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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 [ Ns Ar ,... Ns ] Ar command ...
69 utility creates new jails, or modifies or removes existing jails.
70 It can also print a list of configured jails and their parameters.
73 is specified via parameters on the command line, or in the
77 At least one of the options
84 These options are used alone or in combination to describe the operation to
86 .Bl -tag -width indent
93 parameters (if specified on the command line)
94 must not refer to an existing jail.
96 Exhibit a list of all configured non-wildcard jails and their parameters.
97 No jail creation, modification or removal performed if this option is used.
100 string is used to separate parameters.
103 utility to list running jails.
105 Modify an existing jail.
110 parameters must exist and refer to an existing jail.
111 Some parameters may not be changed on a running jail.
115 specified by jid or name.
116 All jailed processes are killed, and all jails that are
117 children of this jail are also
120 Restart an existing jail.
121 The jail is first removed and then re-created, as if
125 were run in succession.
127 Create a jail if it does not exist, or modify the jail if it does exist.
129 Modify an existing jail.
130 The jail may be restarted if necessary to modify parameters than could
131 not otherwise be changed.
133 Create a jail if it doesn't exist, or modify (and possibly restart) the
134 jail if it does exist.
137 Other available options are:
138 .Bl -tag -width indent
140 Allow making changes to a dying jail, equivalent to the
143 .It Fl f Ar conf_file
144 Use configuration file
146 instead of the default
153 and add all IP addresses returned by the resolver
154 to the list of addresses for this jail.
155 This is equivalent to the
159 Output (only) the jail identifier of the newly created jail(s).
166 file, containing the parameters used to start the jail.
168 Run commands in a clean environment.
169 This is deprecated and is equivalent to the exec.clean parameter.
172 This is deprecated and is equivalent to the
176 Limit the number of commands from
178 that can run simultaneously.
180 Suppress the message printed whenever a jail is created, modified or removed.
181 Only error messages will be printed.
185 option that removes an existing jail without using the configuration file.
186 No removal-related parameters for this jail will be used \(em the jail will
188 .It Fl s Ar securelevel
191 MIB entry to the specified value inside the newly created jail.
192 This is deprecated and is equivalent to the
196 The user name from host environment as whom jailed commands should run.
197 This is deprecated and is equivalent to the
200 .Va exec.system_jail_user
203 The user name from the jailed environment as whom jailed commands should run.
204 This is deprecated and is equivalent to the
208 Print a message on every operation, such as running commands and
209 mounting filesystems.
212 If no arguments are given after the options, the operation (except
213 remove) will be performed on all jails specified in the
216 A single argument of a jail name will operate only on the specified jail.
221 options can also remove running jails that aren't in the
223 file, specified by name or jid.
227 is a wildcard that will operate on all jails, regardless of whether
230 this is the surest way for
233 If hierarchical jails exist, a partial-matching wildcard definition may
235 For example, an argument of
237 would apply to jails with names like
242 A jail may be specified with parameters directly on the command line.
245 file will not be used.
246 For backward compatibility, the command line may also have four fixed
247 parameters, without names:
253 This mode will always create a new jail, and the
257 options do not apply (and must not be present).
261 file, or on the command line, are generally of the form
263 Some parameters are boolean, and do not have a value but are set by the
264 name alone with or without a
270 They can also be given the values
274 Other parameters may have more than one value, specified as a
275 comma-separated list or with
277 in the configuration file (see
283 utility recognizes two classes of parameters.
284 There are the true jail
285 parameters that are passed to the kernel when the jail is created,
286 which can be seen with
288 and can (usually) be changed with
290 Then there are pseudo-parameters that are only used by
294 Jails have a set of core parameters, and kernel modules can add their own
296 The current set of available parameters can be retrieved via
297 .Dq Nm sysctl Fl d Va security.jail.param .
298 Any parameters not set will be given default values, often based on the
300 The core parameters are:
301 .Bl -tag -width indent
304 This will be assigned automatically to a new jail (or can be explicitly
305 set), and can be used to identify the jail for later modification, or
312 This is an arbitrary string that identifies a jail (except it may not
317 it can be passed to later
325 is supplied, a default is assumed that is the same as the
329 parameter is implied by the
331 file format, and need not be explicitly set when using the configuration
334 The directory which is to be the root of the jail.
335 Any commands run inside the jail, either by
339 are run from this directory.
