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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
148 Allow making changes to a dying jail, equivalent to the
151 .It Fl f Ar conf_file
152 Use configuration file
154 instead of the default
161 and add all IP addresses returned by the resolver
162 to the list of addresses for this jail.
163 This is equivalent to the
167 Output (only) the jail identifier of the newly created jail(s).
174 file, containing the parameters used to start the jail.
176 Run commands in a clean environment.
177 This is deprecated and is equivalent to the exec.clean parameter.
180 This is deprecated and is equivalent to the
184 Limit the number of commands from
186 that can run simultaneously.
188 Suppress the message printed whenever a jail is created, modified or removed.
189 Only error messages will be printed.
193 option that removes an existing jail without using the configuration file.
194 No removal-related parameters for this jail will be used \(em the jail will
196 .It Fl s Ar securelevel
199 MIB entry to the specified value inside the newly created jail.
200 This is deprecated and is equivalent to the
204 The user name from host environment as whom jailed commands should run.
205 This is deprecated and is equivalent to the
208 .Va exec.system_jail_user
211 The user name from the jailed environment as whom jailed commands should run.
212 This is deprecated and is equivalent to the
216 Print a message on every operation, such as running commands and
217 mounting filesystems.
220 If no arguments are given after the options, the operation (except
221 remove) will be performed on all jails specified in the
224 A single argument of a jail name will operate only on the specified jail.
229 options can also remove running jails that aren't in the
231 file, specified by name or jid.
235 is a wildcard that will operate on all jails, regardless of whether
238 this is the surest way for
241 If hierarchical jails exist, a partial-matching wildcard definition may
243 For example, an argument of
245 would apply to jails with names like
250 A jail may also be specified via parameters directly on the command line in
252 form, ignoring the contents of
254 For backward compatibility, the command line may also have four fixed
255 parameters, without names:
264 file, or on the command line, are generally of the form
266 Some parameters are boolean, and do not have a value but are set by the
267 name alone with or without a
273 They can also be given the values
277 Other parameters may have more than one value, specified as a
278 comma-separated list or with
280 in the configuration file (see
286 utility recognizes two classes of parameters.
287 There are the true jail
288 parameters that are passed to the kernel when the jail is created,
289 which can be seen with
291 and can (usually) be changed with
293 Then there are pseudo-parameters that are only used by
297 Jails have a set of core parameters, and kernel modules can add their own
299 The current set of available parameters can be retrieved via
300 .Dq Nm sysctl Fl d Va security.jail.param .
301 Any parameters not set will be given default values, often based on the
303 The core parameters are:
304 .Bl -tag -width indent
307 This will be assigned automatically to a new jail (or can be explicitly
308 set), and can be used to identify the jail for later modification, or
315 This is an arbitrary string that identifies a jail (except it may not
320 it can be passed to later
328 is supplied, a default is assumed that is the same as the
332 parameter is implied by the
334 file format, and need not be explicitly set when using the configuration
337 The directory which is to be the root of the jail.
338 Any commands run inside the jail, either by
342 are run from this directory.
344 A list of IPv4 addresses assigned to the jail.
345 If this is set, the jail is restricted to using only these addresses.
346 Any attempts to use other addresses fail, and attempts to use wildcard
347 addresses silently use the jailed address instead.
348 For IPv4 the first address given will be used as the source address
349 when source address selection on unbound sockets cannot find a better
351 It is only possible to start multiple jails with the same IP address
352 if none of the jails has more than this single overlapping IP address
355 A boolean option to change the formerly mentioned behaviour and disable
356 IPv4 source address selection for the jail in favour of the primary
357 IPv4 address of the jail.
358 Source address selection is enabled by default for all jails and the
360 setting of a parent jail is not inherited for any child jails.
362 Control the availability of IPv4 addresses.
365 to allow unrestricted access to all system addresses,
367 to restrict addresses via
371 to stop the jail from using IPv4 entirely.
374 parameter implies a value of
376 .It Va ip6.addr , Va ip6.saddrsel , Va ip6
377 A set of IPv6 options for the jail, the counterparts to
384 Create the jail with its own virtual network stack,
385 with its own network interfaces, addresses, routing table, etc.
