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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
592 daemons are permitted to run inside a vnet-enabled jail.
593 The kernel must have been compiled with the
599 for this to be available.
600 .It Va allow.reserved_ports
601 The jail root may bind to ports lower than 1024.
602 .It Va allow.unprivileged_proc_debug
603 Unprivileged processes in the jail may use debugging facilities.
605 The value of the jail's
606 .Va security.bsd.suser_enabled
608 The super-user will be disabled automatically if its parent system has it
610 The super-user is enabled by default.
614 Kernel modules may add their own parameters, which only exist when the
616 These are typically headed under a parameter named after the module,
619 to give the jail full use of the module,
621 to encapsulate the jail in some module-specific way,
624 to make the module unavailable to the jail.
625 There also may be other parameters to define jail behavior within the module.
626 Module-specific parameters include:
627 .Bl -tag -width indent
628 .It Va allow.mount.fdescfs
629 privileged users inside the jail will be able to mount and unmount the
631 This permission is effective only together with
635 is set to a value lower than 2.
636 .It Va allow.mount.fusefs
637 privileged users inside the jail will be able to mount and unmount
638 fuse-based file systems.
639 This permission is effective only together with
643 is set to a value lower than 2.
644 .It Va allow.mount.nullfs
645 privileged users inside the jail will be able to mount and unmount the
647 This permission is effective only together with
651 is set to a value lower than 2.
652 .It Va allow.mount.procfs
653 privileged users inside the jail will be able to mount and unmount the
655 This permission is effective only together with
659 is set to a value lower than 2.
660 .It Va allow.mount.linprocfs
661 privileged users inside the jail will be able to mount and unmount the
662 linprocfs file system.
663 This permission is effective only together with
667 is set to a value lower than 2.
668 .It Va allow.mount.linsysfs
669 privileged users inside the jail will be able to mount and unmount the
670 linsysfs file system.
671 This permission is effective only together with
675 is set to a value lower than 2.
676 .It Va allow.mount.tmpfs
677 privileged users inside the jail will be able to mount and unmount the
679 This permission is effective only together with
683 is set to a value lower than 2.
684 .It Va allow.mount.zfs
685 privileged users inside the jail will be able to mount and unmount the
687 This permission is effective only together with
691 is set to a value lower than 2.
694 for information on how to configure the ZFS filesystem to operate from
699 This flag is only available when the
701 kernel module is loaded.
703 Determine how a jail's Linux emulation environment appears.
706 will keep the same environment, and
708 will give the jail its own environment (still originally inherited when
709 the jail is created).
710 .It Va linux.osname , linux.osrelease , linux.oss_version
711 The Linux OS name, OS release, and OSS version associated with this jail.
713 Allow access to SYSV IPC message primitives.
716 all IPC objects on the system are visible to this jail, whether they
717 were created by the jail itself, the base system, or other jails.
720 the jail will have its own key namespace, and can only see the objects
722 the system (or parent jail) has access to the jail's objects, but not to
726 the jail cannot perform any sysvmsg-related system calls.
727 .It Va sysvsem, sysvshm
728 Allow access to SYSV IPC semaphore and shared memory primitives, in the
733 There are pseudo-parameters that are not passed to the kernel, but are
736 to set up the jail environment, often by running specified commands
737 when jails are created or removed.
740 command parameters are
742 command lines that are run in either the system or jail environment.
743 They may be given multiple values, which would run the specified
744 commands in sequence.
745 All commands must succeed (return a zero exit status), or the jail will
746 not be created or removed, as appropriate.
748 The pseudo-parameters are:
749 .Bl -tag -width indent
751 Command(s) to run in the system environment to prepare a jail for creation.
752 These commands are executed before assigning IP addresses and mounting
753 filesystems, so they may be used to create a new jail filesystem if it does
756 Command(s) to run in the system environment before a jail is created.
758 Command(s) to run in the system environment right after a jail has been
759 created, but before commands (or services) get executed in the jail.
