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2 .\" Copyright (c) 2008-2012 James Gritton
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31 .Nd "manage system jails"
33 .Ss From Configuration File
45 .Op Cm * | Ar jail ...
46 .Ss Without Configuration File
53 .Ar param Ns = Ns Ar value ...
54 .Op Cm command Ns = Ns Ar command ...
58 .Op Cm * | Ar jail ...
64 .Ss Backward Compatibility
71 .Op Fl s Ar securelevel
72 .Ar path hostname ip Ns Op Cm \&, Ns Ar ...
77 utility creates new jails, or modifies or removes existing jails.
78 It can also print a list of configured jails and their parameters.
81 is specified via parameters on the command line, or in the
85 At least one of the options
92 These options are used alone or in combination to describe the operation to
94 .Bl -tag -width indent
101 parameters (if specified on the command line)
102 must not refer to an existing jail.
103 .It Fl e Ar separator
104 Exhibit a list of all configured non-wildcard jails and their parameters.
105 No jail creation, modification or removal performed if this option is used.
108 string is used to separate parameters.
111 utility to list running jails.
113 Modify an existing jail.
118 parameters must exist and refer to an existing jail.
119 Some parameters may not be changed on a running jail.
123 specified by jid or name.
124 All jailed processes are killed, and all jails that are
125 children of this jail are also
128 Restart an existing jail.
129 The jail is first removed and then re-created, as if
133 were run in succession.
135 Create a jail if it does not exist, or modify the jail if it does exist.
137 Modify an existing jail.
138 The jail may be restarted if necessary to modify parameters than could
139 not otherwise be changed.
141 Create a jail if it doesn't exist, or modify (and possibly restart) the
142 jail if it does exist.
145 Other available options are:
146 .Bl -tag -width indent
147 .It Fl f Ar conf_file
148 Use configuration file
150 instead of the default
157 and add all IP addresses returned by the resolver
158 to the list of addresses for this jail.
159 This is equivalent to the
163 Output (only) the jail identifier of the newly created jail(s).
170 file, containing the parameters used to start the jail.
172 Run commands in a clean environment.
173 This is deprecated and is equivalent to the exec.clean parameter.
176 This is deprecated and is equivalent to the
180 Limit the number of commands from
182 that can run simultaneously.
184 Suppress the message printed whenever a jail is created, modified or removed.
185 Only error messages will be printed.
189 option that removes an existing jail without using the configuration file.
190 No removal-related parameters for this jail will be used \(em the jail will
192 .It Fl s Ar securelevel
195 MIB entry to the specified value inside the newly created jail.
196 This is deprecated and is equivalent to the
200 The user name from host environment as whom jailed commands should run.
201 This is deprecated and is equivalent to the
204 .Va exec.system_jail_user
207 The user name from the jailed environment as whom jailed commands should run.
208 This is deprecated and is equivalent to the
212 Print a message on every operation, such as running commands and
213 mounting filesystems.
215 This is deprecated and is equivalent to the
217 parameter, which is also deprecated.
218 It used to allow making changes to a
221 Now such jails are always replaced when a new jail is created with the same
227 If no arguments are given after the options, the operation (except
228 remove) will be performed on all jails specified in the
231 A single argument of a jail name will operate only on the specified jail.
236 options can also remove running jails that aren't in the
238 file, specified by name or jid.
242 is a wildcard that will operate on all jails, regardless of whether
245 this is the surest way for
248 If hierarchical jails exist, a partial-matching wildcard definition may
250 For example, an argument of
252 would apply to jails with names like
257 A jail may also be specified via parameters directly on the command line in
259 form, ignoring the contents of
261 For backward compatibility, the command line may also have four fixed
262 parameters, without names:
271 file, or on the command line, are generally of the form
273 Some parameters are boolean, and do not have a value but are set by the
274 name alone with or without a
280 They can also be given the values
284 Other parameters may have more than one value, specified as a
285 comma-separated list or with
287 in the configuration file (see
293 utility recognizes two classes of parameters.
