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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 Clean up after an already-removed jail, running commands and operations
149 that are typically run following jail removal.
150 .It Fl f Ar conf_file
151 Use configuration file
153 instead of the default
160 and add all IP addresses returned by the resolver
161 to the list of addresses for this jail.
162 This is equivalent to the
166 Output (only) the jail identifier of the newly created jail(s).
173 file, containing the parameters used to start the jail.
175 Run commands in a clean environment.
176 This is deprecated and is equivalent to the exec.clean parameter.
179 This is deprecated and is equivalent to the
183 Limit the number of commands from
185 that can run simultaneously.
187 Suppress the message printed whenever a jail is created, modified or removed.
188 Only error messages will be printed.
192 option that removes an existing jail without using the configuration file.
193 No removal-related parameters for this jail will be used \(em the jail will
195 .It Fl s Ar securelevel
198 MIB entry to the specified value inside the newly created jail.
199 This is deprecated and is equivalent to the
203 The user name from host environment as whom jailed commands should run.
204 This is deprecated and is equivalent to the
207 .Va exec.system_jail_user
210 The user name from the jailed environment as whom jailed commands should run.
211 This is deprecated and is equivalent to the
215 Print a message on every operation, such as running commands and
216 mounting filesystems.
218 This is deprecated and is equivalent to the
220 parameter, which is also deprecated.
221 It used to allow making changes to a
224 Now such jails are always replaced when a new jail is created with the same
230 If no arguments are given after the options, the operation (except
231 remove) will be performed on all jails specified in the
234 A single argument of a jail name will operate only on the specified jail.
239 options can also remove running jails that aren't in the
241 file, specified by name or jid.
245 is a wildcard that will operate on all jails, regardless of whether
248 this is the surest way for
251 If hierarchical jails exist, a partial-matching wildcard definition may
253 For example, an argument of
255 would apply to jails with names like
260 A jail may also be specified via parameters directly on the command line in
262 form, ignoring the contents of
264 For backward compatibility, the command line may also have four fixed
265 parameters, without names:
274 file, or on the command line, are generally of the form
276 Some parameters are boolean, and do not have a value but are set by the
277 name alone with or without a
283 They can also be given the values
287 Other parameters may have more than one value, specified as a
288 comma-separated list or with
290 in the configuration file (see
296 utility recognizes two classes of parameters.
297 There are the true jail
298 parameters that are passed to the kernel when the jail is created,
299 which can be seen with
301 and can (usually) be changed with
303 Then there are pseudo-parameters that are only used by
307 Jails have a set of core parameters, and kernel modules can add their own
309 The current set of available parameters can be retrieved via
310 .Dq Nm sysctl Fl d Va security.jail.param .
311 Any parameters not set will be given default values, often based on the
313 The core parameters are:
314 .Bl -tag -width indent
317 This will be assigned automatically to a new jail (or can be explicitly
318 set), and can be used to identify the jail for later modification, or
325 This is an arbitrary string that identifies a jail (except it may not
330 it can be passed to later
338 is supplied, a default is assumed that is the same as the
342 parameter is implied by the
344 file format, and need not be explicitly set when using the configuration
347 The directory which is to be the root of the jail.
348 Any commands run inside the jail, either by
352 are run from this directory.
354 A list of IPv4 addresses assigned to the jail.
355 If this is set, the jail is restricted to using only these addresses.
356 Any attempts to use other addresses fail, and attempts to use wildcard
357 addresses silently use the jailed address instead.
358 For IPv4 the first address given will be used as the source address
359 when source address selection on unbound sockets cannot find a better
361 It is only possible to start multiple jails with the same IP address
362 if none of the jails has more than this single overlapping IP address
365 A boolean option to change the formerly mentioned behaviour and disable
366 IPv4 source address selection for the jail in favour of the primary
367 IPv4 address of the jail.
368 Source address selection is enabled by default for all jails and the
370 setting of a parent jail is not inherited for any child jails.
372 Control the availability of IPv4 addresses.
375 to allow unrestricted access to all system addresses,
377 to restrict addresses via
381 to stop the jail from using IPv4 entirely.
384 parameter implies a value of
386 .It Va ip6.addr , Va ip6.saddrsel , Va ip6
387 A set of IPv6 options for the jail, the counterparts to
394 Create the jail with its own virtual network stack,
395 with its own network interfaces, addresses, routing table, etc.
