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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 .Op Ar path hostname [ Ar ip Ns [ Ns Ar ,... Ns ]] Ar command ...
69 utility creates new jails, or modifies or removes existing jails.
70 It can also print a list of configured jails and their parameters.
73 is specified via parameters on the command line, or in the
77 At least one of the options
84 These options are used alone or in combination to describe the operation to
86 .Bl -tag -width indent
93 parameters (if specified on the command line)
94 must not refer to an existing jail.
96 Exhibit a list of all configured non-wildcard jails and their parameters.
97 No jail creation, modification or removal performed if this option is used.
100 string is used to separate parameters.
103 utility to list running jails.
105 Modify an existing jail.
110 parameters must exist and refer to an existing jail.
111 Some parameters may not be changed on a running jail.
115 specified by jid or name.
116 All jailed processes are killed, and all jails that are
117 children of this jail are also
120 Restart an existing jail.
121 The jail is first removed and then re-created, as if
125 were run in succession.
127 Create a jail if it does not exist, or modify the jail if it does exist.
129 Modify an existing jail.
130 The jail may be restarted if necessary to modify parameters than could
131 not otherwise be changed.
133 Create a jail if it doesn't exist, or modify (and possibly restart) the
134 jail if it does exist.
137 Other available options are:
138 .Bl -tag -width indent
140 Allow making changes to a dying jail, equivalent to the
143 .It Fl f Ar conf_file
144 Use configuration file
146 instead of the default
153 and add all IP addresses returned by the resolver
154 to the list of addresses for this jail.
155 This is equivalent to the
159 Output (only) the jail identifier of the newly created jail(s).
166 file, containing the parameters used to start the jail.
168 Run commands in a clean environment.
169 This is deprecated and is equivalent to the exec.clean parameter.
172 This is deprecated and is equivalent to the
176 Limit the number of commands from
178 that can run simultaneously.
180 Suppress the message printed whenever a jail is created, modified or removed.
181 Only error messages will be printed.
185 option that removes an existing jail without using the configuration file.
186 No removal-related parameters for this jail will be used \(em the jail will
188 .It Fl s Ar securelevel
191 MIB entry to the specified value inside the newly created jail.
192 This is deprecated and is equivalent to the
196 The user name from host environment as whom jailed commands should run.
197 This is deprecated and is equivalent to the
200 .Va exec.system_jail_user
203 The user name from the jailed environment as whom jailed commands should run.
204 This is deprecated and is equivalent to the
208 Print a message on every operation, such as running commands and
209 mounting filesystems.
212 If no arguments are given after the options, the operation (except
213 remove) will be performed on all jails specified in the
216 A single argument of a jail name will operate only on the specified jail.
221 options can also remove running jails that aren't in the
223 file, specified by name or jid.
227 is a wildcard that will operate on all jails, regardless of whether
230 this is the surest way for
233 If hierarchical jails exist, a partial-matching wildcard definition may
235 For example, an argument of
237 would apply to jails with names like
242 A jail may be specified with parameters directly on the command line.
245 file will not be used.
246 For backward compatibility, the command line may also have four fixed
247 parameters, without names:
253 This mode will always create a new jail, and the
257 options do not apply (and must not be present).
261 file, or on the command line, are generally of the form
263 Some parameters are boolean, and do not have a value but are set by the
264 name alone with or without a
270 They can also be given the values
274 Other parameters may have more than one value, specified as a
275 comma-separated list or with
277 in the configuration file (see
283 utility recognizes two classes of parameters.
284 There are the true jail
285 parameters that are passed to the kernel when the jail is created,
286 which can be seen with
288 and can (usually) be changed with
290 Then there are pseudo-parameters that are only used by
294 Jails have a set of core parameters, and kernel modules can add their own
296 The current set of available parameters can be retrieved via
297 .Dq Nm sysctl Fl d Va security.jail.param .
298 Any parameters not set will be given default values, often based on the
300 The core parameters are:
301 .Bl -tag -width indent
304 This will be assigned automatically to a new jail (or can be explicitly
305 set), and can be used to identify the jail for later modification, or
312 This is an arbitrary string that identifies a jail (except it may not
317 it can be passed to later
325 is supplied, a default is assumed that is the same as the
329 parameter is implied by the
331 file format, and need not be explicitly set when using the configuration
334 The directory which is to be the root of the jail.
335 Any commands run inside the jail, either by
339 are run from this directory.