294 There are the true jail
295 parameters that are passed to the kernel when the jail is created,
296 which can be seen with
298 and can (usually) be changed with
300 Then there are pseudo-parameters that are only used by
304 Jails have a set of core parameters, and kernel modules can add their own
306 The current set of available parameters can be retrieved via
307 .Dq Nm sysctl Fl d Va security.jail.param .
308 Any parameters not set will be given default values, often based on the
310 The core parameters are:
311 .Bl -tag -width indent
314 This will be assigned automatically to a new jail (or can be explicitly
315 set), and can be used to identify the jail for later modification, or
322 This is an arbitrary string that identifies a jail (except it may not
327 it can be passed to later
335 is supplied, a default is assumed that is the same as the
339 parameter is implied by the
341 file format, and need not be explicitly set when using the configuration
344 The directory which is to be the root of the jail.
345 Any commands run inside the jail, either by
349 are run from this directory.
351 A list of IPv4 addresses assigned to the jail.
352 If this is set, the jail is restricted to using only these addresses.
353 Any attempts to use other addresses fail, and attempts to use wildcard
354 addresses silently use the jailed address instead.
355 For IPv4 the first address given will be used as the source address
356 when source address selection on unbound sockets cannot find a better
358 It is only possible to start multiple jails with the same IP address
359 if none of the jails has more than this single overlapping IP address
362 A boolean option to change the formerly mentioned behaviour and disable
363 IPv4 source address selection for the jail in favour of the primary
364 IPv4 address of the jail.
365 Source address selection is enabled by default for all jails and the
367 setting of a parent jail is not inherited for any child jails.
369 Control the availability of IPv4 addresses.
372 to allow unrestricted access to all system addresses,
374 to restrict addresses via
378 to stop the jail from using IPv4 entirely.
381 parameter implies a value of
383 .It Va ip6.addr , Va ip6.saddrsel , Va ip6
384 A set of IPv6 options for the jail, the counterparts to
391 Create the jail with its own virtual network stack,
392 with its own network interfaces, addresses, routing table, etc.
393 The kernel must have been compiled with the
395 for this to be available.
398 to use the system network stack, possibly with restricted IP addresses,
401 to create a new network stack.
403 The hostname of the jail.
404 Other similar parameters are
405 .Va host.domainname ,
410 Set the origin of hostname and related information.
413 to use the system information and
415 for the jail to use the information from the above fields.
416 Setting any of the above fields implies a value of
419 The value of the jail's
422 A jail never has a lower securelevel than its parent system, but by
423 setting this parameter it may have a higher one.
424 If the system securelevel is changed, any jail securelevels will be at
427 The number of the devfs ruleset that is enforced for mounting devfs in
429 A value of zero (default) means no ruleset is enforced.
430 Descendant jails inherit the parent jail's devfs ruleset enforcement.
431 Mounting devfs inside a jail is possible only if the
434 .Va allow.mount.devfs
435 permissions are effective and
437 is set to a value lower than 2.
438 Devfs rules and rulesets cannot be viewed or modified from inside a jail.
440 NOTE: It is important that only appropriate device nodes in devfs be
441 exposed to a jail; access to disk devices in the jail may permit processes
442 in the jail to bypass the jail sandboxing by modifying files outside of
446 for information on how to use devfs rules to limit access to entries
447 in the per-jail devfs.
448 A simple devfs ruleset for jails is available as ruleset #4 in
449 .Pa /etc/defaults/devfs.rules .
451 The number of child jails allowed to be created by this jail (or by
452 other jails under this jail).
453 This limit is zero by default, indicating the jail is not allowed to
456 .Sx "Hierarchical Jails"
457 section for more information.
459 The number of descendants of this jail, including its own child jails
460 and any jails created under them.
461 .It Va enforce_statfs
462 This determines what information processes in a jail are able to get
464 It affects the behaviour of the following syscalls:
470 (as well as similar compatibility syscalls).