341 A list of IPv4 addresses assigned to the jail.
342 If this is set, the jail is restricted to using only these addresses.
343 Any attempts to use other addresses fail, and attempts to use wildcard
344 addresses silently use the jailed address instead.
345 For IPv4 the first address given will be used as the source address
346 when source address selection on unbound sockets cannot find a better
348 It is only possible to start multiple jails with the same IP address
349 if none of the jails has more than this single overlapping IP address
352 A boolean option to change the formerly mentioned behaviour and disable
353 IPv4 source address selection for the jail in favour of the primary
354 IPv4 address of the jail.
355 Source address selection is enabled by default for all jails and the
357 setting of a parent jail is not inherited for any child jails.
359 Control the availability of IPv4 addresses.
362 to allow unrestricted access to all system addresses,
364 to restrict addresses via
368 to stop the jail from using IPv4 entirely.
371 parameter implies a value of
373 .It Va ip6.addr , Va ip6.saddrsel , Va ip6
374 A set of IPv6 options for the jail, the counterparts to
381 Create the jail with its own virtual network stack,
382 with its own network interfaces, addresses, routing table, etc.
383 The kernel must have been compiled with the
385 for this to be available.
388 to use the system network stack, possibly with restricted IP addresses,
391 to create a new network stack.
393 The hostname of the jail.
394 Other similar parameters are
395 .Va host.domainname ,
400 Set the origin of hostname and related information.
403 to use the system information and
405 for the jail to use the information from the above fields.
406 Setting any of the above fields implies a value of
409 The value of the jail's
412 A jail never has a lower securelevel than its parent system, but by
413 setting this parameter it may have a higher one.
414 If the system securelevel is changed, any jail securelevels will be at
417 The number of the devfs ruleset that is enforced for mounting devfs in
419 A value of zero (default) means no ruleset is enforced.
420 Descendant jails inherit the parent jail's devfs ruleset enforcement.
421 Mounting devfs inside a jail is possible only if the
424 .Va allow.mount.devfs
425 permissions are effective and
427 is set to a value lower than 2.
428 Devfs rules and rulesets cannot be viewed or modified from inside a jail.
430 NOTE: It is important that only appropriate device nodes in devfs be
431 exposed to a jail; access to disk devices in the jail may permit processes
432 in the jail to bypass the jail sandboxing by modifying files outside of
436 for information on how to use devfs rules to limit access to entries
437 in the per-jail devfs.
438 A simple devfs ruleset for jails is available as ruleset #4 in
439 .Pa /etc/defaults/devfs.rules .
441 The number of child jails allowed to be created by this jail (or by
442 other jails under this jail).
443 This limit is zero by default, indicating the jail is not allowed to
446 .Sx "Hierarchical Jails"
447 section for more information.
449 The number of descendants of this jail, including its own child jails
450 and any jails created under them.
451 .It Va enforce_statfs
452 This determines what information processes in a jail are able to get
454 It affects the behaviour of the following syscalls:
460 (as well as similar compatibility syscalls).
461 When set to 0, all mount points are available without any restrictions.
462 When set to 1, only mount points below the jail's chroot directory are
464 In addition to that, the path to the jail's chroot directory is removed
465 from the front of their pathnames.
466 When set to 2 (default), above syscalls can operate only on a mount-point
467 where the jail's chroot directory is located.
469 Setting this boolean parameter allows a jail to exist without any
471 Normally, a command is run as part of jail creation, and then the jail
472 is destroyed as its last process exits.
473 A new jail must have either the
479 pseudo-parameter set.
481 The ID of the cpuset associated with this jail (read-only).
483 This is true if the jail is in the process of shutting down (read-only).
487 of the parent of this jail, or zero if this is a top-level jail
490 The string for the jail's
494 The number for the jail's
498 Some restrictions of the jail environment may be set on a per-jail
500 With the exception of
501 .Va allow.set_hostname
503 .Va allow.reserved_ports ,
504 these boolean parameters are off by default.