396 The kernel must have been compiled with the
398 for this to be available.
401 to use the system network stack, possibly with restricted IP addresses,
404 to create a new network stack.
406 The hostname of the jail.
407 Other similar parameters are
408 .Va host.domainname ,
413 Set the origin of hostname and related information.
416 to use the system information and
418 for the jail to use the information from the above fields.
419 Setting any of the above fields implies a value of
422 The value of the jail's
425 A jail never has a lower securelevel than its parent system, but by
426 setting this parameter it may have a higher one.
427 If the system securelevel is changed, any jail securelevels will be at
430 The number of the devfs ruleset that is enforced for mounting devfs in
432 A value of zero (default) means no ruleset is enforced.
433 Descendant jails inherit the parent jail's devfs ruleset enforcement.
434 Mounting devfs inside a jail is possible only if the
437 .Va allow.mount.devfs
438 permissions are effective and
440 is set to a value lower than 2.
441 Devfs rules and rulesets cannot be viewed or modified from inside a jail.
443 NOTE: It is important that only appropriate device nodes in devfs be
444 exposed to a jail; access to disk devices in the jail may permit processes
445 in the jail to bypass the jail sandboxing by modifying files outside of
449 for information on how to use devfs rules to limit access to entries
450 in the per-jail devfs.
451 A simple devfs ruleset for jails is available as ruleset #4 in
452 .Pa /etc/defaults/devfs.rules .
454 The number of child jails allowed to be created by this jail (or by
455 other jails under this jail).
456 This limit is zero by default, indicating the jail is not allowed to
459 .Sx "Hierarchical Jails"
460 section for more information.
462 The number of descendants of this jail, including its own child jails
463 and any jails created under them.
464 .It Va enforce_statfs
465 This determines what information processes in a jail are able to get
467 It affects the behaviour of the following syscalls:
473 (as well as similar compatibility syscalls).
474 When set to 0, all mount points are available without any restrictions.
475 When set to 1, only mount points below the jail's chroot directory are
477 In addition to that, the path to the jail's chroot directory is removed
478 from the front of their pathnames.
479 When set to 2 (default), above syscalls can operate only on a mount-point
480 where the jail's chroot directory is located.
482 Setting this boolean parameter allows a jail to exist without any
484 Normally, a command is run as part of jail creation, and then the jail
485 is destroyed as its last process exits.
486 A new jail must have either the
492 pseudo-parameter set.
494 The ID of the cpuset associated with this jail (read-only).
496 This is true if the jail is in the process of shutting down (read-only).
500 of the parent of this jail, or zero if this is a top-level jail
503 The string for the jail's
507 The number for the jail's
511 Some restrictions of the jail environment may be set on a per-jail
513 With the exception of
514 .Va allow.set_hostname
516 .Va allow.reserved_ports ,
517 these boolean parameters are off by default.
518 .Bl -tag -width indent
519 .It Va allow.set_hostname
520 The jail's hostname may be changed via
525 A process within the jail has access to System V IPC primitives.
526 This is deprecated in favor of the per-module parameters (see below).
527 When this parameter is set, it is equivalent to setting
534 .It Va allow.raw_sockets
535 The jail root is allowed to create raw sockets.
536 Setting this parameter allows utilities like
540 to operate inside the jail.
541 If this is set, the source IP addresses are enforced to comply
542 with the IP address bound to the jail, regardless of whether or not
545 flag has been set on the socket.
546 Since raw sockets can be used to configure and interact with various
547 network subsystems, extra caution should be used where privileged access
548 to jails is given out to untrusted parties.
550 Normally, privileged users inside a jail are treated as unprivileged by
552 When this parameter is set, such users are treated as privileged, and
553 may manipulate system file flags subject to the usual constraints on
554 .Va kern.securelevel .
556 privileged users inside the jail will be able to mount and unmount file
557 system types marked as jail-friendly.
560 command can be used to find file system types available for mount from
562 This permission is effective only if
564 is set to a value lower than 2.
565 .It Va allow.mount.devfs
566 privileged users inside the jail will be able to mount and unmount the
568 This permission is effective only together with
572 is set to a value lower than 2.