471 When set to 0, all mount points are available without any restrictions.
472 When set to 1, only mount points below the jail's chroot directory are
474 In addition to that, the path to the jail's chroot directory is removed
475 from the front of their pathnames.
476 When set to 2 (default), above syscalls can operate only on a mount-point
477 where the jail's chroot directory is located.
479 Setting this boolean parameter allows a jail to exist without any
481 Normally, a command is run as part of jail creation, and then the jail
482 is destroyed as its last process exits.
483 A new jail must have either the
489 pseudo-parameter set.
491 The ID of the cpuset associated with this jail (read-only).
493 This is true if the jail is in the process of shutting down (read-only).
497 of the parent of this jail, or zero if this is a top-level jail
500 The string for the jail's
504 The number for the jail's
508 Some restrictions of the jail environment may be set on a per-jail
510 With the exception of
511 .Va allow.set_hostname
513 .Va allow.reserved_ports ,
514 these boolean parameters are off by default.
515 .Bl -tag -width indent
516 .It Va allow.set_hostname
517 The jail's hostname may be changed via
522 A process within the jail has access to System V IPC primitives.
523 This is deprecated in favor of the per-module parameters (see below).
524 When this parameter is set, it is equivalent to setting
531 .It Va allow.raw_sockets
532 The jail root is allowed to create raw sockets.
533 Setting this parameter allows utilities like
537 to operate inside the jail.
538 If this is set, the source IP addresses are enforced to comply
539 with the IP address bound to the jail, regardless of whether or not
542 flag has been set on the socket.
543 Since raw sockets can be used to configure and interact with various
544 network subsystems, extra caution should be used where privileged access
545 to jails is given out to untrusted parties.
547 Normally, privileged users inside a jail are treated as unprivileged by
549 When this parameter is set, such users are treated as privileged, and
550 may manipulate system file flags subject to the usual constraints on
551 .Va kern.securelevel .
553 privileged users inside the jail will be able to mount and unmount file
554 system types marked as jail-friendly.
557 command can be used to find file system types available for mount from
559 This permission is effective only if
561 is set to a value lower than 2.
562 .It Va allow.mount.devfs
563 privileged users inside the jail will be able to mount and unmount the
565 This permission is effective only together with
569 is set to a value lower than 2.
570 The devfs ruleset should be restricted from the default by using the
574 The jail root may administer quotas on the jail's filesystem(s).
575 This includes filesystems that the jail may share with other jails or
576 with non-jailed parts of the system.
577 .It Va allow.read_msgbuf
578 Jailed users may read the kernel message buffer.
580 .Va security.bsd.unprivileged_read_msgbuf
581 MIB entry is zero, this will be restricted to the root user.
582 .It Va allow.socket_af
583 Sockets within a jail are normally restricted to IPv4, IPv6, local
585 This allows access to other protocol stacks that have not had jail
586 functionality added to them.
588 Locking or unlocking physical pages in memory are normally not available
590 When this parameter is set, users may
595 .Va security.bsd.unprivileged_mlock
605 daemons are permitted to run inside a properly configured vnet-enabled jail.
606 The jail's root must be a file system mount point and
608 must not be set to 0, so that
610 can export file systems visible within the jail.
612 must be set to 1 if file systems mounted under the
613 jail's file system need to be exported by
615 For exporting only the jail's file system, a setting of 2
617 If the kernel configuration does not include the
621 must be loaded outside of the jails.
622 This is normally done by adding
628 file outside of the jails.
631 is to be run in a jail, either the kernel
633 option needs to be specified or
641 file outside of the jails.
642 .It Va allow.reserved_ports
643 The jail root may bind to ports lower than 1024.
644 .It Va allow.unprivileged_proc_debug
645 Unprivileged processes in the jail may use debugging facilities.
647 The value of the jail's
648 .Va security.bsd.suser_enabled
650 The super-user will be disabled automatically if its parent system has it
652 The super-user is enabled by default.
654 Allow privileged process in the jail to manipulate filesystem extended
655 attributes in the system namespace.