761 Command(s) to run in the jail environment when a jail is created.
762 A typical command to run is
767 for use when specifying a jail directly on the command line.
768 Unlike other parameters whose value is a single string,
770 uses the remainder of the
772 command line as its own arguments.
773 .It Va exec.poststart
774 Command(s) to run in the system environment after a jail is created,
777 commands have completed.
779 Command(s) to run in the system environment before a jail is removed.
781 Command(s) to run in the jail environment before a jail is removed,
784 commands have completed.
785 A typical command to run is
786 .Dq sh /etc/rc.shutdown jail .
788 Command(s) to run in the system environment after a jail is removed.
790 Command(s) to run in the system environment after all other actions are done.
791 These commands are executed after unmounting filesystems and removing IP
792 addresses, so they may be used to remove a jail filesystem if it is no longer
795 Run commands in a clean environment.
796 The environment is discarded except for
797 .Ev HOME , SHELL , TERM
803 are set to the target login's default values.
805 is set to the target login.
807 is imported from the current environment.
808 The environment variables from the login class capability database for the
809 target login are also set.
810 .It Va exec.jail_user
811 The user to run commands as, when running in the jail environment.
812 The default is to run the commands as the current user.
813 .It Va exec.system_jail_user
814 This boolean option looks for the
818 file, instead of in the jail's file.
819 .It Va exec.system_user
820 The user to run commands as, when running in the system environment.
821 The default is to run the commands as the current user.
823 The maximum amount of time to wait for a command to complete, in
825 If a command is still running after this timeout has passed,
826 the jail will not be created or removed, as appropriate.
827 .It Va exec.consolelog
828 A file to direct command output (stdout and stderr) to.
830 The FIB (routing table) to set when running commands inside the jail.
832 The maximum amount of time to wait for a jail's processes to exit
835 signal (which happens after the
837 commands have completed).
838 After this many seconds have passed, the jail will be removed, which
839 will kill any remaining processes.
840 If this is set to zero, no
842 is sent and the jail is immediately removed.
843 The default is 10 seconds.
845 A network interface to add the jail's IP addresses
850 An alias for each address will be added to the interface before the
851 jail is created, and will be removed from the interface after the
854 In addition to the IP addresses that are passed to the kernel, an
855 interface, netmask 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 netmask param ... .
859 If an interface is given before the IP address, an alias for the address
860 will be added to that interface, as it is with the
863 If a netmask in either dotted-quad or CIDR form is given
864 after an IP address, it will be used when adding the IP alias.
865 If additional parameters are specified then they will also be used when
868 In addition to the IP addresses that are passed to the kernel,
869 an interface, prefix and additional parameters (as supported by
871 may also be specified, in the form
872 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
873 .It Va vnet.interface
874 A network interface to give to a vnet-enabled jail after is it created.
875 The interface will automatically be released when the jail is removed.
879 parameter and add all IP addresses returned by the resolver
880 to the list of addresses
885 This may affect default address selection for outgoing IPv4 connections
887 The address first returned by the resolver for each address family
888 will be used as the primary address.
890 A filesystem to mount before creating the jail (and to unmount after
891 removing it), given as a single
897 format file containing filesystems to mount before creating a jail.
901 filesystem on the chrooted
903 directory, and apply the ruleset in the
905 parameter (or a default of ruleset 4: devfsrules_jail)
906 to restrict the devices visible inside the jail.
910 filesystem on the chrooted
916 filesystem on the chrooted
920 Allow making changes to a
924 Specify a jail (or jails) that this jail depends on.
925 When this jail is to be created, any jail(s) it depends on must already exist.
926 If not, they will be created automatically, up to the completion of the last
928 command, before any action will taken to create this jail.
929 When jails are removed the opposite is true:
930 this jail will be removed, up to the last
932 command, before any jail(s) it depends on are stopped.
