xref: /freebsd/usr.sbin/jail/jail.8 (revision 77a1348b3c1cfe8547be49a121b56299a1e18b69)
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2.\" Copyright (c) 2008-2012 James Gritton
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26.\" $FreeBSD$
27.\"
28.Dd August 6, 2019
29.Dt JAIL 8
30.Os
31.Sh NAME
32.Nm jail
33.Nd "manage system jails"
34.Sh SYNOPSIS
35.Nm
36.Op Fl dhilqv
37.Op Fl J Ar jid_file
38.Op Fl u Ar username
39.Op Fl U Ar username
40.Op Fl cmr
41.Ar param Ns = Ns Ar value ...
42.Op Cm command Ns = Ns Ar command ...
43.Nm
44.Op Fl dqv
45.Op Fl f Ar conf_file
46.Op Fl p Ar limit
47.Op Fl cmr
48.Op Ar jail
49.Nm
50.Op Fl qv
51.Op Fl f Ar conf_file
52.Op Fl e Ar separator
53.Op Fl rR
54.Op Cm * | Ar jail ...
55.Nm
56.Op Fl dhilqv
57.Op Fl J Ar jid_file
58.Op Fl u Ar username
59.Op Fl U Ar username
60.Op Fl n Ar jailname
61.Op Fl s Ar securelevel
62.Op Ar path hostname [ Ar ip Ns [ Ns Ar ,... Ns ]] Ar command ...
63.Sh DESCRIPTION
64The
65.Nm
66utility creates new jails, or modifies or removes existing jails.
67It can also print a list of configured jails and their parameters.
68A jail
69.Pq or Dq prison
70is specified via parameters on the command line, or in the
71.Xr jail.conf 5
72file.
73.Pp
74At least one of the options
75.Fl c ,
76.Fl e ,
77.Fl m
78or
79.Fl r
80must be specified.
81These options are used alone or in combination to describe the operation to
82perform:
83.Bl -tag -width indent
84.It Fl c
85Create a new jail.
86The jail
87.Va jid
88and
89.Va name
90parameters (if specified on the command line)
91must not refer to an existing jail.
92.It Fl e Ar separator
93Exhibit a list of all configured non-wildcard jails and their parameters.
94No jail creation, modification or removal performed if this option is used.
95The
96.Ar separator
97string is used to separate parameters.
98Use
99.Xr jls 8
100utility to list running jails.
101.It Fl m
102Modify an existing jail.
103One of the
104.Va jid
105or
106.Va name
107parameters must exist and refer to an existing jail.
108Some parameters may not be changed on a running jail.
109.It Fl r
110Remove the
111.Ar jail
112specified by jid or name.
113All jailed processes are killed, and all jails that are
114children of this jail are also
115removed.
116.It Fl rc
117Restart an existing jail.
118The jail is first removed and then re-created, as if
119.Dq Nm Fl r
120and
121.Dq Nm Fl c
122were run in succession.
123.It Fl cm
124Create a jail if it does not exist, or modify the jail if it does exist.
125.It Fl mr
126Modify an existing jail.
127The jail may be restarted if necessary to modify parameters than could
128not otherwise be changed.
129.It Fl cmr
130Create a jail if it doesn't exist, or modify (and possibly restart) the
131jail if it does exist.
132.El
133.Pp
134Other available options are:
135.Bl -tag -width indent
136.It Fl d
137Allow making changes to a dying jail, equivalent to the
138.Va allow.dying
139parameter.
140.It Fl f Ar conf_file
141Use configuration file
142.Ar conf_file
143instead of the default
144.Pa /etc/jail.conf .
145.It Fl h
146Resolve the
147.Va host.hostname
148parameter (or
149.Va hostname )
150and add all IP addresses returned by the resolver
151to the list of addresses for this jail.
152This is equivalent to the
153.Va ip_hostname
154parameter.
155.It Fl i
156Output (only) the jail identifier of the newly created jail(s).