573 The devfs ruleset should be restricted from the default by using the
577 The jail root may administer quotas on the jail's filesystem(s).
578 This includes filesystems that the jail may share with other jails or
579 with non-jailed parts of the system.
580 .It Va allow.read_msgbuf
581 Jailed users may read the kernel message buffer.
583 .Va security.bsd.unprivileged_read_msgbuf
584 MIB entry is zero, this will be restricted to the root user.
585 .It Va allow.socket_af
586 Sockets within a jail are normally restricted to IPv4, IPv6, local
588 This allows access to other protocol stacks that have not had jail
589 functionality added to them.
591 Locking or unlocking physical pages in memory are normally not available
593 When this parameter is set, users may
598 .Va security.bsd.unprivileged_mlock
608 daemons are permitted to run inside a properly configured vnet-enabled jail.
609 The jail's root must be a file system mount point and
611 must not be set to 0, so that
613 can export file systems visible within the jail.
615 must be set to 1 if file systems mounted under the
616 jail's file system need to be exported by
618 For exporting only the jail's file system, a setting of 2
620 If the kernel configuration does not include the
624 must be loaded outside of the jails.
625 This is normally done by adding
631 file outside of the jails.
634 is to be run in a jail, either the kernel
636 option needs to be specified or
644 file outside of the jails.
645 .It Va allow.reserved_ports
646 The jail root may bind to ports lower than 1024.
647 .It Va allow.unprivileged_proc_debug
648 Unprivileged processes in the jail may use debugging facilities.
650 The value of the jail's
651 .Va security.bsd.suser_enabled
653 The super-user will be disabled automatically if its parent system has it
655 The super-user is enabled by default.
657 Allow privileged process in the jail to manipulate filesystem extended
658 attributes in the system namespace.
662 Kernel modules may add their own parameters, which only exist when the
664 These are typically headed under a parameter named after the module,
667 to give the jail full use of the module,
669 to encapsulate the jail in some module-specific way,
672 to make the module unavailable to the jail.
673 There also may be other parameters to define jail behavior within the module.
674 Module-specific parameters include:
675 .Bl -tag -width indent
676 .It Va allow.mount.fdescfs
677 privileged users inside the jail will be able to mount and unmount the
679 This permission is effective only together with
683 is set to a value lower than 2.
684 .It Va allow.mount.fusefs
685 privileged users inside the jail will be able to mount and unmount
686 fuse-based file systems.
687 This permission is effective only together with
691 is set to a value lower than 2.
692 .It Va allow.mount.nullfs
693 privileged users inside the jail will be able to mount and unmount the
695 This permission is effective only together with
699 is set to a value lower than 2.
700 .It Va allow.mount.procfs
701 privileged users inside the jail will be able to mount and unmount the
703 This permission is effective only together with
707 is set to a value lower than 2.
708 .It Va allow.mount.linprocfs
709 privileged users inside the jail will be able to mount and unmount the
710 linprocfs file system.
711 This permission is effective only together with
715 is set to a value lower than 2.
716 .It Va allow.mount.linsysfs
717 privileged users inside the jail will be able to mount and unmount the
718 linsysfs file system.
719 This permission is effective only together with
723 is set to a value lower than 2.
724 .It Va allow.mount.tmpfs
725 privileged users inside the jail will be able to mount and unmount the
727 This permission is effective only together with
731 is set to a value lower than 2.
732 .It Va allow.mount.zfs
733 privileged users inside the jail will be able to mount and unmount the
735 This permission is effective only together with
739 is set to a value lower than 2.
742 for information on how to configure the ZFS filesystem to operate from
747 This flag is only available when the
749 kernel module is loaded.
751 Determine how a jail's Linux emulation environment appears.
754 will keep the same environment, and
756 will give the jail its own environment (still originally inherited when
757 the jail is created).
758 .It Va linux.osname , linux.osrelease , linux.oss_version
759 The Linux OS name, OS release, and OSS version associated with this jail.
761 Allow access to SYSV IPC message primitives.
764 all IPC objects on the system are visible to this jail, whether they
765 were created by the jail itself, the base system, or other jails.
768 the jail will have its own key namespace, and can only see the objects
770 the system (or parent jail) has access to the jail's objects, but not to
774 the jail cannot perform any sysvmsg-related system calls.