935 Jails are typically set up using one of two philosophies: either to
936 constrain a specific application (possibly running with privilege), or
938 .Dq "virtual system image"
939 running a variety of daemons and services.
940 In both cases, a fairly complete file system install of
943 required, so as to provide the necessary command line tools, daemons,
944 libraries, application configuration files, etc.
945 However, for a virtual server configuration, a fair amount of
946 additional work is required so as to replace the
949 This manual page documents the configuration steps necessary to support
950 either of these steps, although the configuration steps may need to be
951 refined based on local requirements.
952 .Ss "Setting up a Jail Directory Tree"
953 To set up a jail directory tree containing an entire
955 distribution, the following
957 command script can be used:
958 .Bd -literal -offset indent
962 make world DESTDIR=$D
963 make distribution DESTDIR=$D
966 In many cases this example would put far more in the jail than needed.
967 In the other extreme case a jail might contain only one file:
968 the executable to be run in the jail.
970 We recommend experimentation, and caution that it is a lot easier to
973 jail and remove things until it stops working,
974 than it is to start with a
976 jail and add things until it works.
977 .Ss "Setting Up a Jail"
978 Do what was described in
979 .Sx "Setting Up a Jail Directory Tree"
980 to build the jail directory tree.
981 For the sake of this example, we will
982 assume you built it in
983 .Pa /data/jail/testjail ,
986 Substitute below as needed with your
987 own directory, IP address, and hostname.
988 .Ss "Setting up the Host Environment"
989 First, set up the real system's environment to be
991 For consistency, we will refer to the parent box as the
992 .Dq "host environment" ,
993 and to the jailed virtual machine as the
994 .Dq "jail environment" .
995 Since jails are implemented using IP aliases, one of the first things to do
996 is to disable IP services on the host system that listen on all local
997 IP addresses for a service.
998 If a network service is present in the host environment that binds all
999 available IP addresses rather than specific IP addresses, it may service
1000 requests sent to jail IP addresses if the jail did not bind the port.
1003 to only listen on the
1004 appropriate IP address, and so forth.
1005 Add the following to
1007 in the host environment:
1008 .Bd -literal -offset indent
1009 sendmail_enable="NO"
1010 inetd_flags="-wW -a 192.0.2.23"
1015 is the native IP address for the host system, in this example.
1016 Daemons that run out of
1018 can be easily configured to use only the specified host IP address.
1020 will need to be manually configured \(em for some this is possible through
1022 flags entries; for others it is necessary to modify per-application
1023 configuration files, or to recompile the application.
1024 The following frequently deployed services must have their individual
1025 configuration files modified to limit the application to listening
1026 to a specific IP address:
1030 it is necessary to modify
1031 .Pa /etc/ssh/sshd_config .
1035 it is necessary to modify
1036 .Pa /etc/mail/sendmail.cf .
1038 In addition, a number of services must be recompiled in order to run
1039 them in the host environment.
1040 This includes most applications providing services using
1047 In general, applications for which it is not possible to specify which
1048 IP address to bind should not be run in the host environment unless they
1049 should also service requests sent to jail IP addresses.
1051 NFS from the host environment may also cause confusion, and cannot be
1052 easily reconfigured to use only specific IPs, as some NFS services are
1053 hosted directly from the kernel.
1054 Any third-party network software running
1055 in the host environment should also be checked and configured so that it
1056 does not bind all IP addresses, which would result in those services also
1057 appearing to be offered by the jail environments.
1060 these daemons have been disabled or fixed in the host environment, it is
1061 best to reboot so that all daemons are in a known state, to reduce the
1062 potential for confusion later (such as finding that when you send mail
1063 to a jail, and its sendmail is down, the mail is delivered to the host,
1065 .Ss "Configuring the Jail"
1066 Start any jail for the first time without configuring the network
1067 interface so that you can clean it up a little and set up accounts.
1069 with any machine (virtual or not), you will need to set a root password, time
1071 Some of these steps apply only if you intend to run a full virtual server
1072 inside the jail; others apply both for constraining a particular application
1073 or for running a virtual server.