157This implies the
158.Fl q
159option.
160.It Fl J Ar jid_file
161Write a
162.Ar jid_file
163file, containing the parameters used to start the jail.
164.It Fl l
165Run commands in a clean environment.
166This is deprecated and is equivalent to the exec.clean parameter.
167.It Fl n Ar jailname
168Set the jail's name.
169This is deprecated and is equivalent to the
170.Va name
171parameter.
172.It Fl p Ar limit
173Limit the number of commands from
174.Va  exec.*
175that can run simultaneously.
176.It Fl q
177Suppress the message printed whenever a jail is created, modified or removed.
178Only error messages will be printed.
179.It Fl R
180A variation of the
181.Fl r
182option that removes an existing jail without using the configuration file.
183No removal-related parameters for this jail will be used \(em the jail will
184simply be removed.
185.It Fl s Ar securelevel
186Set the
187.Va kern.securelevel
188MIB entry to the specified value inside the newly created jail.
189This is deprecated and is equivalent to the
190.Va securelevel
191parameter.
192.It Fl u Ar username
193The user name from host environment as whom jailed commands should run.
194This is deprecated and is equivalent to the
195.Va exec.jail_user
196and
197.Va exec.system_jail_user
198parameters.
199.It Fl U Ar username
200The user name from the jailed environment as whom jailed commands should run.
201This is deprecated and is equivalent to the
202.Va exec.jail_user
203parameter.
204.It Fl v
205Print a message on every operation, such as running commands and
206mounting filesystems.
207.El
208.Pp
209If no arguments are given after the options, the operation (except
210remove) will be performed on all jails specified in the
211.Xr jail.conf 5
212file.
213A single argument of a jail name will operate only on the specified jail.
214The
215.Fl r
216and
217.Fl R
218options can also remove running jails that aren't in the
219.Xr jail.conf 5
220file, specified by name or jid.
221.Pp
222An argument of
223.Dq *
224is a wildcard that will operate on all jails, regardless of whether
225they appear in
226.Xr jail.conf 5 ;
227this is the surest way for
228.Fl r
229to remove all jails.
230If hierarchical jails exist, a partial-matching wildcard definition may
231be specified.
232For example, an argument of
233.Dq foo.*
234would apply to jails with names like
235.Dq foo.bar
236and
237.Dq foo.bar.baz .
238.Pp
239A jail may be specified with parameters directly on the command line.
240In this case, the
241.Xr jail.conf 5
242file will not be used.
243For backward compatibility, the command line may also have four fixed
244parameters, without names:
245.Ar path ,
246.Ar hostname ,
247.Ar ip ,
248and
249.Ar command .
250This mode will always create a new jail, and the
251.Fl c
252and
253.Fl m
254options do not apply (and must not be present).
255.Ss Jail Parameters
256Parameters in the
257.Xr jail.conf 5
258file, or on the command line, are generally of the form
259.Dq name=value .
260Some parameters are boolean, and do not have a value but are set by the
261name alone with or without a
262.Dq no
263prefix, e.g.
264.Va persist
265or
266.Va nopersist .
267They can also be given the values
268.Dq true
269and
270.Dq false .
271Other parameters may have more than one value, specified as a
272comma-separated list or with
273.Dq +=
274in the configuration file (see
275.Xr jail.conf 5
276for details).
277.Pp
278The
279.Nm
280utility recognizes two classes of parameters.
281There are the true jail
282parameters that are passed to the kernel when the jail is created,
283which can be seen with
284.Xr jls 8 ,
285and can (usually) be changed with
286.Dq Nm Fl m .
287Then there are pseudo-parameters that are only used by
288.Nm
289itself.
290.Pp
291Jails have a set of core parameters, and kernel modules can add their own
292jail parameters.
293The current set of available parameters can be retrieved via
294.Dq Nm sysctl Fl d Va security.jail.param .
295Any parameters not set will be given default values, often based on the
296current environment.