386 The kernel must have been compiled with the
388 for this to be available.
391 to use the system network stack, possibly with restricted IP addresses,
394 to create a new network stack.
396 The hostname of the jail.
397 Other similar parameters are
398 .Va host.domainname ,
403 Set the origin of hostname and related information.
406 to use the system information and
408 for the jail to use the information from the above fields.
409 Setting any of the above fields implies a value of
412 The value of the jail's
415 A jail never has a lower securelevel than its parent system, but by
416 setting this parameter it may have a higher one.
417 If the system securelevel is changed, any jail securelevels will be at
420 The number of the devfs ruleset that is enforced for mounting devfs in
422 A value of zero (default) means no ruleset is enforced.
423 Descendant jails inherit the parent jail's devfs ruleset enforcement.
424 Mounting devfs inside a jail is possible only if the
427 .Va allow.mount.devfs
428 permissions are effective and
430 is set to a value lower than 2.
431 Devfs rules and rulesets cannot be viewed or modified from inside a jail.
433 NOTE: It is important that only appropriate device nodes in devfs be
434 exposed to a jail; access to disk devices in the jail may permit processes
435 in the jail to bypass the jail sandboxing by modifying files outside of
439 for information on how to use devfs rules to limit access to entries
440 in the per-jail devfs.
441 A simple devfs ruleset for jails is available as ruleset #4 in
442 .Pa /etc/defaults/devfs.rules .
444 The number of child jails allowed to be created by this jail (or by
445 other jails under this jail).
446 This limit is zero by default, indicating the jail is not allowed to
449 .Sx "Hierarchical Jails"
450 section for more information.
452 The number of descendants of this jail, including its own child jails
453 and any jails created under them.
454 .It Va enforce_statfs
455 This determines what information processes in a jail are able to get
457 It affects the behaviour of the following syscalls:
463 (as well as similar compatibility syscalls).
464 When set to 0, all mount points are available without any restrictions.
465 When set to 1, only mount points below the jail's chroot directory are
467 In addition to that, the path to the jail's chroot directory is removed
468 from the front of their pathnames.
469 When set to 2 (default), above syscalls can operate only on a mount-point
470 where the jail's chroot directory is located.
472 Setting this boolean parameter allows a jail to exist without any
474 Normally, a command is run as part of jail creation, and then the jail
475 is destroyed as its last process exits.
476 A new jail must have either the
482 pseudo-parameter set.
484 The ID of the cpuset associated with this jail (read-only).
486 This is true if the jail is in the process of shutting down (read-only).
490 of the parent of this jail, or zero if this is a top-level jail
493 The string for the jail's
497 The number for the jail's
501 Some restrictions of the jail environment may be set on a per-jail
503 With the exception of
504 .Va allow.set_hostname
506 .Va allow.reserved_ports ,
507 these boolean parameters are off by default.
508 .Bl -tag -width indent
509 .It Va allow.set_hostname
510 The jail's hostname may be changed via
515 A process within the jail has access to System V IPC primitives.
516 This is deprecated in favor of the per-module parameters (see below).
517 When this parameter is set, it is equivalent to setting
524 .It Va allow.raw_sockets
525 The jail root is allowed to create raw sockets.
526 Setting this parameter allows utilities like
530 to operate inside the jail.
531 If this is set, the source IP addresses are enforced to comply
532 with the IP address bound to the jail, regardless of whether or not
535 flag has been set on the socket.
536 Since raw sockets can be used to configure and interact with various
537 network subsystems, extra caution should be used where privileged access
538 to jails is given out to untrusted parties.
540 Normally, privileged users inside a jail are treated as unprivileged by
542 When this parameter is set, such users are treated as privileged, and
543 may manipulate system file flags subject to the usual constraints on
544 .Va kern.securelevel .
546 privileged users inside the jail will be able to mount and unmount file
547 system types marked as jail-friendly.
550 command can be used to find file system types available for mount from
552 This permission is effective only if
554 is set to a value lower than 2.
555 .It Va allow.mount.devfs
556 privileged users inside the jail will be able to mount and unmount the
558 This permission is effective only together with
562 is set to a value lower than 2.