659 Kernel modules may add their own parameters, which only exist when the
661 These are typically headed under a parameter named after the module,
664 to give the jail full use of the module,
666 to encapsulate the jail in some module-specific way,
669 to make the module unavailable to the jail.
670 There also may be other parameters to define jail behavior within the module.
671 Module-specific parameters include:
672 .Bl -tag -width indent
673 .It Va allow.mount.fdescfs
674 privileged users inside the jail will be able to mount and unmount the
676 This permission is effective only together with
680 is set to a value lower than 2.
681 .It Va allow.mount.fusefs
682 privileged users inside the jail will be able to mount and unmount
683 fuse-based file systems.
684 This permission is effective only together with
688 is set to a value lower than 2.
689 .It Va allow.mount.nullfs
690 privileged users inside the jail will be able to mount and unmount the
692 This permission is effective only together with
696 is set to a value lower than 2.
697 .It Va allow.mount.procfs
698 privileged users inside the jail will be able to mount and unmount the
700 This permission is effective only together with
704 is set to a value lower than 2.
705 .It Va allow.mount.linprocfs
706 privileged users inside the jail will be able to mount and unmount the
707 linprocfs file system.
708 This permission is effective only together with
712 is set to a value lower than 2.
713 .It Va allow.mount.linsysfs
714 privileged users inside the jail will be able to mount and unmount the
715 linsysfs file system.
716 This permission is effective only together with
720 is set to a value lower than 2.
721 .It Va allow.mount.tmpfs
722 privileged users inside the jail will be able to mount and unmount the
724 This permission is effective only together with
728 is set to a value lower than 2.
729 .It Va allow.mount.zfs
730 privileged users inside the jail will be able to mount and unmount the
732 This permission is effective only together with
736 is set to a value lower than 2.
739 for information on how to configure the ZFS filesystem to operate from
744 This flag is only available when the
746 kernel module is loaded.
748 Determine how a jail's Linux emulation environment appears.
751 will keep the same environment, and
753 will give the jail its own environment (still originally inherited when
754 the jail is created).
755 .It Va linux.osname , linux.osrelease , linux.oss_version
756 The Linux OS name, OS release, and OSS version associated with this jail.
758 Allow access to SYSV IPC message primitives.
761 all IPC objects on the system are visible to this jail, whether they
762 were created by the jail itself, the base system, or other jails.
765 the jail will have its own key namespace, and can only see the objects
767 the system (or parent jail) has access to the jail's objects, but not to
771 the jail cannot perform any sysvmsg-related system calls.
772 .It Va sysvsem, sysvshm
773 Allow access to SYSV IPC semaphore and shared memory primitives, in the
778 There are pseudo-parameters that are not passed to the kernel, but are
781 to set up the jail environment, often by running specified commands
782 when jails are created or removed.
785 command parameters are
787 command lines that are run in either the system or jail environment.
788 They may be given multiple values, which would run the specified
789 commands in sequence.
790 All commands must succeed (return a zero exit status), or the jail will
791 not be created or removed, as appropriate.
793 The pseudo-parameters are:
794 .Bl -tag -width indent
796 Command(s) to run in the system environment to prepare a jail for creation.
797 These commands are executed before assigning IP addresses and mounting
798 filesystems, so they may be used to create a new jail filesystem if it does
801 Command(s) to run in the system environment before a jail is created.
803 Command(s) to run in the system environment right after a jail has been
804 created, but before commands (or services) get executed in the jail.
806 Command(s) to run in the jail environment when a jail is created.
807 A typical command to run is
812 for use when specifying a jail directly on the command line.
813 Unlike other parameters whose value is a single string,
815 uses the remainder of the
817 command line as its own arguments.