775 .It Va sysvsem, sysvshm
776 Allow access to SYSV IPC semaphore and shared memory primitives, in the
781 There are pseudo-parameters that are not passed to the kernel, but are
784 to set up the jail environment, often by running specified commands
785 when jails are created or removed.
788 command parameters are
790 command lines that are run in either the system or jail environment.
791 They may be given multiple values, which would run the specified
792 commands in sequence.
793 All commands must succeed (return a zero exit status), or the jail will
794 not be created or removed, as appropriate.
796 The pseudo-parameters are:
797 .Bl -tag -width indent
799 Command(s) to run in the system environment to prepare a jail for creation.
800 These commands are executed before assigning IP addresses and mounting
801 filesystems, so they may be used to create a new jail filesystem if it does
804 Command(s) to run in the system environment before a jail is created.
806 Command(s) to run in the system environment right after a jail has been
807 created, but before commands (or services) get executed in the jail.
809 Command(s) to run in the jail environment when a jail is created.
810 A typical command to run is
815 for use when specifying a jail directly on the command line.
816 Unlike other parameters whose value is a single string,
818 uses the remainder of the
820 command line as its own arguments.
821 .It Va exec.poststart
822 Command(s) to run in the system environment after a jail is created,
825 commands have completed.
827 Command(s) to run in the system environment before a jail is removed.
829 Command(s) to run in the jail environment before a jail is removed,
832 commands have completed.
833 A typical command to run is
834 .Dq sh /etc/rc.shutdown jail .
836 Command(s) to run in the system environment after a jail is removed.
838 Command(s) to run in the system environment after all other actions are done.
839 These commands are executed after unmounting filesystems and removing IP
840 addresses, so they may be used to remove a jail filesystem if it is no longer
843 Run commands in a clean environment.
844 The environment is discarded except for
845 .Ev HOME , SHELL , TERM
851 are set to the target login's default values.
853 is set to the target login.
855 is imported from the current environment.
856 The environment variables from the login class capability database for the
857 target login are also set.
858 .It Va exec.jail_user
859 The user to run commands as, when running in the jail environment.
860 The default is to run the commands as the current user.
861 .It Va exec.system_jail_user
862 This boolean option looks for the
866 file, instead of in the jail's file.
867 .It Va exec.system_user
868 The user to run commands as, when running in the system environment.
869 The default is to run the commands as the current user.
871 The maximum amount of time to wait for a command to complete, in
873 If a command is still running after this timeout has passed,
874 the jail will not be created or removed, as appropriate.
875 .It Va exec.consolelog
876 A file to direct command output (stdout and stderr) to.
878 The FIB (routing table) to set when running commands inside the jail.
880 The maximum amount of time to wait for a jail's processes to exit
883 signal (which happens after the
885 commands have completed).
886 After this many seconds have passed, the jail will be removed, which
887 will kill any remaining processes.
888 If this is set to zero, no
890 is sent and the jail is immediately removed.
891 The default is 10 seconds.
893 A network interface to add the jail's IP addresses
898 An alias for each address will be added to the interface before the
899 jail is created, and will be removed from the interface after the
902 In addition to the IP addresses that are passed to the kernel, an
903 interface, netmask and additional parameters (as supported by
905 may also be specified, in the form
906 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
907 If an interface is given before the IP address, an alias for the address
908 will be added to that interface, as it is with the
911 If a netmask in either dotted-quad or CIDR form is given
912 after an IP address, it will be used when adding the IP alias.
913 If additional parameters are specified then they will also be used when
916 In addition to the IP addresses that are passed to the kernel,
917 an interface, prefix and additional parameters (as supported by
919 may also be specified, in the form
920 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
921 .It Va vnet.interface
922 A network interface to give to a vnet-enabled jail after is it created.
923 The interface will automatically be released when the jail is removed.
925 A list of ZFS datasets to be attached to the jail.
931 for information on how to configure a ZFS dataset to be operated from
936 parameter and add all IP addresses returned by the resolver
937 to the list of addresses
942 This may affect default address selection for outgoing IPv4 connections
944 The address first returned by the resolver for each address family
945 will be used as the primary address.
947 A filesystem to mount before creating the jail (and to unmount after
948 removing it), given as a single
954 format file containing filesystems to mount before creating a jail.