563 The devfs ruleset should be restricted from the default by using the
567 The jail root may administer quotas on the jail's filesystem(s).
568 This includes filesystems that the jail may share with other jails or
569 with non-jailed parts of the system.
570 .It Va allow.read_msgbuf
571 Jailed users may read the kernel message buffer.
573 .Va security.bsd.unprivileged_read_msgbuf
574 MIB entry is zero, this will be restricted to the root user.
575 .It Va allow.socket_af
576 Sockets within a jail are normally restricted to IPv4, IPv6, local
578 This allows access to other protocol stacks that have not had jail
579 functionality added to them.
581 Locking or unlocking physical pages in memory are normally not available
583 When this parameter is set, users may
588 .Va security.bsd.unprivileged_mlock
598 daemons are permitted to run inside a properly configured vnet-enabled jail.
599 The jail's root must be a file system mount point and
601 must not be set to 0, so that
603 can export file systems visible within the jail.
605 must be set to 1 if file systems mounted under the
606 jail's file system need to be exported by
608 For exporting only the jail's file system, a setting of 2
610 If the kernel configuration does not include the
614 must be loaded outside of the jails.
615 This is normally done by adding
621 file outside of the jails.
624 is to be run in a jail, either the kernel
626 option needs to be specified or
634 file outside of the jails.
635 .It Va allow.reserved_ports
636 The jail root may bind to ports lower than 1024.
637 .It Va allow.unprivileged_proc_debug
638 Unprivileged processes in the jail may use debugging facilities.
640 The value of the jail's
641 .Va security.bsd.suser_enabled
643 The super-user will be disabled automatically if its parent system has it
645 The super-user is enabled by default.
647 Allow privileged process in the jail to manipulate filesystem extended
648 attributes in the system namespace.
652 Kernel modules may add their own parameters, which only exist when the
654 These are typically headed under a parameter named after the module,
657 to give the jail full use of the module,
659 to encapsulate the jail in some module-specific way,
662 to make the module unavailable to the jail.
663 There also may be other parameters to define jail behavior within the module.
664 Module-specific parameters include:
665 .Bl -tag -width indent
666 .It Va allow.mount.fdescfs
667 privileged users inside the jail will be able to mount and unmount the
669 This permission is effective only together with
673 is set to a value lower than 2.
674 .It Va allow.mount.fusefs
675 privileged users inside the jail will be able to mount and unmount
676 fuse-based file systems.
677 This permission is effective only together with
681 is set to a value lower than 2.
682 .It Va allow.mount.nullfs
683 privileged users inside the jail will be able to mount and unmount the
685 This permission is effective only together with
689 is set to a value lower than 2.
690 .It Va allow.mount.procfs
691 privileged users inside the jail will be able to mount and unmount the
693 This permission is effective only together with
697 is set to a value lower than 2.
698 .It Va allow.mount.linprocfs
699 privileged users inside the jail will be able to mount and unmount the
700 linprocfs file system.
701 This permission is effective only together with
705 is set to a value lower than 2.
706 .It Va allow.mount.linsysfs
707 privileged users inside the jail will be able to mount and unmount the
708 linsysfs file system.
709 This permission is effective only together with
713 is set to a value lower than 2.
714 .It Va allow.mount.tmpfs
715 privileged users inside the jail will be able to mount and unmount the
717 This permission is effective only together with
721 is set to a value lower than 2.
722 .It Va allow.mount.zfs
723 privileged users inside the jail will be able to mount and unmount the
725 This permission is effective only together with
729 is set to a value lower than 2.
732 for information on how to configure the ZFS filesystem to operate from
737 This flag is only available when the
739 kernel module is loaded.
741 Determine how a jail's Linux emulation environment appears.
744 will keep the same environment, and
746 will give the jail its own environment (still originally inherited when
747 the jail is created).
748 .It Va linux.osname , linux.osrelease , linux.oss_version
749 The Linux OS name, OS release, and OSS version associated with this jail.
751 Allow access to SYSV IPC message primitives.
754 all IPC objects on the system are visible to this jail, whether they
755 were created by the jail itself, the base system, or other jails.
758 the jail will have its own key namespace, and can only see the objects
760 the system (or parent jail) has access to the jail's objects, but not to
764 the jail cannot perform any sysvmsg-related system calls.