818 .It Va exec.poststart
819 Command(s) to run in the system environment after a jail is created,
822 commands have completed.
824 Command(s) to run in the system environment before a jail is removed.
826 Command(s) to run in the jail environment before a jail is removed,
829 commands have completed.
830 A typical command to run is
831 .Dq sh /etc/rc.shutdown jail .
833 Command(s) to run in the system environment after a jail is removed.
835 Command(s) to run in the system environment after all other actions are done.
836 These commands are executed after unmounting filesystems and removing IP
837 addresses, so they may be used to remove a jail filesystem if it is no longer
840 Run commands in a clean environment.
841 The environment is discarded except for
842 .Ev HOME , SHELL , TERM
848 are set to the target login's default values.
850 is set to the target login.
852 is imported from the current environment.
853 The environment variables from the login class capability database for the
854 target login are also set.
855 .It Va exec.jail_user
856 The user to run commands as, when running in the jail environment.
857 The default is to run the commands as the current user.
858 .It Va exec.system_jail_user
859 This boolean option looks for the
863 file, instead of in the jail's file.
864 .It Va exec.system_user
865 The user to run commands as, when running in the system environment.
866 The default is to run the commands as the current user.
868 The maximum amount of time to wait for a command to complete, in
870 If a command is still running after this timeout has passed,
871 the jail will not be created or removed, as appropriate.
872 .It Va exec.consolelog
873 A file to direct command output (stdout and stderr) to.
875 The FIB (routing table) to set when running commands inside the jail.
877 The maximum amount of time to wait for a jail's processes to exit
880 signal (which happens after the
882 commands have completed).
883 After this many seconds have passed, the jail will be removed, which
884 will kill any remaining processes.
885 If this is set to zero, no
887 is sent and the jail is immediately removed.
888 The default is 10 seconds.
890 A network interface to add the jail's IP addresses
895 An alias for each address will be added to the interface before the
896 jail is created, and will be removed from the interface after the
899 In addition to the IP addresses that are passed to the kernel, an
900 interface, netmask and additional parameters (as supported by
902 may also be specified, in the form
903 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
904 If an interface is given before the IP address, an alias for the address
905 will be added to that interface, as it is with the
908 If a netmask in either dotted-quad or CIDR form is given
909 after an IP address, it will be used when adding the IP alias.
910 If additional parameters are specified then they will also be used when
913 In addition to the IP addresses that are passed to the kernel,
914 an interface, prefix and additional parameters (as supported by
916 may also be specified, in the form
917 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
918 .It Va vnet.interface
919 A network interface to give to a vnet-enabled jail after is it created.
920 The interface will automatically be released when the jail is removed.
924 parameter and add all IP addresses returned by the resolver
925 to the list of addresses
930 This may affect default address selection for outgoing IPv4 connections
932 The address first returned by the resolver for each address family
933 will be used as the primary address.
935 A filesystem to mount before creating the jail (and to unmount after
936 removing it), given as a single
942 format file containing filesystems to mount before creating a jail.
946 filesystem on the chrooted
948 directory, and apply the ruleset in the
950 parameter (or a default of ruleset 4: devfsrules_jail)
951 to restrict the devices visible inside the jail.
955 filesystem on the chrooted
961 filesystem on the chrooted
965 This is deprecated and has no effect.
966 It used to allow making changes to a
969 Now such jails are always replaced when a new jail is created with the same
974 Specify a jail (or jails) that this jail depends on.
975 When this jail is to be created, any jail(s) it depends on must already exist.
976 If not, they will be created automatically, up to the completion of the last
978 command, before any action will taken to create this jail.
979 When jails are removed the opposite is true:
980 this jail will be removed, up to the last
982 command, before any jail(s) it depends on are stopped.
985 Jails are typically set up using one of two philosophies: either to
986 constrain a specific application (possibly running with privilege), or
988 .Dq "virtual system image"
989 running a variety of daemons and services.