341 A list of IPv4 addresses assigned to the jail.
342 If this is set, the jail is restricted to using only these addresses.
343 Any attempts to use other addresses fail, and attempts to use wildcard
344 addresses silently use the jailed address instead.
345 For IPv4 the first address given will be used as the source address
346 when source address selection on unbound sockets cannot find a better
348 It is only possible to start multiple jails with the same IP address
349 if none of the jails has more than this single overlapping IP address
352 A boolean option to change the formerly mentioned behaviour and disable
353 IPv4 source address selection for the jail in favour of the primary
354 IPv4 address of the jail.
355 Source address selection is enabled by default for all jails and the
357 setting of a parent jail is not inherited for any child jails.
359 Control the availability of IPv4 addresses.
362 to allow unrestricted access to all system addresses,
364 to restrict addresses via
368 to stop the jail from using IPv4 entirely.
371 parameter implies a value of
373 .It Va ip6.addr , Va ip6.saddrsel , Va ip6
374 A set of IPv6 options for the jail, the counterparts to
381 Create the jail with its own virtual network stack,
382 with its own network interfaces, addresses, routing table, etc.
383 The kernel must have been compiled with the
385 for this to be available.
388 to use the system network stack, possibly with restricted IP addresses,
391 to create a new network stack.
393 The hostname of the jail.
394 Other similar parameters are
395 .Va host.domainname ,
400 Set the origin of hostname and related information.
403 to use the system information and
405 for the jail to use the information from the above fields.
406 Setting any of the above fields implies a value of
409 The value of the jail's
412 A jail never has a lower securelevel than its parent system, but by
413 setting this parameter it may have a higher one.
414 If the system securelevel is changed, any jail securelevels will be at
417 The number of the devfs ruleset that is enforced for mounting devfs in
419 A value of zero (default) means no ruleset is enforced.
420 Descendant jails inherit the parent jail's devfs ruleset enforcement.
421 Mounting devfs inside a jail is possible only if the
424 .Va allow.mount.devfs
425 permissions are effective and
427 is set to a value lower than 2.
428 Devfs rules and rulesets cannot be viewed or modified from inside a jail.
430 NOTE: It is important that only appropriate device nodes in devfs be
431 exposed to a jail; access to disk devices in the jail may permit processes
432 in the jail to bypass the jail sandboxing by modifying files outside of
436 for information on how to use devfs rules to limit access to entries
437 in the per-jail devfs.
438 A simple devfs ruleset for jails is available as ruleset #4 in
439 .Pa /etc/defaults/devfs.rules .
441 The number of child jails allowed to be created by this jail (or by
442 other jails under this jail).
443 This limit is zero by default, indicating the jail is not allowed to
446 .Sx "Hierarchical Jails"
447 section for more information.
449 The number of descendants of this jail, including its own child jails
450 and any jails created under them.
451 .It Va enforce_statfs
452 This determines what information processes in a jail are able to get
454 It affects the behaviour of the following syscalls:
460 (as well as similar compatibility syscalls).
461 When set to 0, all mount points are available without any restrictions.
462 When set to 1, only mount points below the jail's chroot directory are
464 In addition to that, the path to the jail's chroot directory is removed
465 from the front of their pathnames.
466 When set to 2 (default), above syscalls can operate only on a mount-point
467 where the jail's chroot directory is located.
469 Setting this boolean parameter allows a jail to exist without any
471 Normally, a command is run as part of jail creation, and then the jail
472 is destroyed as its last process exits.
473 A new jail must have either the
479 pseudo-parameter set.
481 The ID of the cpuset associated with this jail (read-only).
483 This is true if the jail is in the process of shutting down (read-only).
487 of the parent of this jail, or zero if this is a top-level jail
490 The string for the jail's
494 The number for the jail's
498 Some restrictions of the jail environment may be set on a per-jail
500 With the exception of
501 .Va allow.set_hostname
503 .Va allow.reserved_ports ,
504 these boolean parameters are off by default.