958 filesystem on the chrooted
960 directory, and apply the ruleset in the
962 parameter (or a default of ruleset 4: devfsrules_jail)
963 to restrict the devices visible inside the jail.
967 filesystem on the chrooted
973 filesystem on the chrooted
977 This is deprecated and has no effect.
978 It used to allow making changes to a
981 Now such jails are always replaced when a new jail is created with the same
986 Specify a jail (or jails) that this jail depends on.
987 When this jail is to be created, any jail(s) it depends on must already exist.
988 If not, they will be created automatically, up to the completion of the last
990 command, before any action will taken to create this jail.
991 When jails are removed the opposite is true:
992 this jail will be removed, up to the last
994 command, before any jail(s) it depends on are stopped.
997 Jails are typically set up using one of two philosophies: either to
998 constrain a specific application (possibly running with privilege), or
1000 .Dq "virtual system image"
1001 running a variety of daemons and services.
1002 In both cases, a fairly complete file system install of
1005 required, so as to provide the necessary command line tools, daemons,
1006 libraries, application configuration files, etc.
1007 However, for a virtual server configuration, a fair amount of
1008 additional work is required so as to replace the
1011 This manual page documents the configuration steps necessary to support
1012 either of these steps, although the configuration steps may need to be
1013 refined based on local requirements.
1014 .Ss "Setting up a Jail Directory Tree"
1015 To set up a jail directory tree containing an entire
1017 distribution, the following
1019 command script can be used:
1020 .Bd -literal -offset indent
1024 make world DESTDIR=$D
1025 make distribution DESTDIR=$D
1028 In many cases this example would put far more in the jail than needed.
1029 In the other extreme case a jail might contain only one file:
1030 the executable to be run in the jail.
1032 We recommend experimentation, and caution that it is a lot easier to
1035 jail and remove things until it stops working,
1036 than it is to start with a
1038 jail and add things until it works.
1039 .Ss "Setting Up a Jail"
1040 Do what was described in
1041 .Sx "Setting Up a Jail Directory Tree"
1042 to build the jail directory tree.
1043 For the sake of this example, we will
1044 assume you built it in
1045 .Pa /data/jail/testjail ,
1048 Substitute below as needed with your
1049 own directory, IP address, and hostname.
1050 .Ss "Setting up the Host Environment"
1051 First, set up the real system's environment to be
1053 For consistency, we will refer to the parent box as the
1054 .Dq "host environment" ,
1055 and to the jailed virtual machine as the
1056 .Dq "jail environment" .
1057 Since jails are implemented using IP aliases, one of the first things to do
1058 is to disable IP services on the host system that listen on all local
1059 IP addresses for a service.
1060 If a network service is present in the host environment that binds all
1061 available IP addresses rather than specific IP addresses, it may service
1062 requests sent to jail IP addresses if the jail did not bind the port.
1065 to only listen on the
1066 appropriate IP address, and so forth.
1067 Add the following to
1069 in the host environment:
1070 .Bd -literal -offset indent
1071 sendmail_enable="NO"
1072 inetd_flags="-wW -a 192.0.2.23"
1077 is the native IP address for the host system, in this example.
1078 Daemons that run out of
1080 can be easily configured to use only the specified host IP address.
1082 will need to be manually configured \(em for some this is possible through
1084 flags entries; for others it is necessary to modify per-application
1085 configuration files, or to recompile the application.
1086 The following frequently deployed services must have their individual
1087 configuration files modified to limit the application to listening
1088 to a specific IP address:
1092 it is necessary to modify
1093 .Pa /etc/ssh/sshd_config .
1097 it is necessary to modify
1098 .Pa /etc/mail/sendmail.cf .
1100 In addition, a number of services must be recompiled in order to run
1101 them in the host environment.
1102 This includes most applications providing services using
1109 In general, applications for which it is not possible to specify which
1110 IP address to bind should not be run in the host environment unless they
1111 should also service requests sent to jail IP addresses.
1113 NFS from the host environment may also cause confusion, and cannot be
1114 easily reconfigured to use only specific IPs, as some NFS services are
1115 hosted directly from the kernel.