990 In both cases, a fairly complete file system install of
993 required, so as to provide the necessary command line tools, daemons,
994 libraries, application configuration files, etc.
995 However, for a virtual server configuration, a fair amount of
996 additional work is required so as to replace the
999 This manual page documents the configuration steps necessary to support
1000 either of these steps, although the configuration steps may need to be
1001 refined based on local requirements.
1002 .Ss "Setting up a Jail Directory Tree"
1003 To set up a jail directory tree containing an entire
1005 distribution, the following
1007 command script can be used:
1008 .Bd -literal -offset indent
1012 make world DESTDIR=$D
1013 make distribution DESTDIR=$D
1016 In many cases this example would put far more in the jail than needed.
1017 In the other extreme case a jail might contain only one file:
1018 the executable to be run in the jail.
1020 We recommend experimentation, and caution that it is a lot easier to
1023 jail and remove things until it stops working,
1024 than it is to start with a
1026 jail and add things until it works.
1027 .Ss "Setting Up a Jail"
1028 Do what was described in
1029 .Sx "Setting Up a Jail Directory Tree"
1030 to build the jail directory tree.
1031 For the sake of this example, we will
1032 assume you built it in
1033 .Pa /data/jail/testjail ,
1036 Substitute below as needed with your
1037 own directory, IP address, and hostname.
1038 .Ss "Setting up the Host Environment"
1039 First, set up the real system's environment to be
1041 For consistency, we will refer to the parent box as the
1042 .Dq "host environment" ,
1043 and to the jailed virtual machine as the
1044 .Dq "jail environment" .
1045 Since jails are implemented using IP aliases, one of the first things to do
1046 is to disable IP services on the host system that listen on all local
1047 IP addresses for a service.
1048 If a network service is present in the host environment that binds all
1049 available IP addresses rather than specific IP addresses, it may service
1050 requests sent to jail IP addresses if the jail did not bind the port.
1053 to only listen on the
1054 appropriate IP address, and so forth.
1055 Add the following to
1057 in the host environment:
1058 .Bd -literal -offset indent
1059 sendmail_enable="NO"
1060 inetd_flags="-wW -a 192.0.2.23"
1065 is the native IP address for the host system, in this example.
1066 Daemons that run out of
1068 can be easily configured to use only the specified host IP address.
1070 will need to be manually configured \(em for some this is possible through
1072 flags entries; for others it is necessary to modify per-application
1073 configuration files, or to recompile the application.
1074 The following frequently deployed services must have their individual
1075 configuration files modified to limit the application to listening
1076 to a specific IP address:
1080 it is necessary to modify
1081 .Pa /etc/ssh/sshd_config .
1085 it is necessary to modify
1086 .Pa /etc/mail/sendmail.cf .
1088 In addition, a number of services must be recompiled in order to run
1089 them in the host environment.
1090 This includes most applications providing services using
1097 In general, applications for which it is not possible to specify which
1098 IP address to bind should not be run in the host environment unless they
1099 should also service requests sent to jail IP addresses.
1101 NFS from the host environment may also cause confusion, and cannot be
1102 easily reconfigured to use only specific IPs, as some NFS services are
1103 hosted directly from the kernel.
1104 Any third-party network software running
1105 in the host environment should also be checked and configured so that it
1106 does not bind all IP addresses, which would result in those services also
1107 appearing to be offered by the jail environments.
1110 these daemons have been disabled or fixed in the host environment, it is
1111 best to reboot so that all daemons are in a known state, to reduce the
1112 potential for confusion later (such as finding that when you send mail
1113 to a jail, and its sendmail is down, the mail is delivered to the host,
1115 .Ss "Configuring the Jail"
1116 Start any jail for the first time without configuring the network
1117 interface so that you can clean it up a little and set up accounts.
1119 with any machine (virtual or not), you will need to set a root password, time
1121 Some of these steps apply only if you intend to run a full virtual server
1122 inside the jail; others apply both for constraining a particular application
1123 or for running a virtual server.