505 .Bl -tag -width indent
506 .It Va allow.set_hostname
507 The jail's hostname may be changed via
512 A process within the jail has access to System V IPC primitives.
513 This is deprecated in favor of the per-module parameters (see below).
514 When this parameter is set, it is equivalent to setting
521 .It Va allow.raw_sockets
522 The jail root is allowed to create raw sockets.
523 Setting this parameter allows utilities like
527 to operate inside the jail.
528 If this is set, the source IP addresses are enforced to comply
529 with the IP address bound to the jail, regardless of whether or not
532 flag has been set on the socket.
533 Since raw sockets can be used to configure and interact with various
534 network subsystems, extra caution should be used where privileged access
535 to jails is given out to untrusted parties.
537 Normally, privileged users inside a jail are treated as unprivileged by
539 When this parameter is set, such users are treated as privileged, and
540 may manipulate system file flags subject to the usual constraints on
541 .Va kern.securelevel .
543 privileged users inside the jail will be able to mount and unmount file
544 system types marked as jail-friendly.
547 command can be used to find file system types available for mount from
549 This permission is effective only if
551 is set to a value lower than 2.
552 .It Va allow.mount.devfs
553 privileged users inside the jail will be able to mount and unmount the
555 This permission is effective only together with
559 is set to a value lower than 2.
560 The devfs ruleset should be restricted from the default by using the
564 The jail root may administer quotas on the jail's filesystem(s).
565 This includes filesystems that the jail may share with other jails or
566 with non-jailed parts of the system.
567 .It Va allow.read_msgbuf
568 Jailed users may read the kernel message buffer.
570 .Va security.bsd.unprivileged_read_msgbuf
571 MIB entry is zero, this will be restricted to the root user.
572 .It Va allow.socket_af
573 Sockets within a jail are normally restricted to IPv4, IPv6, local
574 (UNIX), and route. This allows access to other protocol stacks that
575 have not had jail functionality added to them.
577 Locking or unlocking physical pages in memory are normally not available
579 When this parameter is set, users may
584 .Va security.bsd.unprivileged_mlock
586 .It Va allow.reserved_ports
587 The jail root may bind to ports lower than 1024.
588 .It Va allow.unprivileged_proc_debug
589 Unprivileged processes in the jail may use debugging facilities.
591 The value of the jail's
592 .Va security.bsd.suser_enabled
594 The super-user will be disabled automatically if its parent system has it
596 The super-user is enabled by default.
600 Kernel modules may add their own parameters, which only exist when the
602 These are typically headed under a parameter named after the module,
605 to give the jail full use of the module,
607 to encapsulate the jail in some module-specific way,
610 to make the module unavailable to the jail.
611 There also may be other parameters to define jail behavior within the module.
612 Module-specific parameters include:
613 .Bl -tag -width indent
614 .It Va allow.mount.fdescfs
615 privileged users inside the jail will be able to mount and unmount the
617 This permission is effective only together with
621 is set to a value lower than 2.
622 .It Va allow.mount.fusefs
623 privileged users inside the jail will be able to mount and unmount
624 fuse-based file systems.
625 This permission is effective only together with
629 is set to a value lower than 2.
630 .It Va allow.mount.nullfs
631 privileged users inside the jail will be able to mount and unmount the
633 This permission is effective only together with
637 is set to a value lower than 2.
638 .It Va allow.mount.procfs
639 privileged users inside the jail will be able to mount and unmount the
641 This permission is effective only together with
645 is set to a value lower than 2.
646 .It Va allow.mount.linprocfs
647 privileged users inside the jail will be able to mount and unmount the
648 linprocfs file system.
649 This permission is effective only together with
653 is set to a value lower than 2.
654 .It Va allow.mount.linsysfs
655 privileged users inside the jail will be able to mount and unmount the
656 linsysfs file system.
657 This permission is effective only together with
661 is set to a value lower than 2.
662 .It Va allow.mount.tmpfs
663 privileged users inside the jail will be able to mount and unmount the
665 This permission is effective only together with
669 is set to a value lower than 2.
670 .It Va allow.mount.zfs
671 privileged users inside the jail will be able to mount and unmount the
673 This permission is effective only together with
677 is set to a value lower than 2.
680 for information on how to configure the ZFS filesystem to operate from
685 This flag is only available when the
687 kernel module is loaded.
689 Determine how a jail's Linux emulation environment appears.
692 will keep the same environment, and
694 will give the jail its own environment (still originally inherited when
695 the jail is created).
