and thereby obtain elevated privileges in the host environment.
1421 Most of these attacks can be mitigated by ensuring that the jail root
1422 is not accessible to unprivileged users in the host environment.
1423 Regardless, as a general rule, untrusted users with privileged access
1424 to a jail should not be given access to the host environment.