1125 Start a shell in the jail:
1126 .Bd -literal -offset indent
1127 jail -c path=/data/jail/testjail mount.devfs \\
1128 host.hostname=testhostname ip4.addr=192.0.2.100 \\
1132 Assuming no errors, you will end up with a shell prompt within the jail.
1135 and do the post-install configuration to set various configuration options,
1136 or perform these actions manually by editing
1140 .Bl -bullet -offset indent -compact
1143 .Pa /etc/resolv.conf
1144 so that name resolution within the jail will work correctly.
1152 Set a root password, probably different from the real host system.
1156 Add accounts for users in the jail environment.
1158 Install any packages the environment requires.
1161 You may also want to perform any package-specific configuration (web servers,
1162 SSH servers, etc), patch up
1163 .Pa /etc/syslog.conf
1164 so it logs as you would like, etc.
1165 If you are not using a virtual server, you may wish to modify
1167 in the host environment to listen on the syslog socket in the jail
1168 environment; in this example, the syslog socket would be stored in
1169 .Pa /data/jail/testjail/var/run/log .
1171 Exit from the shell, and the jail will be shut down.
1172 .Ss "Starting the Jail"
1173 You are now ready to restart the jail and bring up the environment with
1174 all of its daemons and other programs.
1175 Create an entry for the jail in
1176 .Pa /etc/jail.conf :
1177 .Bd -literal -offset indent
1179 path = /tmp/jail/testjail;
1181 host.hostname = testhostname;
1182 ip4.addr = 192.0.2.100;
1184 exec.start = "/bin/sh /etc/rc";
1185 exec.stop = "/bin/sh /etc/rc.shutdown jail";
1189 To start a virtual server environment,
1191 is run to launch various daemons and services, and
1192 .Pa /etc/rc.shutdown
1193 is run to shut them down when the jail is removed.
1194 If you are running a single application in the jail,
1195 substitute the command used to start the application for
1196 .Dq /bin/sh /etc/rc ;
1197 there may be some script available to cleanly shut down the application,
1198 or it may be sufficient to go without a stop command, and have
1204 Start the jail by running:
1205 .Bd -literal -offset indent
1209 A few warnings may be produced; however, it should all work properly.
1210 You should be able to see
1213 and other processes running within the jail using
1217 flag appearing beside jailed processes.
1218 To see an active list of jails, use
1222 is enabled in the jail environment, you should be able to
1224 to the hostname or IP address of the jailed environment, and log
1225 in using the accounts you created previously.
1227 It is possible to have jails started at boot time.
1232 for more information.
1233 .Ss "Managing the Jail"
1234 Normal machine shutdown commands, such as
1239 cannot be used successfully within the jail.
1240 To kill all processes from within a jail, you may use one of the
1241 following commands, depending on what you want to accomplish:
1242 .Bd -literal -offset indent
1251 signals to all processes in the jail \(em be careful not to run this from
1252 the host environment!
1253 Once all of the jail's processes have died, unless the jail was created
1256 parameter, the jail will be removed.
1258 the intended use of the jail, you may also want to run
1259 .Pa /etc/rc.shutdown
1260 from within the jail.
1262 To shut down the jail from the outside, simply remove it with:
1263 .Bd -literal -offset indent
1267 which will run any commands specified by
1273 to any remaining jailed processes.
1276 .Pa /proc/ Ns Ar pid Ns Pa /status
1277 file contains, as its last field, the name of the jail in which the
1280 to indicate that the process is not running within a jail.
1283 command also shows a
1285 flag for processes in a jail.
1287 You can also list/kill processes based on their jail ID.
1288 To show processes and their jail ID, use the following command:
1290 .Dl "ps ax -o pid,jid,args"
1292 To show and then kill processes in jail number 3 use the following commands:
1293 .Bd -literal -offset indent
1300 .Ss "Jails and File Systems"
1301 It is not possible to
1305 any file system inside a jail unless the file system is marked
1306 jail-friendly, the jail's
1308 parameter is set, and the jail's
1310 parameter is lower than 2.