696 .It Va linux.osname , linux.osrelease , linux.oss_version
697 The Linux OS name, OS release, and OSS version associated with this jail.
699 Allow access to SYSV IPC message primitives.
702 all IPC objects on the system are visible to this jail, whether they
703 were created by the jail itself, the base system, or other jails.
706 the jail will have its own key namespace, and can only see the objects
708 the system (or parent jail) has access to the jail's objects, but not to
712 the jail cannot perform any sysvmsg-related system calls.
713 .It Va sysvsem, sysvshm
714 Allow access to SYSV IPC semaphore and shared memory primitives, in the
719 There are pseudo-parameters that are not passed to the kernel, but are
722 to set up the jail environment, often by running specified commands
723 when jails are created or removed.
726 command parameters are
728 command lines that are run in either the system or jail environment.
729 They may be given multiple values, which would run the specified
730 commands in sequence.
731 All commands must succeed (return a zero exit status), or the jail will
732 not be created or removed, as appropriate.
734 The pseudo-parameters are:
735 .Bl -tag -width indent
737 Command(s) to run in the system environment to prepare a jail for creation.
738 These commands are executed before assigning IP addresses and mounting
739 filesystems, so they may be used to create a new jail filesystem if it does
742 Command(s) to run in the system environment before a jail is created.
744 Command(s) to run in the system environment right after a jail has been
745 created, but before commands (or services) get executed in the jail.
747 Command(s) to run in the jail environment when a jail is created.
748 A typical command to run is
753 for use when specifying a jail directly on the command line.
754 Unlike other parameters whose value is a single string,
756 uses the remainder of the
758 command line as its own arguments.
759 .It Va exec.poststart
760 Command(s) to run in the system environment after a jail is created,
763 commands have completed.
765 Command(s) to run in the system environment before a jail is removed.
767 Command(s) to run in the jail environment before a jail is removed,
770 commands have completed.
771 A typical command to run is
772 .Dq sh /etc/rc.shutdown jail .
774 Command(s) to run in the system environment after a jail is removed.
776 Command(s) to run in the system environment after all other actions are done.
777 These commands are executed after unmounting filesystems and removing IP
778 addresses, so they may be used to remove a jail filesystem if it is no longer
781 Run commands in a clean environment.
782 The environment is discarded except for
783 .Ev HOME , SHELL , TERM
789 are set to the target login's default values.
791 is set to the target login.
793 is imported from the current environment.
794 The environment variables from the login class capability database for the
795 target login are also set.
796 .It Va exec.jail_user
797 The user to run commands as, when running in the jail environment.
798 The default is to run the commands as the current user.
799 .It Va exec.system_jail_user
800 This boolean option looks for the
804 file, instead of in the jail's file.
805 .It Va exec.system_user
806 The user to run commands as, when running in the system environment.
807 The default is to run the commands as the current user.
809 The maximum amount of time to wait for a command to complete, in
811 If a command is still running after this timeout has passed,
812 the jail will not be created or removed, as appropriate.
813 .It Va exec.consolelog
814 A file to direct command output (stdout and stderr) to.
816 The FIB (routing table) to set when running commands inside the jail.
818 The maximum amount of time to wait for a jail's processes to exit
821 signal (which happens after the
823 commands have completed).
824 After this many seconds have passed, the jail will be removed, which
825 will kill any remaining processes.
826 If this is set to zero, no
828 is sent and the jail is immediately removed.
829 The default is 10 seconds.
831 A network interface to add the jail's IP addresses
836 An alias for each address will be added to the interface before the
837 jail is created, and will be removed from the interface after the
840 In addition to the IP addresses that are passed to the kernel, an
841 interface, netmask and additional parameters (as supported by
843 may also be specified, in the form
844 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
845 If an interface is given before the IP address, an alias for the address
846 will be added to that interface, as it is with the
849 If a netmask in either dotted-quad or CIDR form is given
850 after an IP address, it will be used when adding the IP alias.
851 If additional parameters are specified then they will also be used when
854 In addition to the IP addresses that are passed to the kernel,
855 an interface, prefix and additional parameters (as supported by
857 may also be specified, in the form
858 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
859 .It Va vnet.interface
860 A network interface to give to a vnet-enabled jail after is it created.
861 The interface will automatically be released when the jail is removed.
865 parameter and add all IP addresses returned by the resolver
866 to the list of addresses
871 This may affect default address selection for outgoing IPv4 connections
873 The address first returned by the resolver for each address family
874 will be used as the primary address.