297The core parameters are:
298.Bl -tag -width indent
299.It Va jid
300The jail identifier.
301This will be assigned automatically to a new jail (or can be explicitly
302set), and can be used to identify the jail for later modification, or
303for such commands as
304.Xr jls 8
305or
306.Xr jexec 8 .
307.It Va name
308The jail name.
309This is an arbitrary string that identifies a jail (except it may not
310contain a
311.Sq \&. ) .
312Like the
313.Va jid ,
314it can be passed to later
315.Nm
316commands, or to
317.Xr jls 8
318or
319.Xr jexec 8 .
320If no
321.Va name
322is supplied, a default is assumed that is the same as the
323.Va jid .
324The
325.Va name
326parameter is implied by the
327.Xr jail.conf 5
328file format, and need not be explicitly set when using the configuration
329file.
330.It Va path
331The directory which is to be the root of the jail.
332Any commands run inside the jail, either by
333.Nm
334or from
335.Xr jexec 8 ,
336are run from this directory.
337.It Va ip4.addr
338A list of IPv4 addresses assigned to the jail.
339If this is set, the jail is restricted to using only these addresses.
340Any attempts to use other addresses fail, and attempts to use wildcard
341addresses silently use the jailed address instead.
342For IPv4 the first address given will be used as the source address
343when source address selection on unbound sockets cannot find a better
344match.
345It is only possible to start multiple jails with the same IP address
346if none of the jails has more than this single overlapping IP address
347assigned to itself.
348.It Va ip4.saddrsel
349A boolean option to change the formerly mentioned behaviour and disable
350IPv4 source address selection for the jail in favour of the primary
351IPv4 address of the jail.
352Source address selection is enabled by default for all jails and the
353.Va ip4.nosaddrsel
354setting of a parent jail is not inherited for any child jails.
355.It Va ip4
356Control the availability of IPv4 addresses.
357Possible values are
358.Dq inherit
359to allow unrestricted access to all system addresses,
360.Dq new
361to restrict addresses via
362.Va ip4.addr ,
363and
364.Dq disable
365to stop the jail from using IPv4 entirely.
366Setting the
367.Va ip4.addr
368parameter implies a value of
369.Dq new .
370.It Va ip6.addr , Va ip6.saddrsel , Va ip6
371A set of IPv6 options for the jail, the counterparts to
372.Va ip4.addr ,
373.Va ip4.saddrsel
374and
375.Va ip4
376above.
377.It Va vnet
378Create the jail with its own virtual network stack,
379with its own network interfaces, addresses, routing table, etc.
380The kernel must have been compiled with the
381.Sy VIMAGE option
382for this to be available.
383Possible values are
384.Dq inherit
385to use the system network stack, possibly with restricted IP addresses,
386and
387.Dq new
388to create a new network stack.
389.It Va host.hostname
390The hostname of the jail.
391Other similar parameters are
392.Va host.domainname ,
393.Va host.hostuuid
394and
395.Va host.hostid .
396.It Va host
397Set the origin of hostname and related information.
398Possible values are
399.Dq inherit
400to use the system information and
401.Dq new
402for the jail to use the information from the above fields.
403Setting any of the above fields implies a value of
404.Dq new .
405.It Va securelevel
406The value of the jail's
407.Va kern.securelevel
408sysctl.
409A jail never has a lower securelevel than its parent system, but by
410setting this parameter it may have a higher one.
411If the system securelevel is changed, any jail securelevels will be at
412least as secure.
413.It Va devfs_ruleset
414The number of the devfs ruleset that is enforced for mounting devfs in
415this jail.
416A value of zero (default) means no ruleset is enforced.
417Descendant jails inherit the parent jail's devfs ruleset enforcement.
418Mounting devfs inside a jail is possible only if the
419.Va allow.mount
420and
421.Va allow.mount.devfs
422permissions are effective and
423.Va enforce_statfs
424is set to a value lower than 2.