765 .It Va sysvsem, sysvshm
766 Allow access to SYSV IPC semaphore and shared memory primitives, in the
771 There are pseudo-parameters that are not passed to the kernel, but are
774 to set up the jail environment, often by running specified commands
775 when jails are created or removed.
778 command parameters are
780 command lines that are run in either the system or jail environment.
781 They may be given multiple values, which would run the specified
782 commands in sequence.
783 All commands must succeed (return a zero exit status), or the jail will
784 not be created or removed, as appropriate.
786 The pseudo-parameters are:
787 .Bl -tag -width indent
789 Command(s) to run in the system environment to prepare a jail for creation.
790 These commands are executed before assigning IP addresses and mounting
791 filesystems, so they may be used to create a new jail filesystem if it does
794 Command(s) to run in the system environment before a jail is created.
796 Command(s) to run in the system environment right after a jail has been
797 created, but before commands (or services) get executed in the jail.
799 Command(s) to run in the jail environment when a jail is created.
800 A typical command to run is
805 for use when specifying a jail directly on the command line.
806 Unlike other parameters whose value is a single string,
808 uses the remainder of the
810 command line as its own arguments.
811 .It Va exec.poststart
812 Command(s) to run in the system environment after a jail is created,
815 commands have completed.
817 Command(s) to run in the system environment before a jail is removed.
819 Command(s) to run in the jail environment before a jail is removed,
822 commands have completed.
823 A typical command to run is
824 .Dq sh /etc/rc.shutdown jail .
826 Command(s) to run in the system environment after a jail is removed.
828 Command(s) to run in the system environment after all other actions are done.
829 These commands are executed after unmounting filesystems and removing IP
830 addresses, so they may be used to remove a jail filesystem if it is no longer
833 Run commands in a clean environment.
834 The environment is discarded except for
835 .Ev HOME , SHELL , TERM
841 are set to the target login's default values.
843 is set to the target login.
845 is imported from the current environment.
846 The environment variables from the login class capability database for the
847 target login are also set.
848 .It Va exec.jail_user
849 The user to run commands as, when running in the jail environment.
850 The default is to run the commands as the current user.
851 .It Va exec.system_jail_user
852 This boolean option looks for the
856 file, instead of in the jail's file.
857 .It Va exec.system_user
858 The user to run commands as, when running in the system environment.
859 The default is to run the commands as the current user.
861 The maximum amount of time to wait for a command to complete, in
863 If a command is still running after this timeout has passed,
864 the jail will not be created or removed, as appropriate.
865 .It Va exec.consolelog
866 A file to direct command output (stdout and stderr) to.
868 The FIB (routing table) to set when running commands inside the jail.
870 The maximum amount of time to wait for a jail's processes to exit
873 signal (which happens after the
875 commands have completed).
876 After this many seconds have passed, the jail will be removed, which
877 will kill any remaining processes.
878 If this is set to zero, no
880 is sent and the jail is immediately removed.
881 The default is 10 seconds.
883 A network interface to add the jail's IP addresses
888 An alias for each address will be added to the interface before the
889 jail is created, and will be removed from the interface after the
892 In addition to the IP addresses that are passed to the kernel, an
893 interface, netmask and additional parameters (as supported by
895 may also be specified, in the form
896 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
897 If an interface is given before the IP address, an alias for the address
898 will be added to that interface, as it is with the
901 If a netmask in either dotted-quad or CIDR form is given
902 after an IP address, it will be used when adding the IP alias.
903 If additional parameters are specified then they will also be used when
906 In addition to the IP addresses that are passed to the kernel,
907 an interface, prefix and additional parameters (as supported by
909 may also be specified, in the form
910 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
911 .It Va vnet.interface
912 A network interface to give to a vnet-enabled jail after is it created.
913 The interface will automatically be released when the jail is removed.
917 parameter and add all IP addresses returned by the resolver
918 to the list of addresses
923 This may affect default address selection for outgoing IPv4 connections
925 The address first returned by the resolver for each address family
926 will be used as the primary address.
928 A filesystem to mount before creating the jail (and to unmount after
929 removing it), given as a single
935 format file containing filesystems to mount before creating a jail.