876 A filesystem to mount before creating the jail (and to unmount after
877 removing it), given as a single
883 format file containing filesystems to mount before creating a jail.
887 filesystem on the chrooted
889 directory, and apply the ruleset in the
891 parameter (or a default of ruleset 4: devfsrules_jail)
892 to restrict the devices visible inside the jail.
896 filesystem on the chrooted
902 filesystem on the chrooted
906 Allow making changes to a
910 Specify a jail (or jails) that this jail depends on.
911 When this jail is to be created, any jail(s) it depends on must already exist.
912 If not, they will be created automatically, up to the completion of the last
914 command, before any action will taken to create this jail.
915 When jails are removed the opposite is true:
916 this jail will be removed, up to the last
918 command, before any jail(s) it depends on are stopped.
921 Jails are typically set up using one of two philosophies: either to
922 constrain a specific application (possibly running with privilege), or
924 .Dq "virtual system image"
925 running a variety of daemons and services.
926 In both cases, a fairly complete file system install of
929 required, so as to provide the necessary command line tools, daemons,
930 libraries, application configuration files, etc.
931 However, for a virtual server configuration, a fair amount of
932 additional work is required so as to replace the
935 This manual page documents the configuration steps necessary to support
936 either of these steps, although the configuration steps may need to be
937 refined based on local requirements.
938 .Ss "Setting up a Jail Directory Tree"
939 To set up a jail directory tree containing an entire
941 distribution, the following
943 command script can be used:
948 make world DESTDIR=$D
949 make distribution DESTDIR=$D
952 In many cases this example would put far more in the jail than needed.
953 In the other extreme case a jail might contain only one file:
954 the executable to be run in the jail.
956 We recommend experimentation, and caution that it is a lot easier to
959 jail and remove things until it stops working,
960 than it is to start with a
962 jail and add things until it works.
963 .Ss "Setting Up a Jail"
964 Do what was described in
965 .Sx "Setting Up a Jail Directory Tree"
966 to build the jail directory tree.
967 For the sake of this example, we will
968 assume you built it in
969 .Pa /data/jail/testjail ,
972 Substitute below as needed with your
973 own directory, IP address, and hostname.
974 .Ss "Setting up the Host Environment"
975 First, set up the real system's environment to be
977 For consistency, we will refer to the parent box as the
978 .Dq "host environment" ,
979 and to the jailed virtual machine as the
980 .Dq "jail environment" .
981 Since jails are implemented using IP aliases, one of the first things to do
982 is to disable IP services on the host system that listen on all local
983 IP addresses for a service.
984 If a network service is present in the host environment that binds all
985 available IP addresses rather than specific IP addresses, it may service
986 requests sent to jail IP addresses if the jail did not bind the port.
989 to only listen on the
990 appropriate IP address, and so forth.
993 in the host environment:
994 .Bd -literal -offset indent
996 inetd_flags="-wW -a 192.0.2.23"
1001 is the native IP address for the host system, in this example.
1002 Daemons that run out of
1004 can be easily configured to use only the specified host IP address.
1006 will need to be manually configured \(em for some this is possible through
1008 flags entries; for others it is necessary to modify per-application
1009 configuration files, or to recompile the application.
1010 The following frequently deployed services must have their individual
1011 configuration files modified to limit the application to listening
1012 to a specific IP address:
1016 it is necessary to modify
1017 .Pa /etc/ssh/sshd_config .
1021 it is necessary to modify
1022 .Pa /etc/mail/sendmail.cf .
1026 it is necessary to modify
1027 .Pa /etc/namedb/named.conf .
1029 In addition, a number of services must be recompiled in order to run
1030 them in the host environment.
1031 This includes most applications providing services using
1038 In general, applications for which it is not possible to specify which
1039 IP address to bind should not be run in the host environment unless they
1040 should also service requests sent to jail IP addresses.
1042 NFS from the host environment may also cause confusion, and cannot be
1043 easily reconfigured to use only specific IPs, as some NFS services are
1044 hosted directly from the kernel.
