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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.
593 Kernel modules may add their own parameters, which only exist when the
595 These are typically headed under a parameter named after the module,
598 to give the jail full use of the module,
600 to encapsulate the jail in some module-specific way,
603 to make the module unavailable to the jail.
604 There also may be other parameters to define jail behavior within the module.
605 Module-specific parameters include:
606 .Bl -tag -width indent
607 .It Va allow.mount.fdescfs
608 privileged users inside the jail will be able to mount and unmount the
610 This permission is effective only together with
614 is set to a value lower than 2.
615 .It Va allow.mount.fusefs
616 privileged users inside the jail will be able to mount and unmount
617 fuse-based file systems.
618 This permission is effective only together with
622 is set to a value lower than 2.
623 .It Va allow.mount.nullfs
624 privileged users inside the jail will be able to mount and unmount the
626 This permission is effective only together with
630 is set to a value lower than 2.
631 .It Va allow.mount.procfs
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.linprocfs
640 privileged users inside the jail will be able to mount and unmount the
641 linprocfs file system.
642 This permission is effective only together with
646 is set to a value lower than 2.
647 .It Va allow.mount.linsysfs
648 privileged users inside the jail will be able to mount and unmount the
649 linsysfs file system.
650 This permission is effective only together with
654 is set to a value lower than 2.
655 .It Va allow.mount.tmpfs
656 privileged users inside the jail will be able to mount and unmount the
658 This permission is effective only together with
662 is set to a value lower than 2.
663 .It Va allow.mount.zfs
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.
673 for information on how to configure the ZFS filesystem to operate from
678 This flag is only available when the
680 kernel module is loaded.
682 Determine how a jail's Linux emulation environment appears.
685 will keep the same environment, and
687 will give the jail its own environment (still originally inherited when
688 the jail is created).
689 .It Va linux.osname , linux.osrelease , linux.oss_version
690 The Linux OS name, OS release, and OSS version associated with this jail.
692 Allow access to SYSV IPC message primitives.
695 all IPC objects on the system are visible to this jail, whether they
696 were created by the jail itself, the base system, or other jails.
699 the jail will have its own key namespace, and can only see the objects
701 the system (or parent jail) has access to the jail's objects, but not to
705 the jail cannot perform any sysvmsg-related system calls.
706 .It Va sysvsem, sysvshm
707 Allow access to SYSV IPC semaphore and shared memory primitives, in the
712 There are pseudo-parameters that are not passed to the kernel, but are
715 to set up the jail environment, often by running specified commands
716 when jails are created or removed.
719 command parameters are
721 command lines that are run in either the system or jail environment.
722 They may be given multiple values, which would run the specified
723 commands in sequence.
724 All commands must succeed (return a zero exit status), or the jail will
725 not be created or removed, as appropriate.
727 The pseudo-parameters are:
728 .Bl -tag -width indent
730 Command(s) to run in the system environment to prepare a jail for creation.
731 These commands are executed before assigning IP addresses and mounting
732 filesystems, so they may be used to create a new jail filesystem if it does
735 Command(s) to run in the system environment before a jail is created.
737 Command(s) to run in the system environment right after a jail has been
738 created, but before commands (or services) get executed in the jail.
740 Command(s) to run in the jail environment when a jail is created.
741 A typical command to run is
746 for use when specifying a jail directly on the command line.
747 Unlike other parameters whose value is a single string,
749 uses the remainder of the
751 command line as its own arguments.
752 .It Va exec.poststart
753 Command(s) to run in the system environment after a jail is created,
756 commands have completed.
758 Command(s) to run in the system environment before a jail is removed.
760 Command(s) to run in the jail environment before a jail is removed,
763 commands have completed.
764 A typical command to run is
765 .Dq sh /etc/rc.shutdown jail .
767 Command(s) to run in the system environment after a jail is removed.
769 Command(s) to run in the system environment after all other actions are done.
770 These commands are executed after unmounting filesystems and removing IP
771 addresses, so they may be used to remove a jail filesystem if it is no longer
774 Run commands in a clean environment.
775 The environment is discarded except for
776 .Ev HOME , SHELL , TERM
782 are set to the target login's default values.
784 is set to the target login.
786 is imported from the current environment.
787 The environment variables from the login class capability database for the
788 target login are also set.
789 .It Va exec.jail_user
790 The user to run commands as, when running in the jail environment.
791 The default is to run the commands as the current user.
792 .It Va exec.system_jail_user
793 This boolean option looks for the
797 file, instead of in the jail's file.
798 .It Va exec.system_user
799 The user to run commands as, when running in the system environment.
800 The default is to run the commands as the current user.
802 The maximum amount of time to wait for a command to complete, in
804 If a command is still running after this timeout has passed,
805 the jail will not be created or removed, as appropriate.