1075 Start a shell in the jail:
1076 .Bd -literal -offset indent
1077 jail -c path=/data/jail/testjail mount.devfs \\
1078 host.hostname=testhostname ip4.addr=192.0.2.100 \\
1082 Assuming no errors, you will end up with a shell prompt within the jail.
1085 and do the post-install configuration to set various configuration options,
1086 or perform these actions manually by editing
1090 .Bl -bullet -offset indent -compact
1093 .Pa /etc/resolv.conf
1094 so that name resolution within the jail will work correctly.
1102 Set a root password, probably different from the real host system.
1106 Add accounts for users in the jail environment.
1108 Install any packages the environment requires.
1111 You may also want to perform any package-specific configuration (web servers,
1112 SSH servers, etc), patch up
1113 .Pa /etc/syslog.conf
1114 so it logs as you would like, etc.
1115 If you are not using a virtual server, you may wish to modify
1117 in the host environment to listen on the syslog socket in the jail
1118 environment; in this example, the syslog socket would be stored in
1119 .Pa /data/jail/testjail/var/run/log .
1121 Exit from the shell, and the jail will be shut down.
1122 .Ss "Starting the Jail"
1123 You are now ready to restart the jail and bring up the environment with
1124 all of its daemons and other programs.
1125 Create an entry for the jail in
1126 .Pa /etc/jail.conf :
1127 .Bd -literal -offset indent
1129 path = /tmp/jail/testjail;
1131 host.hostname = testhostname;
1132 ip4.addr = 192.0.2.100;
1134 exec.start = "/bin/sh /etc/rc";
1135 exec.stop = "/bin/sh /etc/rc.shutdown jail";
1139 To start a virtual server environment,
1141 is run to launch various daemons and services, and
1142 .Pa /etc/rc.shutdown
1143 is run to shut them down when the jail is removed.
1144 If you are running a single application in the jail,
1145 substitute the command used to start the application for
1146 .Dq /bin/sh /etc/rc ;
1147 there may be some script available to cleanly shut down the application,
1148 or it may be sufficient to go without a stop command, and have
1154 Start the jail by running:
1155 .Bd -literal -offset indent
1159 A few warnings may be produced; however, it should all work properly.
1160 You should be able to see
1163 and other processes running within the jail using
1167 flag appearing beside jailed processes.
1168 To see an active list of jails, use
1172 is enabled in the jail environment, you should be able to
1174 to the hostname or IP address of the jailed environment, and log
1175 in using the accounts you created previously.
1177 It is possible to have jails started at boot time.
1182 for more information.
1183 .Ss "Managing the Jail"
1184 Normal machine shutdown commands, such as
1189 cannot be used successfully within the jail.
1190 To kill all processes from within a jail, you may use one of the
1191 following commands, depending on what you want to accomplish:
1192 .Bd -literal -offset indent
1201 signals to all processes in the jail \(em be careful not to run this from
1202 the host environment!
1203 Once all of the jail's processes have died, unless the jail was created
1206 parameter, the jail will be removed.
1208 the intended use of the jail, you may also want to run
1209 .Pa /etc/rc.shutdown
1210 from within the jail.
1212 To shut down the jail from the outside, simply remove it with:
1213 .Bd -literal -offset indent
1217 which will run any commands specified by
1223 to any remaining jailed processes.
1226 .Pa /proc/ Ns Ar pid Ns Pa /status
1227 file contains, as its last field, the name of the jail in which the
1230 to indicate that the process is not running within a jail.
1233 command also shows a
1235 flag for processes in a jail.
1237 You can also list/kill processes based on their jail ID.
1238 To show processes and their jail ID, use the following command:
1240 .Dl "ps ax -o pid,jid,args"
1242 To show and then kill processes in jail number 3 use the following commands:
1243 .Bd -literal -offset indent
1250 .Ss "Jails and File Systems"
1251 It is not possible to
1255 any file system inside a jail unless the file system is marked
1256 jail-friendly, the jail's
1258 parameter is set, and the jail's
1260 parameter is lower than 2.