425Devfs rules and rulesets cannot be viewed or modified from inside a jail.
426.Pp
427NOTE: It is important that only appropriate device nodes in devfs be
428exposed to a jail; access to disk devices in the jail may permit processes
429in the jail to bypass the jail sandboxing by modifying files outside of
430the jail.
431See
432.Xr devfs 8
433for information on how to use devfs rules to limit access to entries
434in the per-jail devfs.
435A simple devfs ruleset for jails is available as ruleset #4 in
436.Pa /etc/defaults/devfs.rules .
437.It Va children.max
438The number of child jails allowed to be created by this jail (or by
439other jails under this jail).
440This limit is zero by default, indicating the jail is not allowed to
441create child jails.
442See the
443.Sx "Hierarchical Jails"
444section for more information.
445.It Va children.cur
446The number of descendants of this jail, including its own child jails
447and any jails created under them.
448.It Va enforce_statfs
449This determines what information processes in a jail are able to get
450about mount points.
451It affects the behaviour of the following syscalls:
452.Xr statfs 2 ,
453.Xr fstatfs 2 ,
454.Xr getfsstat 2 ,
455and
456.Xr fhstatfs 2
457(as well as similar compatibility syscalls).
458When set to 0, all mount points are available without any restrictions.
459When set to 1, only mount points below the jail's chroot directory are
460visible.
461In addition to that, the path to the jail's chroot directory is removed
462from the front of their pathnames.
463When set to 2 (default), above syscalls can operate only on a mount-point
464where the jail's chroot directory is located.
465.It Va persist
466Setting this boolean parameter allows a jail to exist without any
467processes.
468Normally, a command is run as part of jail creation, and then the jail
469is destroyed as its last process exits.
470A new jail must have either the
471.Va persist
472parameter or
473.Va exec.start
474or
475.Va command
476pseudo-parameter set.
477.It Va cpuset.id
478The ID of the cpuset associated with this jail (read-only).
479.It Va dying
480This is true if the jail is in the process of shutting down (read-only).
481.It Va parent
482The
483.Va jid
484of the parent of this jail, or zero if this is a top-level jail
485(read-only).
486.It Va osrelease
487The string for the jail's
488.Va kern.osrelease
489sysctl and uname -r.
490.It Va osreldate
491The number for the jail's
492.Va kern.osreldate
493and uname -K.
494.It Va allow.*
495Some restrictions of the jail environment may be set on a per-jail
496basis.
497With the exception of
498.Va allow.set_hostname
499and
500.Va allow.reserved_ports ,
501these boolean parameters are off by default.
502.Bl -tag -width indent
503.It Va allow.set_hostname
504The jail's hostname may be changed via
505.Xr hostname 1
506or
507.Xr sethostname 3 .
508.It Va allow.sysvipc
509A process within the jail has access to System V IPC primitives.
510This is deprecated in favor of the per-module parameters (see below).
511When this parameter is set, it is equivalent to setting
512.Va sysvmsg ,
513.Va sysvsem ,
514and
515.Va sysvshm
516all to
517.Dq inherit .
518.It Va allow.raw_sockets
519The jail root is allowed to create raw sockets.
520Setting this parameter allows utilities like
521.Xr ping 8
522and
523.Xr traceroute 8
524to operate inside the jail.
525If this is set, the source IP addresses are enforced to comply
526with the IP address bound to the jail, regardless of whether or not
527the
528.Dv IP_HDRINCL
529flag has been set on the socket.
530Since raw sockets can be used to configure and interact with various
531network subsystems, extra caution should be used where privileged access
532to jails is given out to untrusted parties.
533.It Va allow.chflags
534Normally, privileged users inside a jail are treated as unprivileged by
535.Xr chflags 2 .
536When this parameter is set, such users are treated as privileged, and
537may manipulate system file flags subject to the usual constraints on
538.Va kern.securelevel .