1116 Any third-party network software running
1117 in the host environment should also be checked and configured so that it
1118 does not bind all IP addresses, which would result in those services also
1119 appearing to be offered by the jail environments.
1122 these daemons have been disabled or fixed in the host environment, it is
1123 best to reboot so that all daemons are in a known state, to reduce the
1124 potential for confusion later (such as finding that when you send mail
1125 to a jail, and its sendmail is down, the mail is delivered to the host,
1127 .Ss "Configuring the Jail"
1128 Start any jail for the first time without configuring the network
1129 interface so that you can clean it up a little and set up accounts.
1131 with any machine (virtual or not), you will need to set a root password, time
1133 Some of these steps apply only if you intend to run a full virtual server
1134 inside the jail; others apply both for constraining a particular application
1135 or for running a virtual server.
1137 Start a shell in the jail:
1138 .Bd -literal -offset indent
1139 jail -c path=/data/jail/testjail mount.devfs \\
1140 host.hostname=testhostname ip4.addr=192.0.2.100 \\
1144 Assuming no errors, you will end up with a shell prompt within the jail.
1147 and do the post-install configuration to set various configuration options,
1148 or perform these actions manually by editing
1152 .Bl -bullet -offset indent -compact
1155 .Pa /etc/resolv.conf
1156 so that name resolution within the jail will work correctly.
1164 Set a root password, probably different from the real host system.
1168 Add accounts for users in the jail environment.
1170 Install any packages the environment requires.
1173 You may also want to perform any package-specific configuration (web servers,
1174 SSH servers, etc), patch up
1175 .Pa /etc/syslog.conf
1176 so it logs as you would like, etc.
1177 If you are not using a virtual server, you may wish to modify
1179 in the host environment to listen on the syslog socket in the jail
1180 environment; in this example, the syslog socket would be stored in
1181 .Pa /data/jail/testjail/var/run/log .
1183 Exit from the shell, and the jail will be shut down.
1184 .Ss "Starting the Jail"
1185 You are now ready to restart the jail and bring up the environment with
1186 all of its daemons and other programs.
1187 Create an entry for the jail in
1188 .Pa /etc/jail.conf :
1189 .Bd -literal -offset indent
1191 path = /tmp/jail/testjail;
1193 host.hostname = testhostname;
1194 ip4.addr = 192.0.2.100;
1196 exec.start = "/bin/sh /etc/rc";
1197 exec.stop = "/bin/sh /etc/rc.shutdown jail";
1201 To start a virtual server environment,
1203 is run to launch various daemons and services, and
1204 .Pa /etc/rc.shutdown
1205 is run to shut them down when the jail is removed.
1206 If you are running a single application in the jail,
1207 substitute the command used to start the application for
1208 .Dq /bin/sh /etc/rc ;
1209 there may be some script available to cleanly shut down the application,
1210 or it may be sufficient to go without a stop command, and have
1216 Start the jail by running:
1217 .Bd -literal -offset indent
1221 A few warnings may be produced; however, it should all work properly.
1222 You should be able to see
1225 and other processes running within the jail using
1229 flag appearing beside jailed processes.
1230 To see an active list of jails, use
1234 is enabled in the jail environment, you should be able to
1236 to the hostname or IP address of the jailed environment, and log
1237 in using the accounts you created previously.
1239 It is possible to have jails started at boot time.
1244 for more information.
1245 .Ss "Managing the Jail"
1246 Normal machine shutdown commands, such as
1251 cannot be used successfully within the jail.
1252 To kill all processes from within a jail, you may use one of the
1253 following commands, depending on what you want to accomplish:
1254 .Bd -literal -offset indent
1263 signals to all processes in the jail \(em be careful not to run this from
1264 the host environment!
1265 Once all of the jail's processes have died, unless the jail was created
1268 parameter, the jail will be removed.
1270 the intended use of the jail, you may also want to run
1271 .Pa /etc/rc.shutdown
1272 from within the jail.
1274 To shut down the jail from the outside, simply remove it with:
1275 .Bd -literal -offset indent
1279 which will run any commands specified by
1285 to any remaining jailed processes.
1288 .Pa /proc/ Ns Ar pid Ns Pa /status
1289 file contains, as its last field, the name of the jail in which the
1292 to indicate that the process is not running within a jail.
1295 command also shows a
1297 flag for processes in a jail.