505 .Bl -tag -width indent
506 .It Va allow.set_hostname
507 The jail's hostname may be changed via
512 A process within the jail has access to System V IPC primitives.
513 This is deprecated in favor of the per-module parameters (see below).
514 When this parameter is set, it is equivalent to setting
521 .It Va allow.raw_sockets
522 The jail root is allowed to create raw sockets.
523 Setting this parameter allows utilities like
527 to operate inside the jail.
528 If this is set, the source IP addresses are enforced to comply
529 with the IP address bound to the jail, regardless of whether or not
532 flag has been set on the socket.
533 Since raw sockets can be used to configure and interact with various
534 network subsystems, extra caution should be used where privileged access
535 to jails is given out to untrusted parties.
537 Normally, privileged users inside a jail are treated as unprivileged by
539 When this parameter is set, such users are treated as privileged, and
540 may manipulate system file flags subject to the usual constraints on
541 .Va kern.securelevel .
543 privileged users inside the jail will be able to mount and unmount file
544 system types marked as jail-friendly.
547 command can be used to find file system types available for mount from
549 This permission is effective only if
551 is set to a value lower than 2.
552 .It Va allow.mount.devfs
553 privileged users inside the jail will be able to mount and unmount the
555 This permission is effective only together with
559 is set to a value lower than 2.
560 The devfs ruleset should be restricted from the default by using the
564 The jail root may administer quotas on the jail's filesystem(s).
565 This includes filesystems that the jail may share with other jails or
566 with non-jailed parts of the system.
567 .It Va allow.read_msgbuf
568 Jailed users may read the kernel message buffer.
570 .Va security.bsd.unprivileged_read_msgbuf
571 MIB entry is zero, this will be restricted to the root user.
572 .It Va allow.socket_af
573 Sockets within a jail are normally restricted to IPv4, IPv6, local
574 (UNIX), and route. This allows access to other protocol stacks that
575 have not had jail functionality added to them.
577 Locking or unlocking physical pages in memory are normally not available
579 When this parameter is set, users may
584 .Va security.bsd.unprivileged_mlock
586 .It Va allow.reserved_ports
587 The jail root may bind to ports lower than 1024.
591 Kernel modules may add their own parameters, which only exist when the
593 These are typically headed under a parameter named after the module,
596 to give the jail full use of the module,
598 to encapsulate the jail in some module-specific way,
601 to make the module unavailable to the jail.
602 There also may be other parameters to define jail behavior within the module.
603 Module-specific parameters include:
604 .Bl -tag -width indent
605 .It Va allow.mount.fdescfs
606 privileged users inside the jail will be able to mount and unmount the
608 This permission is effective only together with
612 is set to a value lower than 2.
613 .It Va allow.mount.fusefs
614 privileged users inside the jail will be able to mount and unmount
615 fuse-based file systems.
616 This permission is effective only together with
620 is set to a value lower than 2.
621 .It Va allow.mount.nullfs
622 privileged users inside the jail will be able to mount and unmount the
624 This permission is effective only together with
628 is set to a value lower than 2.
629 .It Va allow.mount.procfs
630 privileged users inside the jail will be able to mount and unmount the
632 This permission is effective only together with
636 is set to a value lower than 2.
637 .It Va allow.mount.linprocfs
638 privileged users inside the jail will be able to mount and unmount the
639 linprocfs file system.
640 This permission is effective only together with
644 is set to a value lower than 2.
645 .It Va allow.mount.linsysfs
646 privileged users inside the jail will be able to mount and unmount the
647 linsysfs file system.
648 This permission is effective only together with
652 is set to a value lower than 2.
653 .It Va allow.mount.tmpfs
654 privileged users inside the jail will be able to mount and unmount the
656 This permission is effective only together with
660 is set to a value lower than 2.
661 .It Va allow.mount.zfs
662 privileged users inside the jail will be able to mount and unmount the
664 This permission is effective only together with
668 is set to a value lower than 2.
671 for information on how to configure the ZFS filesystem to operate from
676 This flag is only available when the
678 kernel module is loaded.
680 Determine how a jail's Linux emulation environment appears.
683 will keep the same environment, and
685 will give the jail its own environment (still originally inherited when
686 the jail is created).