939 filesystem on the chrooted
941 directory, and apply the ruleset in the
943 parameter (or a default of ruleset 4: devfsrules_jail)
944 to restrict the devices visible inside the jail.
948 filesystem on the chrooted
954 filesystem on the chrooted
958 Allow making changes to a
962 Specify a jail (or jails) that this jail depends on.
963 When this jail is to be created, any jail(s) it depends on must already exist.
964 If not, they will be created automatically, up to the completion of the last
966 command, before any action will taken to create this jail.
967 When jails are removed the opposite is true:
968 this jail will be removed, up to the last
970 command, before any jail(s) it depends on are stopped.
973 Jails are typically set up using one of two philosophies: either to
974 constrain a specific application (possibly running with privilege), or
976 .Dq "virtual system image"
977 running a variety of daemons and services.
978 In both cases, a fairly complete file system install of
981 required, so as to provide the necessary command line tools, daemons,
982 libraries, application configuration files, etc.
983 However, for a virtual server configuration, a fair amount of
984 additional work is required so as to replace the
987 This manual page documents the configuration steps necessary to support
988 either of these steps, although the configuration steps may need to be
989 refined based on local requirements.
990 .Ss "Setting up a Jail Directory Tree"
991 To set up a jail directory tree containing an entire
993 distribution, the following
995 command script can be used:
996 .Bd -literal -offset indent
1000 make world DESTDIR=$D
1001 make distribution DESTDIR=$D
1004 In many cases this example would put far more in the jail than needed.
1005 In the other extreme case a jail might contain only one file:
1006 the executable to be run in the jail.
1008 We recommend experimentation, and caution that it is a lot easier to
1011 jail and remove things until it stops working,
1012 than it is to start with a
1014 jail and add things until it works.
1015 .Ss "Setting Up a Jail"
1016 Do what was described in
1017 .Sx "Setting Up a Jail Directory Tree"
1018 to build the jail directory tree.
1019 For the sake of this example, we will
1020 assume you built it in
1021 .Pa /data/jail/testjail ,
1024 Substitute below as needed with your
1025 own directory, IP address, and hostname.
1026 .Ss "Setting up the Host Environment"
1027 First, set up the real system's environment to be
1029 For consistency, we will refer to the parent box as the
1030 .Dq "host environment" ,
1031 and to the jailed virtual machine as the
1032 .Dq "jail environment" .
1033 Since jails are implemented using IP aliases, one of the first things to do
1034 is to disable IP services on the host system that listen on all local
1035 IP addresses for a service.
1036 If a network service is present in the host environment that binds all
1037 available IP addresses rather than specific IP addresses, it may service
1038 requests sent to jail IP addresses if the jail did not bind the port.
1041 to only listen on the
1042 appropriate IP address, and so forth.
1043 Add the following to
1045 in the host environment:
1046 .Bd -literal -offset indent
1047 sendmail_enable="NO"
1048 inetd_flags="-wW -a 192.0.2.23"
1053 is the native IP address for the host system, in this example.
1054 Daemons that run out of
1056 can be easily configured to use only the specified host IP address.
1058 will need to be manually configured \(em for some this is possible through
1060 flags entries; for others it is necessary to modify per-application
1061 configuration files, or to recompile the application.
1062 The following frequently deployed services must have their individual
1063 configuration files modified to limit the application to listening
1064 to a specific IP address:
1068 it is necessary to modify
1069 .Pa /etc/ssh/sshd_config .
1073 it is necessary to modify
1074 .Pa /etc/mail/sendmail.cf .
1076 In addition, a number of services must be recompiled in order to run
1077 them in the host environment.
1078 This includes most applications providing services using
1085 In general, applications for which it is not possible to specify which
1086 IP address to bind should not be run in the host environment unless they
1087 should also service requests sent to jail IP addresses.
1089 NFS from the host environment may also cause confusion, and cannot be
1090 easily reconfigured to use only specific IPs, as some NFS services are
1091 hosted directly from the kernel.
1092 Any third-party network software running
1093 in the host environment should also be checked and configured so that it
1094 does not bind all IP addresses, which would result in those services also
1095 appearing to be offered by the jail environments.