539.It Va allow.mount
540privileged users inside the jail will be able to mount and unmount file
541system types marked as jail-friendly.
542The
543.Xr lsvfs 1
544command can be used to find file system types available for mount from
545within a jail.
546This permission is effective only if
547.Va enforce_statfs
548is set to a value lower than 2.
549.It Va allow.mount.devfs
550privileged users inside the jail will be able to mount and unmount the
551devfs file system.
552This permission is effective only together with
553.Va allow.mount
554and only when
555.Va enforce_statfs
556is set to a value lower than 2.
557The devfs ruleset should be restricted from the default by using the
558.Va devfs_ruleset
559option.
560.It Va allow.quotas
561The jail root may administer quotas on the jail's filesystem(s).
562This includes filesystems that the jail may share with other jails or
563with non-jailed parts of the system.
564.It Va allow.read_msgbuf
565Jailed users may read the kernel message buffer.
566If the
567.Va security.bsd.unprivileged_read_msgbuf
568MIB entry is zero, this will be restricted to the root user.
569.It Va allow.socket_af
570Sockets within a jail are normally restricted to IPv4, IPv6, local
571(UNIX), and route.  This allows access to other protocol stacks that
572have not had jail functionality added to them.
573.It Va allow.mlock
574Locking or unlocking physical pages in memory are normally not available
575within a jail.
576When this parameter is set, users may
577.Xr mlock 2
578or
579.Xr munlock 2
580memory subject to
581.Va security.bsd.unprivileged_mlock
582and resource limits.
583.It Va allow.reserved_ports
584The jail root may bind to ports lower than 1024.
585.It Va allow.unprivileged_proc_debug
586Unprivileged processes in the jail may use debugging facilities.
587.El
588.El
589.Pp
590Kernel modules may add their own parameters, which only exist when the
591module is loaded.
592These are typically headed under a parameter named after the module,
593with values of
594.Dq inherit
595to give the jail full use of the module,
596.Dq new
597to encapsulate the jail in some module-specific way,
598and
599.Dq disable
600to make the module unavailable to the jail.
601There also may be other parameters to define jail behavior within the module.
602Module-specific parameters include:
603.Bl -tag -width indent
604.It Va allow.mount.fdescfs
605privileged users inside the jail will be able to mount and unmount the
606fdescfs file system.
607This permission is effective only together with
608.Va allow.mount
609and only when
610.Va enforce_statfs
611is set to a value lower than 2.
612.It Va allow.mount.fusefs
613privileged users inside the jail will be able to mount and unmount
614fuse-based file systems.
615This permission is effective only together with
616.Va allow.mount
617and only when
618.Va enforce_statfs
619is set to a value lower than 2.
620.It Va allow.mount.nullfs
621privileged users inside the jail will be able to mount and unmount the
622nullfs file system.
623This permission is effective only together with
624.Va allow.mount
625and only when
626.Va enforce_statfs
627is set to a value lower than 2.
628.It Va allow.mount.procfs
629privileged users inside the jail will be able to mount and unmount the
630procfs file system.
631This permission is effective only together with
632.Va allow.mount
633and only when
634.Va enforce_statfs
635is set to a value lower than 2.
636.It Va allow.mount.linprocfs
637privileged users inside the jail will be able to mount and unmount the
638linprocfs file system.
639This permission is effective only together with
640.Va allow.mount
641and only when
642.Va enforce_statfs
643is set to a value lower than 2.
644.It Va allow.mount.linsysfs
645privileged users inside the jail will be able to mount and unmount the
646linsysfs file system.
647This permission is effective only together with
648.Va allow.mount
649and only when
650.Va enforce_statfs
651is set to a value lower than 2.
652.It Va allow.mount.tmpfs
653privileged users inside the jail will be able to mount and unmount the
654tmpfs file system.
655This permission is effective only together with
656.Va allow.mount
657and only when
658.Va enforce_statfs
659is set to a value lower than 2.