687 .It Va linux.osname , linux.osrelease , linux.oss_version
688 The Linux OS name, OS release, and OSS version associated with this jail.
690 Allow access to SYSV IPC message primitives.
693 all IPC objects on the system are visible to this jail, whether they
694 were created by the jail itself, the base system, or other jails.
697 the jail will have its own key namespace, and can only see the objects
699 the system (or parent jail) has access to the jail's objects, but not to
703 the jail cannot perform any sysvmsg-related system calls.
704 .It Va sysvsem, sysvshm
705 Allow access to SYSV IPC semaphore and shared memory primitives, in the
710 There are pseudo-parameters that are not passed to the kernel, but are
713 to set up the jail environment, often by running specified commands
714 when jails are created or removed.
717 command parameters are
719 command lines that are run in either the system or jail environment.
720 They may be given multiple values, which would run the specified
721 commands in sequence.
722 All commands must succeed (return a zero exit status), or the jail will
723 not be created or removed, as appropriate.
725 The pseudo-parameters are:
726 .Bl -tag -width indent
728 Command(s) to run in the system environment to prepare a jail for creation.
729 These commands are executed before assigning IP addresses and mounting
730 filesystems, so they may be used to create a new jail filesystem if it does
733 Command(s) to run in the system environment before a jail is created.
735 Command(s) to run in the system environment right after a jail has been
736 created, but before commands (or services) get executed in the jail.
738 Command(s) to run in the jail environment when a jail is created.
739 A typical command to run is
744 for use when specifying a jail directly on the command line.
745 Unlike other parameters whose value is a single string,
747 uses the remainder of the
749 command line as its own arguments.
750 .It Va exec.poststart
751 Command(s) to run in the system environment after a jail is created,
754 commands have completed.
756 Command(s) to run in the system environment before a jail is removed.
758 Command(s) to run in the jail environment before a jail is removed,
761 commands have completed.
762 A typical command to run is
763 .Dq sh /etc/rc.shutdown jail .
765 Command(s) to run in the system environment after a jail is removed.
767 Command(s) to run in the system environment after all other actions are done.
768 These commands are executed after unmounting filesystems and removing IP
769 addresses, so they may be used to remove a jail filesystem if it is no longer
772 Run commands in a clean environment.
773 The environment is discarded except for
774 .Ev HOME , SHELL , TERM
780 are set to the target login's default values.
782 is set to the target login.
784 is imported from the current environment.
785 The environment variables from the login class capability database for the
786 target login are also set.
787 .It Va exec.jail_user
788 The user to run commands as, when running in the jail environment.
789 The default is to run the commands as the current user.
790 .It Va exec.system_jail_user
791 This boolean option looks for the
795 file, instead of in the jail's file.
796 .It Va exec.system_user
797 The user to run commands as, when running in the system environment.
798 The default is to run the commands as the current user.
800 The maximum amount of time to wait for a command to complete, in
802 If a command is still running after this timeout has passed,
803 the jail will not be created or removed, as appropriate.
804 .It Va exec.consolelog
805 A file to direct command output (stdout and stderr) to.
807 The FIB (routing table) to set when running commands inside the jail.
809 The maximum amount of time to wait for a jail's processes to exit
812 signal (which happens after the
814 commands have completed).
815 After this many seconds have passed, the jail will be removed, which
816 will kill any remaining processes.
817 If this is set to zero, no
819 is sent and the jail is immediately removed.
820 The default is 10 seconds.
822 A network interface to add the jail's IP addresses
827 An alias for each address will be added to the interface before the
828 jail is created, and will be removed from the interface after the
831 In addition to the IP addresses that are passed to the kernel, an
832 interface, netmask and additional parameters (as supported by
834 may also be specified, in the form
835 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
836 If an interface is given before the IP address, an alias for the address
837 will be added to that interface, as it is with the
840 If a netmask in either dotted-quad or CIDR form is given
841 after an IP address, it will be used when adding the IP alias.
842 If additional parameters are specified then they will also be used when
845 In addition to the IP addresses that are passed to the kernel,
846 an interface, prefix and additional parameters (as supported by
848 may also be specified, in the form
849 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
850 .It Va vnet.interface
851 A network interface to give to a vnet-enabled jail after is it created.
852 The interface will automatically be released when the jail is removed.
856 parameter and add all IP addresses returned by the resolver
857 to the list of addresses
862 This may affect default address selection for outgoing IPv4 connections
864 The address first returned by the resolver for each address family
865 will be used as the primary address.