1098 these daemons have been disabled or fixed in the host environment, it is
1099 best to reboot so that all daemons are in a known state, to reduce the
1100 potential for confusion later (such as finding that when you send mail
1101 to a jail, and its sendmail is down, the mail is delivered to the host,
1103 .Ss "Configuring the Jail"
1104 Start any jail for the first time without configuring the network
1105 interface so that you can clean it up a little and set up accounts.
1107 with any machine (virtual or not), you will need to set a root password, time
1109 Some of these steps apply only if you intend to run a full virtual server
1110 inside the jail; others apply both for constraining a particular application
1111 or for running a virtual server.
1113 Start a shell in the jail:
1114 .Bd -literal -offset indent
1115 jail -c path=/data/jail/testjail mount.devfs \\
1116 host.hostname=testhostname ip4.addr=192.0.2.100 \\
1120 Assuming no errors, you will end up with a shell prompt within the jail.
1123 and do the post-install configuration to set various configuration options,
1124 or perform these actions manually by editing
1128 .Bl -bullet -offset indent -compact
1131 .Pa /etc/resolv.conf
1132 so that name resolution within the jail will work correctly.
1140 Set a root password, probably different from the real host system.
1144 Add accounts for users in the jail environment.
1146 Install any packages the environment requires.
1149 You may also want to perform any package-specific configuration (web servers,
1150 SSH servers, etc), patch up
1151 .Pa /etc/syslog.conf
1152 so it logs as you would like, etc.
1153 If you are not using a virtual server, you may wish to modify
1155 in the host environment to listen on the syslog socket in the jail
1156 environment; in this example, the syslog socket would be stored in
1157 .Pa /data/jail/testjail/var/run/log .
1159 Exit from the shell, and the jail will be shut down.
1160 .Ss "Starting the Jail"
1161 You are now ready to restart the jail and bring up the environment with
1162 all of its daemons and other programs.
1163 Create an entry for the jail in
1164 .Pa /etc/jail.conf :
1165 .Bd -literal -offset indent
1167 path = /tmp/jail/testjail;
1169 host.hostname = testhostname;
1170 ip4.addr = 192.0.2.100;
1172 exec.start = "/bin/sh /etc/rc";
1173 exec.stop = "/bin/sh /etc/rc.shutdown jail";
1177 To start a virtual server environment,
1179 is run to launch various daemons and services, and
1180 .Pa /etc/rc.shutdown
1181 is run to shut them down when the jail is removed.
1182 If you are running a single application in the jail,
1183 substitute the command used to start the application for
1184 .Dq /bin/sh /etc/rc ;
1185 there may be some script available to cleanly shut down the application,
1186 or it may be sufficient to go without a stop command, and have
1192 Start the jail by running:
1193 .Bd -literal -offset indent
1197 A few warnings may be produced; however, it should all work properly.
1198 You should be able to see
1201 and other processes running within the jail using
1205 flag appearing beside jailed processes.
1206 To see an active list of jails, use
1210 is enabled in the jail environment, you should be able to
1212 to the hostname or IP address of the jailed environment, and log
1213 in using the accounts you created previously.
1215 It is possible to have jails started at boot time.
1220 for more information.
1221 .Ss "Managing the Jail"
1222 Normal machine shutdown commands, such as
1227 cannot be used successfully within the jail.
1228 To kill all processes from within a jail, you may use one of the
1229 following commands, depending on what you want to accomplish:
1230 .Bd -literal -offset indent
1239 signals to all processes in the jail \(em be careful not to run this from
1240 the host environment!
1241 Once all of the jail's processes have died, unless the jail was created
1244 parameter, the jail will be removed.
1246 the intended use of the jail, you may also want to run
1247 .Pa /etc/rc.shutdown
1248 from within the jail.
1250 To shut down the jail from the outside, simply remove it with:
1251 .Bd -literal -offset indent
1255 which will run any commands specified by
1261 to any remaining jailed processes.
1264 .Pa /proc/ Ns Ar pid Ns Pa /status
1265 file contains, as its last field, the name of the jail in which the
1268 to indicate that the process is not running within a jail.
1271 command also shows a
1273 flag for processes in a jail.