660.It Va allow.mount.zfs
661privileged users inside the jail will be able to mount and unmount the
662ZFS file system.
663This permission is effective only together with
664.Va allow.mount
665and only when
666.Va enforce_statfs
667is set to a value lower than 2.
668See
669.Xr zfs 8
670for information on how to configure the ZFS filesystem to operate from
671within a jail.
672.It Va allow.vmm
673The jail may access
674.Xr vmm 4 .
675This flag is only available when the
676.Xr vmm 4
677kernel module is loaded.
678.It Va linux
679Determine how a jail's Linux emulation environment appears.
680A value of
681.Dq inherit
682will keep the same environment, and
683.Dq new
684will give the jail its own environment (still originally inherited when
685the jail is created).
686.It Va linux.osname , linux.osrelease , linux.oss_version
687The Linux OS name, OS release, and OSS version associated with this jail.
688.It Va sysvmsg
689Allow access to SYSV IPC message primitives.
690If set to
691.Dq inherit ,
692all IPC objects on the system are visible to this jail, whether they
693were created by the jail itself, the base system, or other jails.
694If set to
695.Dq new ,
696the jail will have its own key namespace, and can only see the objects
697that it has created;
698the system (or parent jail) has access to the jail's objects, but not to
699its keys.
700If set to
701.Dq disable ,
702the jail cannot perform any sysvmsg-related system calls.
703.It Va sysvsem, sysvshm
704Allow access to SYSV IPC semaphore and shared memory primitives, in the
705same manner as
706.Va sysvmsg.
707.El
708.Pp
709There are pseudo-parameters that are not passed to the kernel, but are
710used by
711.Nm
712to set up the jail environment, often by running specified commands
713when jails are created or removed.
714The
715.Va exec.*
716command parameters are
717.Xr sh 1
718command lines that are run in either the system or jail environment.
719They may be given multiple values, which would run the specified
720commands in sequence.
721All commands must succeed (return a zero exit status), or the jail will
722not be created or removed, as appropriate.
723.Pp
724The pseudo-parameters are:
725.Bl -tag -width indent
726.It Va exec.prestart
727Command(s) to run in the system environment before a jail is created.
728.It Va exec.created
729Command(s) to run in the system environment right after a jail has been
730created, but before commands (or services) get executed in the jail.
731.It Va exec.start
732Command(s) to run in the jail environment when a jail is created.
733A typical command to run is
734.Dq sh /etc/rc .
735.It Va command
736A synonym for
737.Va exec.start
738for use when specifying a jail directly on the command line.
739Unlike other parameters whose value is a single string,
740.Va command
741uses the remainder of the
742.Nm
743command line as its own arguments.
744.It Va exec.poststart
745Command(s) to run in the system environment after a jail is created,
746and after any
747.Va exec.start
748commands have completed.
749.It Va exec.prestop
750Command(s) to run in the system environment before a jail is removed.
751.It Va exec.stop
752Command(s) to run in the jail environment before a jail is removed,
753and after any
754.Va exec.prestop
755commands have completed.
756A typical command to run is
757.Dq sh /etc/rc.shutdown jail .
758.It Va exec.poststop
759Command(s) to run in the system environment after a jail is removed.
760.It Va exec.clean
761Run commands in a clean environment.
762The environment is discarded except for
763.Ev HOME , SHELL , TERM
764and
765.Ev USER .
766.Ev HOME
767and
768.Ev SHELL
769are set to the target login's default values.
770.Ev USER
771is set to the target login.
772.Ev TERM
773is imported from the current environment.
774The environment variables from the login class capability database for the
775target login are also set.
776.It Va exec.jail_user
777The user to run commands as, when running in the jail environment.
778The default is to run the commands as the current user.
779.It Va exec.system_jail_user
780This boolean option looks for the
781.Va exec.jail_user
782in the system
783.Xr passwd 5
784file, instead of in the jail's file.