867 A filesystem to mount before creating the jail (and to unmount after
868 removing it), given as a single
874 format file containing filesystems to mount before creating a jail.
878 filesystem on the chrooted
880 directory, and apply the ruleset in the
882 parameter (or a default of ruleset 4: devfsrules_jail)
883 to restrict the devices visible inside the jail.
887 filesystem on the chrooted
893 filesystem on the chrooted
897 Allow making changes to a
901 Specify a jail (or jails) that this jail depends on.
902 When this jail is to be created, any jail(s) it depends on must already exist.
903 If not, they will be created automatically, up to the completion of the last
905 command, before any action will taken to create this jail.
906 When jails are removed the opposite is true:
907 this jail will be removed, up to the last
909 command, before any jail(s) it depends on are stopped.
912 Jails are typically set up using one of two philosophies: either to
913 constrain a specific application (possibly running with privilege), or
915 .Dq "virtual system image"
916 running a variety of daemons and services.
917 In both cases, a fairly complete file system install of
920 required, so as to provide the necessary command line tools, daemons,
921 libraries, application configuration files, etc.
922 However, for a virtual server configuration, a fair amount of
923 additional work is required so as to replace the
926 This manual page documents the configuration steps necessary to support
927 either of these steps, although the configuration steps may need to be
928 refined based on local requirements.
929 .Ss "Setting up a Jail Directory Tree"
930 To set up a jail directory tree containing an entire
932 distribution, the following
934 command script can be used:
939 make world DESTDIR=$D
940 make distribution DESTDIR=$D
943 In many cases this example would put far more in the jail than needed.
944 In the other extreme case a jail might contain only one file:
945 the executable to be run in the jail.
947 We recommend experimentation, and caution that it is a lot easier to
950 jail and remove things until it stops working,
951 than it is to start with a
953 jail and add things until it works.
954 .Ss "Setting Up a Jail"
955 Do what was described in
956 .Sx "Setting Up a Jail Directory Tree"
957 to build the jail directory tree.
958 For the sake of this example, we will
959 assume you built it in
960 .Pa /data/jail/testjail ,
963 Substitute below as needed with your
964 own directory, IP address, and hostname.
965 .Ss "Setting up the Host Environment"
966 First, set up the real system's environment to be
968 For consistency, we will refer to the parent box as the
969 .Dq "host environment" ,
970 and to the jailed virtual machine as the
971 .Dq "jail environment" .
972 Since jails are implemented using IP aliases, one of the first things to do
973 is to disable IP services on the host system that listen on all local
974 IP addresses for a service.
975 If a network service is present in the host environment that binds all
976 available IP addresses rather than specific IP addresses, it may service
977 requests sent to jail IP addresses if the jail did not bind the port.
980 to only listen on the
981 appropriate IP address, and so forth.
984 in the host environment:
985 .Bd -literal -offset indent
987 inetd_flags="-wW -a 192.0.2.23"
992 is the native IP address for the host system, in this example.
993 Daemons that run out of
995 can be easily configured to use only the specified host IP address.
997 will need to be manually configured \(em for some this is possible through
999 flags entries; for others it is necessary to modify per-application
1000 configuration files, or to recompile the application.
1001 The following frequently deployed services must have their individual
1002 configuration files modified to limit the application to listening
1003 to a specific IP address:
1007 it is necessary to modify
1008 .Pa /etc/ssh/sshd_config .
1012 it is necessary to modify
1013 .Pa /etc/mail/sendmail.cf .
1017 it is necessary to modify
1018 .Pa /etc/namedb/named.conf .
1020 In addition, a number of services must be recompiled in order to run
1021 them in the host environment.
1022 This includes most applications providing services using
1029 In general, applications for which it is not possible to specify which
1030 IP address to bind should not be run in the host environment unless they
1031 should also service requests sent to jail IP addresses.
1033 NFS from the host environment may also cause confusion, and cannot be
1034 easily reconfigured to use only specific IPs, as some NFS services are
1035 hosted directly from the kernel.