1275 You can also list/kill processes based on their jail ID.
1276 To show processes and their jail ID, use the following command:
1278 .Dl "ps ax -o pid,jid,args"
1280 To show and then kill processes in jail number 3 use the following commands:
1281 .Bd -literal -offset indent
1288 .Ss "Jails and File Systems"
1289 It is not possible to
1293 any file system inside a jail unless the file system is marked
1294 jail-friendly, the jail's
1296 parameter is set, and the jail's
1298 parameter is lower than 2.
1300 Multiple jails sharing the same file system can influence each other.
1301 For example, a user in one jail can fill the file system,
1302 leaving no space for processes in the other jail.
1305 to prevent this will not work either, as the file system quotas
1306 are not aware of jails but only look at the user and group IDs.
1307 This means the same user ID in two jails share a single file
1309 One would need to use one file system per jail to make this work.
1310 .Ss "Sysctl MIB Entries"
1312 .Va security.jail.jailed
1313 can be used to determine if a process is running inside a jail (value
1314 is one) or not (value is zero).
1317 .Va security.jail.jail_max_af_ips
1318 determines how may address per address family a jail may have.
1321 Some MIB variables have per-jail settings.
1322 Changes to these variables by a jailed process do not affect the host
1323 environment, only the jail environment.
1325 .Va kern.securelevel ,
1326 .Va security.bsd.suser_enabled ,
1328 .Va kern.domainname ,
1332 .Ss "Hierarchical Jails"
1335 parameter, processes within a jail may be able to create jails of their own.
1336 These child jails are kept in a hierarchy, with jails only able to see and/or
1337 modify the jails they created (or those jails' children).
1338 Each jail has a read-only
1340 parameter, containing the
1342 of the jail that created it; a
1344 of 0 indicates the jail is a child of the current jail (or is a top-level
1345 jail if the current process isn't jailed).
1347 Jailed processes are not allowed to confer greater permissions than they
1348 themselves are given, e.g., if a jail is created with
1350 it is not able to create a jail with
1353 Similarly, such restrictions as
1357 may not be bypassed in child jails.
1359 A child jail may in turn create its own child jails if its own
1361 parameter is set (remember it is zero by default).
1362 These jails are visible to and can be modified by their parent and all
1365 Jail names reflect this hierarchy, with a full name being an MIB-type string
1367 For example, if a base system process creates a jail
1369 and a process under that jail creates another jail
1371 then the second jail will be seen as
1373 in the base system (though it is only seen as
1375 to any processes inside jail
1377 Jids on the other hand exist in a single space, and each jail must have a
1380 Like the names, a child jail's
1382 appears relative to its creator's own
1384 This is by virtue of the child jail being created in the chrooted
1385 environment of the first jail.
1428 Hierarchical/extensible jails were introduced in
1430 The configuration file was introduced in
1434 The jail feature was written by
1435 .An Poul-Henning Kamp
1437 who contributed it to
1441 wrote the extended documentation, found a few bugs, added
1442 a few new features, and cleaned up the userland jail environment.
1445 added multi-IP jail support for IPv4 and IPv6 based on a patch
1447 .An Pawel Jakub Dawidek
1451 added the extensible jail parameters, hierarchical jails,
1452 and the configuration file.
1454 It might be a good idea to add an
1455 address alias flag such that daemons listening on all IPs
1457 will not bind on that address, which would facilitate building a safe
1458 host environment such that host daemons do not impose on services offered
1460 Currently, the simplest answer is to minimize services
1461 offered on the host, possibly limiting it to services offered from
1463 which is easily configurable.
1465 Great care should be taken when managing directories visible within the jail.
1466 For example, if a jailed process has its current working directory set to a
1467 directory that is moved out of the jail's chroot, then the process may gain
1468 access to the file space outside of the jail.
1469 It is recommended that directories always be copied, rather than moved, out
1472 In addition, there are several ways in which an unprivileged user
1473 outside the jail can cooperate with a privileged user inside the jail
1474 and thereby obtain elevated privileges in the host environment.
1475 Most of these attacks can be mitigated by ensuring that the jail root
1476 is not accessible to unprivileged users in the host environment.
1477 Regardless, as a general rule, untrusted users with privileged access
1478 to a jail should not be given access to the host environment.