1045 Any third-party network software running
1046 in the host environment should also be checked and configured so that it
1047 does not bind all IP addresses, which would result in those services also
1048 appearing to be offered by the jail environments.
1051 these daemons have been disabled or fixed in the host environment, it is
1052 best to reboot so that all daemons are in a known state, to reduce the
1053 potential for confusion later (such as finding that when you send mail
1054 to a jail, and its sendmail is down, the mail is delivered to the host,
1056 .Ss "Configuring the Jail"
1057 Start any jail for the first time without configuring the network
1058 interface so that you can clean it up a little and set up accounts.
1060 with any machine (virtual or not), you will need to set a root password, time
1062 Some of these steps apply only if you intend to run a full virtual server
1063 inside the jail; others apply both for constraining a particular application
1064 or for running a virtual server.
1066 Start a shell in the jail:
1067 .Bd -literal -offset indent
1068 jail -c path=/data/jail/testjail mount.devfs \\
1069 host.hostname=testhostname ip4.addr=192.0.2.100 \\
1073 Assuming no errors, you will end up with a shell prompt within the jail.
1076 and do the post-install configuration to set various configuration options,
1077 or perform these actions manually by editing
1081 .Bl -bullet -offset indent -compact
1084 .Pa /etc/resolv.conf
1085 so that name resolution within the jail will work correctly.
1093 Set a root password, probably different from the real host system.
1097 Add accounts for users in the jail environment.
1099 Install any packages the environment requires.
1102 You may also want to perform any package-specific configuration (web servers,
1103 SSH servers, etc), patch up
1104 .Pa /etc/syslog.conf
1105 so it logs as you would like, etc.
1106 If you are not using a virtual server, you may wish to modify
1108 in the host environment to listen on the syslog socket in the jail
1109 environment; in this example, the syslog socket would be stored in
1110 .Pa /data/jail/testjail/var/run/log .
1112 Exit from the shell, and the jail will be shut down.
1113 .Ss "Starting the Jail"
1114 You are now ready to restart the jail and bring up the environment with
1115 all of its daemons and other programs.
1116 Create an entry for the jail in
1117 .Pa /etc/jail.conf :
1118 .Bd -literal -offset indent
1120 path = /tmp/jail/testjail;
1122 host.hostname = testhostname;
1123 ip4.addr = 192.0.2.100;
1125 exec.start = "/bin/sh /etc/rc";
1126 exec.stop = "/bin/sh /etc/rc.shutdown jail";
1130 To start a virtual server environment,
1132 is run to launch various daemons and services, and
1133 .Pa /etc/rc.shutdown
1134 is run to shut them down when the jail is removed.
1135 If you are running a single application in the jail,
1136 substitute the command used to start the application for
1137 .Dq /bin/sh /etc/rc ;
1138 there may be some script available to cleanly shut down the application,
1139 or it may be sufficient to go without a stop command, and have
1145 Start the jail by running:
1146 .Bd -literal -offset indent
1150 A few warnings may be produced; however, it should all work properly.
1151 You should be able to see
1154 and other processes running within the jail using
1158 flag appearing beside jailed processes.
1159 To see an active list of jails, use
1163 is enabled in the jail environment, you should be able to
1165 to the hostname or IP address of the jailed environment, and log
1166 in using the accounts you created previously.
1168 It is possible to have jails started at boot time.
1173 for more information.
1174 .Ss "Managing the Jail"
1175 Normal machine shutdown commands, such as
1180 cannot be used successfully within the jail.
1181 To kill all processes from within a jail, you may use one of the
1182 following commands, depending on what you want to accomplish:
1183 .Bd -literal -offset indent
1192 signals to all processes in the jail \(em be careful not to run this from
1193 the host environment!
1194 Once all of the jail's processes have died, unless the jail was created
1197 parameter, the jail will be removed.
1199 the intended use of the jail, you may also want to run
1200 .Pa /etc/rc.shutdown
1201 from within the jail.
1203 To shut down the jail from the outside, simply remove it with
1206 which will run any commands specified by
1212 to any remaining jailed processes.
1215 .Pa /proc/ Ns Ar pid Ns Pa /status
1216 file contains, as its last field, the name of the jail in which the
1219 to indicate that the process is not running within a jail.
1222 command also shows a
1224 flag for processes in a jail.