1262 Multiple jails sharing the same file system can influence each other.
1263 For example, a user in one jail can fill the file system,
1264 leaving no space for processes in the other jail.
1267 to prevent this will not work either, as the file system quotas
1268 are not aware of jails but only look at the user and group IDs.
1269 This means the same user ID in two jails share a single file
1271 One would need to use one file system per jail to make this work.
1272 .Ss "Sysctl MIB Entries"
1274 .Va security.jail.jailed
1275 can be used to determine if a process is running inside a jail (value
1276 is one) or not (value is zero).
1279 .Va security.jail.jail_max_af_ips
1280 determines how may address per address family a jail may have.
1283 Some MIB variables have per-jail settings.
1284 Changes to these variables by a jailed process do not affect the host
1285 environment, only the jail environment.
1287 .Va kern.securelevel ,
1288 .Va security.bsd.suser_enabled ,
1290 .Va kern.domainname ,
1294 .Ss "Hierarchical Jails"
1297 parameter, processes within a jail may be able to create jails of their own.
1298 These child jails are kept in a hierarchy, with jails only able to see and/or
1299 modify the jails they created (or those jails' children).
1300 Each jail has a read-only
1302 parameter, containing the
1304 of the jail that created it; a
1306 of 0 indicates the jail is a child of the current jail (or is a top-level
1307 jail if the current process isn't jailed).
1309 Jailed processes are not allowed to confer greater permissions than they
1310 themselves are given, e.g., if a jail is created with
1312 it is not able to create a jail with
1315 Similarly, such restrictions as
1319 may not be bypassed in child jails.
1321 A child jail may in turn create its own child jails if its own
1323 parameter is set (remember it is zero by default).
1324 These jails are visible to and can be modified by their parent and all
1327 Jail names reflect this hierarchy, with a full name being an MIB-type string
1329 For example, if a base system process creates a jail
1331 and a process under that jail creates another jail
1333 then the second jail will be seen as
1335 in the base system (though it is only seen as
1337 to any processes inside jail
1339 Jids on the other hand exist in a single space, and each jail must have a
1342 Like the names, a child jail's
1344 appears relative to its creator's own
1346 This is by virtue of the child jail being created in the chrooted
1347 environment of the first jail.
1387 Hierarchical/extensible jails were introduced in
1389 The configuration file was introduced in
1393 The jail feature was written by
1394 .An Poul-Henning Kamp
1396 who contributed it to
1400 wrote the extended documentation, found a few bugs, added
1401 a few new features, and cleaned up the userland jail environment.
1404 added multi-IP jail support for IPv4 and IPv6 based on a patch
1406 .An Pawel Jakub Dawidek
1410 added the extensible jail parameters, hierarchical jails,
1411 and the configuration file.
1413 It might be a good idea to add an
1414 address alias flag such that daemons listening on all IPs
1416 will not bind on that address, which would facilitate building a safe
1417 host environment such that host daemons do not impose on services offered
1419 Currently, the simplest answer is to minimize services
1420 offered on the host, possibly limiting it to services offered from
1422 which is easily configurable.
1424 Great care should be taken when managing directories visible within the jail.
1425 For example, if a jailed process has its current working directory set to a
1426 directory that is moved out of the jail's chroot, then the process may gain
1427 access to the file space outside of the jail.
1428 It is recommended that directories always be copied, rather than moved, out
1431 In addition, there are several ways in which an unprivileged user
1432 outside the jail can cooperate with a privileged user inside the jail
1433 and thereby obtain elevated privileges in the host environment.
1434 Most of these attacks can be mitigated by ensuring that the jail root
1435 is not accessible to unprivileged users in the host environment.
1436 Regardless, as a general rule, untrusted users with privileged access
1437 to a jail should not be given access to the host environment.