806 .It Va exec.consolelog
807 A file to direct command output (stdout and stderr) to.
809 The FIB (routing table) to set when running commands inside the jail.
811 The maximum amount of time to wait for a jail's processes to exit
814 signal (which happens after the
816 commands have completed).
817 After this many seconds have passed, the jail will be removed, which
818 will kill any remaining processes.
819 If this is set to zero, no
821 is sent and the jail is immediately removed.
822 The default is 10 seconds.
824 A network interface to add the jail's IP addresses
829 An alias for each address will be added to the interface before the
830 jail is created, and will be removed from the interface after the
833 In addition to the IP addresses that are passed to the kernel, an
834 interface, netmask and additional parameters (as supported by
836 may also be specified, in the form
837 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
838 If an interface is given before the IP address, an alias for the address
839 will be added to that interface, as it is with the
842 If a netmask in either dotted-quad or CIDR form is given
843 after an IP address, it will be used when adding the IP alias.
844 If additional parameters are specified then they will also be used when
847 In addition to the IP addresses that are passed to the kernel,
848 an interface, prefix and additional parameters (as supported by
850 may also be specified, in the form
851 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
852 .It Va vnet.interface
853 A network interface to give to a vnet-enabled jail after is it created.
854 The interface will automatically be released when the jail is removed.
858 parameter and add all IP addresses returned by the resolver
859 to the list of addresses
864 This may affect default address selection for outgoing IPv4 connections
866 The address first returned by the resolver for each address family
867 will be used as the primary address.
869 A filesystem to mount before creating the jail (and to unmount after
870 removing it), given as a single
876 format file containing filesystems to mount before creating a jail.
880 filesystem on the chrooted
882 directory, and apply the ruleset in the
884 parameter (or a default of ruleset 4: devfsrules_jail)
885 to restrict the devices visible inside the jail.
889 filesystem on the chrooted
895 filesystem on the chrooted
899 Allow making changes to a
903 Specify a jail (or jails) that this jail depends on.
904 When this jail is to be created, any jail(s) it depends on must already exist.
905 If not, they will be created automatically, up to the completion of the last
907 command, before any action will taken to create this jail.
908 When jails are removed the opposite is true:
909 this jail will be removed, up to the last
911 command, before any jail(s) it depends on are stopped.
914 Jails are typically set up using one of two philosophies: either to
915 constrain a specific application (possibly running with privilege), or
917 .Dq "virtual system image"
918 running a variety of daemons and services.
919 In both cases, a fairly complete file system install of
922 required, so as to provide the necessary command line tools, daemons,
923 libraries, application configuration files, etc.
924 However, for a virtual server configuration, a fair amount of
925 additional work is required so as to replace the
928 This manual page documents the configuration steps necessary to support
929 either of these steps, although the configuration steps may need to be
930 refined based on local requirements.
931 .Ss "Setting up a Jail Directory Tree"
932 To set up a jail directory tree containing an entire
934 distribution, the following
936 command script can be used:
941 make world DESTDIR=$D
942 make distribution DESTDIR=$D
945 In many cases this example would put far more in the jail than needed.
946 In the other extreme case a jail might contain only one file:
947 the executable to be run in the jail.
949 We recommend experimentation, and caution that it is a lot easier to
952 jail and remove things until it stops working,
953 than it is to start with a
955 jail and add things until it works.
956 .Ss "Setting Up a Jail"
957 Do what was described in
958 .Sx "Setting Up a Jail Directory Tree"
959 to build the jail directory tree.
960 For the sake of this example, we will
961 assume you built it in
962 .Pa /data/jail/testjail ,
965 Substitute below as needed with your
966 own directory, IP address, and hostname.
967 .Ss "Setting up the Host Environment"
968 First, set up the real system's environment to be
970 For consistency, we will refer to the parent box as the
971 .Dq "host environment" ,
972 and to the jailed virtual machine as the
973 .Dq "jail environment" .
974 Since jails are implemented using IP aliases, one of the first things to do
975 is to disable IP services on the host system that listen on all local
976 IP addresses for a service.
977 If a network service is present in the host environment that binds all
978 available IP addresses rather than specific IP addresses, it may service
979 requests sent to jail IP addresses if the jail did not bind the port.
982 to only listen on the
983 appropriate IP address, and so forth.
986 in the host environment:
987 .Bd -literal -offset indent
989 inetd_flags="-wW -a 192.0.2.23"
994 is the native IP address for the host system, in this example.
995 Daemons that run out of
997 can be easily configured to use only the specified host IP address.