1036 Any third-party network software running
1037 in the host environment should also be checked and configured so that it
1038 does not bind all IP addresses, which would result in those services also
1039 appearing to be offered by the jail environments.
1042 these daemons have been disabled or fixed in the host environment, it is
1043 best to reboot so that all daemons are in a known state, to reduce the
1044 potential for confusion later (such as finding that when you send mail
1045 to a jail, and its sendmail is down, the mail is delivered to the host,
1047 .Ss "Configuring the Jail"
1048 Start any jail for the first time without configuring the network
1049 interface so that you can clean it up a little and set up accounts.
1051 with any machine (virtual or not), you will need to set a root password, time
1053 Some of these steps apply only if you intend to run a full virtual server
1054 inside the jail; others apply both for constraining a particular application
1055 or for running a virtual server.
1057 Start a shell in the jail:
1058 .Bd -literal -offset indent
1059 jail -c path=/data/jail/testjail mount.devfs \\
1060 host.hostname=testhostname ip4.addr=192.0.2.100 \\
1064 Assuming no errors, you will end up with a shell prompt within the jail.
1067 and do the post-install configuration to set various configuration options,
1068 or perform these actions manually by editing
1072 .Bl -bullet -offset indent -compact
1075 .Pa /etc/resolv.conf
1076 so that name resolution within the jail will work correctly.
1084 Set a root password, probably different from the real host system.
1088 Add accounts for users in the jail environment.
1090 Install any packages the environment requires.
1093 You may also want to perform any package-specific configuration (web servers,
1094 SSH servers, etc), patch up
1095 .Pa /etc/syslog.conf
1096 so it logs as you would like, etc.
1097 If you are not using a virtual server, you may wish to modify
1099 in the host environment to listen on the syslog socket in the jail
1100 environment; in this example, the syslog socket would be stored in
1101 .Pa /data/jail/testjail/var/run/log .
1103 Exit from the shell, and the jail will be shut down.
1104 .Ss "Starting the Jail"
1105 You are now ready to restart the jail and bring up the environment with
1106 all of its daemons and other programs.
1107 Create an entry for the jail in
1108 .Pa /etc/jail.conf :
1109 .Bd -literal -offset indent
1111 path = /tmp/jail/testjail;
1113 host.hostname = testhostname;
1114 ip4.addr = 192.0.2.100;
1116 exec.start = "/bin/sh /etc/rc";
1117 exec.stop = "/bin/sh /etc/rc.shutdown jail";
1121 To start a virtual server environment,
1123 is run to launch various daemons and services, and
1124 .Pa /etc/rc.shutdown
1125 is run to shut them down when the jail is removed.
1126 If you are running a single application in the jail,
1127 substitute the command used to start the application for
1128 .Dq /bin/sh /etc/rc ;
1129 there may be some script available to cleanly shut down the application,
1130 or it may be sufficient to go without a stop command, and have
1136 Start the jail by running:
1137 .Bd -literal -offset indent
1141 A few warnings may be produced; however, it should all work properly.
1142 You should be able to see
1145 and other processes running within the jail using
1149 flag appearing beside jailed processes.
1150 To see an active list of jails, use
1154 is enabled in the jail environment, you should be able to
1156 to the hostname or IP address of the jailed environment, and log
1157 in using the accounts you created previously.
1159 It is possible to have jails started at boot time.
1164 for more information.
1165 .Ss "Managing the Jail"
1166 Normal machine shutdown commands, such as
1171 cannot be used successfully within the jail.
1172 To kill all processes from within a jail, you may use one of the
1173 following commands, depending on what you want to accomplish:
1174 .Bd -literal -offset indent
1183 signals to all processes in the jail \(em be careful not to run this from
1184 the host environment!
1185 Once all of the jail's processes have died, unless the jail was created
1188 parameter, the jail will be removed.
1190 the intended use of the jail, you may also want to run
1191 .Pa /etc/rc.shutdown
1192 from within the jail.
1194 To shut down the jail from the outside, simply remove it with
1197 which will run any commands specified by
1203 to any remaining jailed processes.
1206 .Pa /proc/ Ns Ar pid Ns Pa /status
1207 file contains, as its last field, the name of the jail in which the
1210 to indicate that the process is not running within a jail.
1213 command also shows a
1215 flag for processes in a jail.