785.It Va exec.system_user
786The user to run commands as, when running in the system environment.
787The default is to run the commands as the current user.
788.It Va exec.timeout
789The maximum amount of time to wait for a command to complete, in
790seconds.
791If a command is still running after this timeout has passed,
792the jail will not be created or removed, as appropriate.
793.It Va exec.consolelog
794A file to direct command output (stdout and stderr) to.
795.It Va exec.fib
796The FIB (routing table) to set when running commands inside the jail.
797.It Va stop.timeout
798The maximum amount of time to wait for a jail's processes to exit
799after sending them a
800.Dv SIGTERM
801signal (which happens after the
802.Va exec.stop
803commands have completed).
804After this many seconds have passed, the jail will be removed, which
805will kill any remaining processes.
806If this is set to zero, no
807.Dv SIGTERM
808is sent and the jail is immediately removed.
809The default is 10 seconds.
810.It Va interface
811A network interface to add the jail's IP addresses
812.Va ( ip4.addr
813and
814.Va ip6.addr )
815to.
816An alias for each address will be added to the interface before the
817jail is created, and will be removed from the interface after the
818jail is removed.
819.It Va ip4.addr
820In addition to the IP addresses that are passed to the kernel, an
821interface, netmask and additional parameters (as supported by
822.Xr ifconfig 8 Ns )
823may also be specified, in the form
824.Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
825If an interface is given before the IP address, an alias for the address
826will be added to that interface, as it is with the
827.Va interface
828parameter.
829If a netmask in either dotted-quad or CIDR form is given
830after an IP address, it will be used when adding the IP alias.
831If additional parameters are specified then they will also be used when
832adding the IP alias.
833.It Va ip6.addr
834In addition to the IP addresses that are passed to the kernel,
835an interface, prefix and additional parameters (as supported by
836.Xr ifconfig 8 Ns )
837may also be specified, in the form
838.Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
839.It Va vnet.interface
840A network interface to give to a vnet-enabled jail after is it created.
841The interface will automatically be released when the jail is removed.
842.It Va ip_hostname
843Resolve the
844.Va host.hostname
845parameter and add all IP addresses returned by the resolver
846to the list of addresses
847.Po Va ip4.addr
848or
849.Va ip6.addr Pc
850for this jail.
851This may affect default address selection for outgoing IPv4 connections
852from jails.
853The address first returned by the resolver for each address family
854will be used as the primary address.
855.It Va mount
856A filesystem to mount before creating the jail (and to unmount after
857removing it), given as a single
858.Xr fstab 5
859line.
860.It Va mount.fstab
861An
862.Xr fstab 5
863format file containing filesystems to mount before creating a jail.
864.It Va mount.devfs
865Mount a
866.Xr devfs 5
867filesystem on the chrooted
868.Pa /dev
869directory, and apply the ruleset in the
870.Va devfs_ruleset
871parameter (or a default of ruleset 4: devfsrules_jail)
872to restrict the devices visible inside the jail.
873.It Va mount.fdescfs
874Mount a
875.Xr fdescfs 5
876filesystem on the chrooted
877.Pa /dev/fd
878directory.
879.It Va mount.procfs
880Mount a
881.Xr procfs 5
882filesystem on the chrooted
883.Pa /proc
884directory.
885.It Va allow.dying
886Allow making changes to a
887.Va dying
888jail.
889.It Va depend
890Specify a jail (or jails) that this jail depends on.
891When this jail is to be created, any jail(s) it depends on must already exist.
892If not, they will be created automatically, up to the completion of the last
893.Va exec.poststart
894command, before any action will taken to create this jail.
895When jails are removed the opposite is true:
896this jail will be removed, up to the last
897.Va exec.poststop
898command, before any jail(s) it depends on are stopped.
899.El
900.Sh EXAMPLES
901Jails are typically set up using one of two philosophies: either to
902constrain a specific application (possibly running with privilege), or
903to create a
904.Dq "virtual system image"
905running a variety of daemons and services.