1299 You can also list/kill processes based on their jail ID.
1300 To show processes and their jail ID, use the following command:
1302 .Dl "ps ax -o pid,jid,args"
1304 To show and then kill processes in jail number 3 use the following commands:
1305 .Bd -literal -offset indent
1312 .Ss "Jails and File Systems"
1313 It is not possible to
1317 any file system inside a jail unless the file system is marked
1318 jail-friendly, the jail's
1320 parameter is set, and the jail's
1322 parameter is lower than 2.
1324 Multiple jails sharing the same file system can influence each other.
1325 For example, a user in one jail can fill the file system,
1326 leaving no space for processes in the other jail.
1329 to prevent this will not work either, as the file system quotas
1330 are not aware of jails but only look at the user and group IDs.
1331 This means the same user ID in two jails share a single file
1333 One would need to use one file system per jail to make this work.
1334 .Ss "Sysctl MIB Entries"
1336 .Va security.jail.jailed
1337 can be used to determine if a process is running inside a jail (value
1338 is one) or not (value is zero).
1341 .Va security.jail.jail_max_af_ips
1342 determines how may address per address family a jail may have.
1345 Some MIB variables have per-jail settings.
1346 Changes to these variables by a jailed process do not affect the host
1347 environment, only the jail environment.
1349 .Va kern.securelevel ,
1350 .Va security.bsd.suser_enabled ,
1352 .Va kern.domainname ,
1356 .Ss "Hierarchical Jails"
1359 parameter, processes within a jail may be able to create jails of their own.
1360 These child jails are kept in a hierarchy, with jails only able to see and/or
1361 modify the jails they created (or those jails' children).
1362 Each jail has a read-only
1364 parameter, containing the
1366 of the jail that created it; a
1368 of 0 indicates the jail is a child of the current jail (or is a top-level
1369 jail if the current process isn't jailed).
1371 Jailed processes are not allowed to confer greater permissions than they
1372 themselves are given, e.g., if a jail is created with
1374 it is not able to create a jail with
1377 Similarly, such restrictions as
1381 may not be bypassed in child jails.
1383 A child jail may in turn create its own child jails if its own
1385 parameter is set (remember it is zero by default).
1386 These jails are visible to and can be modified by their parent and all
1389 Jail names reflect this hierarchy, with a full name being an MIB-type string
1391 For example, if a base system process creates a jail
1393 and a process under that jail creates another jail
1395 then the second jail will be seen as
1397 in the base system (though it is only seen as
1399 to any processes inside jail
1401 Jids on the other hand exist in a single space, and each jail must have a
1404 Like the names, a child jail's
1406 appears relative to its creator's own
1408 This is by virtue of the child jail being created in the chrooted
1409 environment of the first jail.
1453 Hierarchical/extensible jails were introduced in
1455 The configuration file was introduced in
1459 The jail feature was written by
1460 .An Poul-Henning Kamp
1462 who contributed it to
1466 wrote the extended documentation, found a few bugs, added
1467 a few new features, and cleaned up the userland jail environment.
1470 added multi-IP jail support for IPv4 and IPv6 based on a patch
1472 .An Pawel Jakub Dawidek
1476 added the extensible jail parameters, hierarchical jails,
1477 and the configuration file.
1479 It might be a good idea to add an
1480 address alias flag such that daemons listening on all IPs
1482 will not bind on that address, which would facilitate building a safe
1483 host environment such that host daemons do not impose on services offered
1485 Currently, the simplest answer is to minimize services
1486 offered on the host, possibly limiting it to services offered from
1488 which is easily configurable.
1490 Great care should be taken when managing directories visible within the jail.
1491 For example, if a jailed process has its current working directory set to a
1492 directory that is moved out of the jail's chroot, then the process may gain
1493 access to the file space outside of the jail.
1494 It is recommended that directories always be copied, rather than moved, out
1497 In addition, there are several ways in which an unprivileged user
1498 outside the jail can cooperate with a privileged user inside the jail
1499 and thereby obtain elevated privileges in the host environment.
1500 Most of these attacks can be mitigated by ensuring that the jail root
1501 is not accessible to unprivileged users in the host environment.
1502 Regardless, as a general rule, untrusted users with privileged access
1503 to a jail should not be given access to the host environment.