1217 You can also list/kill processes based on their jail ID.
1218 To show processes and their jail ID, use the following command:
1220 .Dl "ps ax -o pid,jid,args"
1222 To show and then kill processes in jail number 3 use the following commands:
1223 .Bd -literal -offset indent
1230 .Ss "Jails and File Systems"
1231 It is not possible to
1235 any file system inside a jail unless the file system is marked
1236 jail-friendly, the jail's
1238 parameter is set, and the jail's
1240 parameter is lower than 2.
1242 Multiple jails sharing the same file system can influence each other.
1243 For example, a user in one jail can fill the file system,
1244 leaving no space for processes in the other jail.
1247 to prevent this will not work either, as the file system quotas
1248 are not aware of jails but only look at the user and group IDs.
1249 This means the same user ID in two jails share a single file
1251 One would need to use one file system per jail to make this work.
1252 .Ss "Sysctl MIB Entries"
1254 .Va security.jail.jailed
1255 can be used to determine if a process is running inside a jail (value
1256 is one) or not (value is zero).
1259 .Va security.jail.max_af_ips
1260 determines how may address per address family a jail may have.
1263 Some MIB variables have per-jail settings.
1264 Changes to these variables by a jailed process do not affect the host
1265 environment, only the jail environment.
1267 .Va kern.securelevel ,
1269 .Va kern.domainname ,
1273 .Ss "Hierarchical Jails"
1276 parameter, processes within a jail may be able to create jails of their own.
1277 These child jails are kept in a hierarchy, with jails only able to see and/or
1278 modify the jails they created (or those jails' children).
1279 Each jail has a read-only
1281 parameter, containing the
1283 of the jail that created it; a
1285 of 0 indicates the jail is a child of the current jail (or is a top-level
1286 jail if the current process isn't jailed).
1288 Jailed processes are not allowed to confer greater permissions than they
1289 themselves are given, e.g., if a jail is created with
1291 it is not able to create a jail with
1294 Similarly, such restrictions as
1298 may not be bypassed in child jails.
1300 A child jail may in turn create its own child jails if its own
1302 parameter is set (remember it is zero by default).
1303 These jails are visible to and can be modified by their parent and all
1306 Jail names reflect this hierarchy, with a full name being an MIB-type string
1308 For example, if a base system process creates a jail
1310 and a process under that jail creates another jail
1312 then the second jail will be seen as
1314 in the base system (though it is only seen as
1316 to any processes inside jail
1318 Jids on the other hand exist in a single space, and each jail must have a
1321 Like the names, a child jail's
1323 appears relative to its creator's own
1325 This is by virtue of the child jail being created in the chrooted
1326 environment of the first jail.
1367 Hierarchical/extensible jails were introduced in
1369 The configuration file was introduced in
1373 The jail feature was written by
1374 .An Poul-Henning Kamp
1376 who contributed it to
1380 wrote the extended documentation, found a few bugs, added
1381 a few new features, and cleaned up the userland jail environment.
1384 added multi-IP jail support for IPv4 and IPv6 based on a patch
1386 .An Pawel Jakub Dawidek
1390 added the extensible jail parameters, hierarchical jails,
1391 and the configuration file.
1393 It might be a good idea to add an
1394 address alias flag such that daemons listening on all IPs
1396 will not bind on that address, which would facilitate building a safe
1397 host environment such that host daemons do not impose on services offered
1399 Currently, the simplest answer is to minimize services
1400 offered on the host, possibly limiting it to services offered from
1402 which is easily configurable.
1404 Great care should be taken when managing directories visible within the jail.
1405 For example, if a jailed process has its current working directory set to a
1406 directory that is moved out of the jail's chroot, then the process may gain
1407 access to the file space outside of the jail.
1408 It is recommended that directories always be copied, rather than moved, out
1411 In addition, there are several ways in which an unprivileged user
1412 outside the jail can cooperate with a privileged user inside the jail
1413 and thereby obtain elevated privileges in the host environment.
1414 Most of these attacks can be mitigated by ensuring that the jail root
1415 is not accessible to unprivileged users in the host environment.
1416 Regardless, as a general rule, untrusted users with privileged access
1417 to a jail should not be given access to the host environment.