999 will need to be manually configured \(em for some this is possible through
1001 flags entries; for others it is necessary to modify per-application
1002 configuration files, or to recompile the application.
1003 The following frequently deployed services must have their individual
1004 configuration files modified to limit the application to listening
1005 to a specific IP address:
1009 it is necessary to modify
1010 .Pa /etc/ssh/sshd_config .
1014 it is necessary to modify
1015 .Pa /etc/mail/sendmail.cf .
1019 it is necessary to modify
1020 .Pa /etc/namedb/named.conf .
1022 In addition, a number of services must be recompiled in order to run
1023 them in the host environment.
1024 This includes most applications providing services using
1031 In general, applications for which it is not possible to specify which
1032 IP address to bind should not be run in the host environment unless they
1033 should also service requests sent to jail IP addresses.
1035 NFS from the host environment may also cause confusion, and cannot be
1036 easily reconfigured to use only specific IPs, as some NFS services are
1037 hosted directly from the kernel.
1038 Any third-party network software running
1039 in the host environment should also be checked and configured so that it
1040 does not bind all IP addresses, which would result in those services also
1041 appearing to be offered by the jail environments.
1044 these daemons have been disabled or fixed in the host environment, it is
1045 best to reboot so that all daemons are in a known state, to reduce the
1046 potential for confusion later (such as finding that when you send mail
1047 to a jail, and its sendmail is down, the mail is delivered to the host,
1049 .Ss "Configuring the Jail"
1050 Start any jail for the first time without configuring the network
1051 interface so that you can clean it up a little and set up accounts.
1053 with any machine (virtual or not), you will need to set a root password, time
1055 Some of these steps apply only if you intend to run a full virtual server
1056 inside the jail; others apply both for constraining a particular application
1057 or for running a virtual server.
1059 Start a shell in the jail:
1060 .Bd -literal -offset indent
1061 jail -c path=/data/jail/testjail mount.devfs \\
1062 host.hostname=testhostname ip4.addr=192.0.2.100 \\
1066 Assuming no errors, you will end up with a shell prompt within the jail.
1069 and do the post-install configuration to set various configuration options,
1070 or perform these actions manually by editing
1074 .Bl -bullet -offset indent -compact
1077 .Pa /etc/resolv.conf
1078 so that name resolution within the jail will work correctly.
1086 Set a root password, probably different from the real host system.
1090 Add accounts for users in the jail environment.
1092 Install any packages the environment requires.
1095 You may also want to perform any package-specific configuration (web servers,
1096 SSH servers, etc), patch up
1097 .Pa /etc/syslog.conf
1098 so it logs as you would like, etc.
1099 If you are not using a virtual server, you may wish to modify
1101 in the host environment to listen on the syslog socket in the jail
1102 environment; in this example, the syslog socket would be stored in
1103 .Pa /data/jail/testjail/var/run/log .
1105 Exit from the shell, and the jail will be shut down.
1106 .Ss "Starting the Jail"
1107 You are now ready to restart the jail and bring up the environment with
1108 all of its daemons and other programs.
1109 Create an entry for the jail in
1110 .Pa /etc/jail.conf :
1111 .Bd -literal -offset indent
1113 path = /tmp/jail/testjail;
1115 host.hostname = testhostname;
1116 ip4.addr = 192.0.2.100;
1118 exec.start = "/bin/sh /etc/rc";
1119 exec.stop = "/bin/sh /etc/rc.shutdown jail";
1123 To start a virtual server environment,
1125 is run to launch various daemons and services, and
1126 .Pa /etc/rc.shutdown
1127 is run to shut them down when the jail is removed.
1128 If you are running a single application in the jail,
1129 substitute the command used to start the application for
1130 .Dq /bin/sh /etc/rc ;
1131 there may be some script available to cleanly shut down the application,
1132 or it may be sufficient to go without a stop command, and have
1138 Start the jail by running:
1139 .Bd -literal -offset indent
1143 A few warnings may be produced; however, it should all work properly.
1144 You should be able to see
1147 and other processes running within the jail using
1151 flag appearing beside jailed processes.
1152 To see an active list of jails, use
1156 is enabled in the jail environment, you should be able to
1158 to the hostname or IP address of the jailed environment, and log
1159 in using the accounts you created previously.
1161 It is possible to have jails started at boot time.
1166 for more information.
1167 .Ss "Managing the Jail"
1168 Normal machine shutdown commands, such as
1173 cannot be used successfully within the jail.
1174 To kill all processes from within a jail, you may use one of the
1175 following commands, depending on what you want to accomplish:
1176 .Bd -literal -offset indent
1185 signals to all processes in the jail \(em be careful not to run this from
1186 the host environment!
1187 Once all of the jail's processes have died, unless the jail was created
1190 parameter, the jail will be removed.