1226 You can also list/kill processes based on their jail ID.
1227 To show processes and their jail ID, use the following command:
1229 .Dl "ps ax -o pid,jid,args"
1231 To show and then kill processes in jail number 3 use the following commands:
1232 .Bd -literal -offset indent
1239 .Ss "Jails and File Systems"
1240 It is not possible to
1244 any file system inside a jail unless the file system is marked
1245 jail-friendly, the jail's
1247 parameter is set, and the jail's
1249 parameter is lower than 2.
1251 Multiple jails sharing the same file system can influence each other.
1252 For example, a user in one jail can fill the file system,
1253 leaving no space for processes in the other jail.
1256 to prevent this will not work either, as the file system quotas
1257 are not aware of jails but only look at the user and group IDs.
1258 This means the same user ID in two jails share a single file
1260 One would need to use one file system per jail to make this work.
1261 .Ss "Sysctl MIB Entries"
1263 .Va security.jail.jailed
1264 can be used to determine if a process is running inside a jail (value
1265 is one) or not (value is zero).
1268 .Va security.jail.max_af_ips
1269 determines how may address per address family a jail may have.
1272 Some MIB variables have per-jail settings.
1273 Changes to these variables by a jailed process do not affect the host
1274 environment, only the jail environment.
1276 .Va kern.securelevel ,
1277 .Va security.bsd.suser_enabled ,
1279 .Va kern.domainname ,
1283 .Ss "Hierarchical Jails"
1286 parameter, processes within a jail may be able to create jails of their own.
1287 These child jails are kept in a hierarchy, with jails only able to see and/or
1288 modify the jails they created (or those jails' children).
1289 Each jail has a read-only
1291 parameter, containing the
1293 of the jail that created it; a
1295 of 0 indicates the jail is a child of the current jail (or is a top-level
1296 jail if the current process isn't jailed).
1298 Jailed processes are not allowed to confer greater permissions than they
1299 themselves are given, e.g., if a jail is created with
1301 it is not able to create a jail with
1304 Similarly, such restrictions as
1308 may not be bypassed in child jails.
1310 A child jail may in turn create its own child jails if its own
1312 parameter is set (remember it is zero by default).
1313 These jails are visible to and can be modified by their parent and all
1316 Jail names reflect this hierarchy, with a full name being an MIB-type string
1318 For example, if a base system process creates a jail
1320 and a process under that jail creates another jail
1322 then the second jail will be seen as
1324 in the base system (though it is only seen as
1326 to any processes inside jail
1328 Jids on the other hand exist in a single space, and each jail must have a
1331 Like the names, a child jail's
1333 appears relative to its creator's own
1335 This is by virtue of the child jail being created in the chrooted
1336 environment of the first jail.
1377 Hierarchical/extensible jails were introduced in
1379 The configuration file was introduced in
1383 The jail feature was written by
1384 .An Poul-Henning Kamp
1386 who contributed it to
1390 wrote the extended documentation, found a few bugs, added
1391 a few new features, and cleaned up the userland jail environment.
1394 added multi-IP jail support for IPv4 and IPv6 based on a patch
1396 .An Pawel Jakub Dawidek
1400 added the extensible jail parameters, hierarchical jails,
1401 and the configuration file.
1403 It might be a good idea to add an
1404 address alias flag such that daemons listening on all IPs
1406 will not bind on that address, which would facilitate building a safe
1407 host environment such that host daemons do not impose on services offered
1409 Currently, the simplest answer is to minimize services
1410 offered on the host, possibly limiting it to services offered from
1412 which is easily configurable.
1414 Great care should be taken when managing directories visible within the jail.
1415 For example, if a jailed process has its current working directory set to a
1416 directory that is moved out of the jail's chroot, then the process may gain
1417 access to the file space outside of the jail.
1418 It is recommended that directories always be copied, rather than moved, out
1421 In addition, there are several ways in which an unprivileged user
1422 outside the jail can cooperate with a privileged user inside the jail
1423 and thereby obtain elevated privileges in the host environment.
1424 Most of these attacks can be mitigated by ensuring that the jail root
1425 is not accessible to unprivileged users in the host environment.
1426 Regardless, as a general rule, untrusted users with privileged access
1427 to a jail should not be given access to the host environment.