1312 Multiple jails sharing the same file system can influence each other.
1313 For example, a user in one jail can fill the file system,
1314 leaving no space for processes in the other jail.
1317 to prevent this will not work either, as the file system quotas
1318 are not aware of jails but only look at the user and group IDs.
1319 This means the same user ID in two jails share a single file
1321 One would need to use one file system per jail to make this work.
1322 .Ss "Sysctl MIB Entries"
1324 .Va security.jail.jailed
1325 can be used to determine if a process is running inside a jail (value
1326 is one) or not (value is zero).
1329 .Va security.jail.jail_max_af_ips
1330 determines how may address per address family a jail may have.
1333 Some MIB variables have per-jail settings.
1334 Changes to these variables by a jailed process do not affect the host
1335 environment, only the jail environment.
1337 .Va kern.securelevel ,
1338 .Va security.bsd.suser_enabled ,
1340 .Va kern.domainname ,
1344 .Ss "Hierarchical Jails"
1347 parameter, processes within a jail may be able to create jails of their own.
1348 These child jails are kept in a hierarchy, with jails only able to see and/or
1349 modify the jails they created (or those jails' children).
1350 Each jail has a read-only
1352 parameter, containing the
1354 of the jail that created it; a
1356 of 0 indicates the jail is a child of the current jail (or is a top-level
1357 jail if the current process isn't jailed).
1359 Jailed processes are not allowed to confer greater permissions than they
1360 themselves are given, e.g., if a jail is created with
1362 it is not able to create a jail with
1365 Similarly, such restrictions as
1369 may not be bypassed in child jails.
1371 A child jail may in turn create its own child jails if its own
1373 parameter is set (remember it is zero by default).
1374 These jails are visible to and can be modified by their parent and all
1377 Jail names reflect this hierarchy, with a full name being an MIB-type string
1379 For example, if a base system process creates a jail
1381 and a process under that jail creates another jail
1383 then the second jail will be seen as
1385 in the base system (though it is only seen as
1387 to any processes inside jail
1389 Jids on the other hand exist in a single space, and each jail must have a
1392 Like the names, a child jail's
1394 appears relative to its creator's own
1396 This is by virtue of the child jail being created in the chrooted
1397 environment of the first jail.
1440 Hierarchical/extensible jails were introduced in
1442 The configuration file was introduced in
1446 The jail feature was written by
1447 .An Poul-Henning Kamp
1449 who contributed it to
1453 wrote the extended documentation, found a few bugs, added
1454 a few new features, and cleaned up the userland jail environment.
1457 added multi-IP jail support for IPv4 and IPv6 based on a patch
1459 .An Pawel Jakub Dawidek
1463 added the extensible jail parameters, hierarchical jails,
1464 and the configuration file.
1466 It might be a good idea to add an
1467 address alias flag such that daemons listening on all IPs
1469 will not bind on that address, which would facilitate building a safe
1470 host environment such that host daemons do not impose on services offered
1472 Currently, the simplest answer is to minimize services
1473 offered on the host, possibly limiting it to services offered from
1475 which is easily configurable.
1477 Great care should be taken when managing directories visible within the jail.
1478 For example, if a jailed process has its current working directory set to a
1479 directory that is moved out of the jail's chroot, then the process may gain
1480 access to the file space outside of the jail.
1481 It is recommended that directories always be copied, rather than moved, out
1484 In addition, there are several ways in which an unprivileged user
1485 outside the jail can cooperate with a privileged user inside the jail
1486 and thereby obtain elevated privileges in the host environment.
1487 Most of these attacks can be mitigated by ensuring that the jail root
1488 is not accessible to unprivileged users in the host environment.
1489 Regardless, as a general rule, untrusted users with privileged access
1490 to a jail should not be given access to the host environment.