1192 the intended use of the jail, you may also want to run
1193 .Pa /etc/rc.shutdown
1194 from within the jail.
1196 To shut down the jail from the outside, simply remove it with
1199 which will run any commands specified by
1205 to any remaining jailed processes.
1208 .Pa /proc/ Ns Ar pid Ns Pa /status
1209 file contains, as its last field, the name of the jail in which the
1212 to indicate that the process is not running within a jail.
1215 command also shows a
1217 flag for processes in a jail.
1219 You can also list/kill processes based on their jail ID.
1220 To show processes and their jail ID, use the following command:
1222 .Dl "ps ax -o pid,jid,args"
1224 To show and then kill processes in jail number 3 use the following commands:
1225 .Bd -literal -offset indent
1232 .Ss "Jails and File Systems"
1233 It is not possible to
1237 any file system inside a jail unless the file system is marked
1238 jail-friendly, the jail's
1240 parameter is set, and the jail's
1242 parameter is lower than 2.
1244 Multiple jails sharing the same file system can influence each other.
1245 For example, a user in one jail can fill the file system,
1246 leaving no space for processes in the other jail.
1249 to prevent this will not work either, as the file system quotas
1250 are not aware of jails but only look at the user and group IDs.
1251 This means the same user ID in two jails share a single file
1253 One would need to use one file system per jail to make this work.
1254 .Ss "Sysctl MIB Entries"
1256 .Va security.jail.jailed
1257 can be used to determine if a process is running inside a jail (value
1258 is one) or not (value is zero).
1261 .Va security.jail.max_af_ips
1262 determines how may address per address family a jail may have.
1265 Some MIB variables have per-jail settings.
1266 Changes to these variables by a jailed process do not affect the host
1267 environment, only the jail environment.
1269 .Va kern.securelevel ,
1271 .Va kern.domainname ,
1275 .Ss "Hierarchical Jails"
1278 parameter, processes within a jail may be able to create jails of their own.
1279 These child jails are kept in a hierarchy, with jails only able to see and/or
1280 modify the jails they created (or those jails' children).
1281 Each jail has a read-only
1283 parameter, containing the
1285 of the jail that created it; a
1287 of 0 indicates the jail is a child of the current jail (or is a top-level
1288 jail if the current process isn't jailed).
1290 Jailed processes are not allowed to confer greater permissions than they
1291 themselves are given, e.g., if a jail is created with
1293 it is not able to create a jail with
1296 Similarly, such restrictions as
1300 may not be bypassed in child jails.
1302 A child jail may in turn create its own child jails if its own
1304 parameter is set (remember it is zero by default).
1305 These jails are visible to and can be modified by their parent and all
1308 Jail names reflect this hierarchy, with a full name being an MIB-type string
1310 For example, if a base system process creates a jail
1312 and a process under that jail creates another jail
1314 then the second jail will be seen as
1316 in the base system (though it is only seen as
1318 to any processes inside jail
1320 Jids on the other hand exist in a single space, and each jail must have a
1323 Like the names, a child jail's
1325 appears relative to its creator's own
1327 This is by virtue of the child jail being created in the chrooted
1328 environment of the first jail.
1369 Hierarchical/extensible jails were introduced in
1371 The configuration file was introduced in
1375 The jail feature was written by
1376 .An Poul-Henning Kamp
1378 who contributed it to
1382 wrote the extended documentation, found a few bugs, added
1383 a few new features, and cleaned up the userland jail environment.
1386 added multi-IP jail support for IPv4 and IPv6 based on a patch
1388 .An Pawel Jakub Dawidek
1392 added the extensible jail parameters, hierarchical jails,
1393 and the configuration file.
1395 It might be a good idea to add an
1396 address alias flag such that daemons listening on all IPs
1398 will not bind on that address, which would facilitate building a safe
1399 host environment such that host daemons do not impose on services offered
1401 Currently, the simplest answer is to minimize services
1402 offered on the host, possibly limiting it to services offered from
1404 which is easily configurable.
1406 Great care should be taken when managing directories visible within the jail.
1407 For example, if a jailed process has its current working directory set to a
1408 directory that is moved out of the jail's chroot, then the process may gain
1409 access to the file space outside of the jail.
1410 It is recommended that directories always be copied, rather than moved, out
1413 In addition, there are several ways in which an unprivileged user
1414 outside the jail can cooperate with a privileged user inside the jail
1415 and thereby obtain elevated privileges in the host environment.
1416 Most of these attacks can be mitigated by ensuring that the jail root
1417 is not accessible to unprivileged users in the host environment.
1418 Regardless, as a general rule, untrusted users with privileged access
1419 to a jail should not be given access to the host environment.