906In both cases, a fairly complete file system install of
907.Fx
908is
909required, so as to provide the necessary command line tools, daemons,
910libraries, application configuration files, etc.
911However, for a virtual server configuration, a fair amount of
912additional work is required so as to replace the
913.Dq boot
914process.
915This manual page documents the configuration steps necessary to support
916either of these steps, although the configuration steps may need to be
917refined based on local requirements.
918.Ss "Setting up a Jail Directory Tree"
919To set up a jail directory tree containing an entire
920.Fx
921distribution, the following
922.Xr sh 1
923command script can be used:
924.Bd -literal
925D=/here/is/the/jail
926cd /usr/src
927mkdir -p $D
928make world DESTDIR=$D
929make distribution DESTDIR=$D
930.Ed
931.Pp
932In many cases this example would put far more in the jail than needed.
933In the other extreme case a jail might contain only one file:
934the executable to be run in the jail.
935.Pp
936We recommend experimentation, and caution that it is a lot easier to
937start with a
938.Dq fat
939jail and remove things until it stops working,
940than it is to start with a
941.Dq thin
942jail and add things until it works.
943.Ss "Setting Up a Jail"
944Do what was described in
945.Sx "Setting Up a Jail Directory Tree"
946to build the jail directory tree.
947For the sake of this example, we will
948assume you built it in
949.Pa /data/jail/testjail ,
950for a jail named
951.Dq testjail .
952Substitute below as needed with your
953own directory, IP address, and hostname.
954.Ss "Setting up the Host Environment"
955First, set up the real system's environment to be
956.Dq jail-friendly .
957For consistency, we will refer to the parent box as the
958.Dq "host environment" ,
959and to the jailed virtual machine as the
960.Dq "jail environment" .
961Since jails are implemented using IP aliases, one of the first things to do
962is to disable IP services on the host system that listen on all local
963IP addresses for a service.
964If a network service is present in the host environment that binds all
965available IP addresses rather than specific IP addresses, it may service
966requests sent to jail IP addresses if the jail did not bind the port.
967This means changing
968.Xr inetd 8
969to only listen on the
970appropriate IP address, and so forth.
971Add the following to
972.Pa /etc/rc.conf
973in the host environment:
974.Bd -literal -offset indent
975sendmail_enable="NO"
976inetd_flags="-wW -a 192.0.2.23"
977rpcbind_enable="NO"
978.Ed
979.Pp
980.Li 192.0.2.23
981is the native IP address for the host system, in this example.
982Daemons that run out of
983.Xr inetd 8
984can be easily configured to use only the specified host IP address.
985Other daemons
986will need to be manually configured \(em for some this is possible through
987.Xr rc.conf 5
988flags entries; for others it is necessary to modify per-application
989configuration files, or to recompile the application.
990The following frequently deployed services must have their individual
991configuration files modified to limit the application to listening
992to a specific IP address:
993.Pp
994To configure
995.Xr sshd 8 ,
996it is necessary to modify
997.Pa /etc/ssh/sshd_config .
998.Pp
999To configure
1000.Xr sendmail 8 ,
1001it is necessary to modify
1002.Pa /etc/mail/sendmail.cf .
1003.Pp
1004For
1005.Xr named 8 ,
1006it is necessary to modify
1007.Pa /etc/namedb/named.conf .
1008.Pp
1009In addition, a number of services must be recompiled in order to run
1010them in the host environment.
1011This includes most applications providing services using
1012.Xr rpc 3 ,
1013such as
1014.Xr rpcbind 8 ,
1015.Xr nfsd 8 ,
1016and
1017.Xr mountd 8 .
1018In general, applications for which it is not possible to specify which
1019IP address to bind should not be run in the host environment unless they
1020should also service requests sent to jail IP addresses.
1021Attempting to serve
1022NFS from the host environment may also cause confusion, and cannot be
1023easily reconfigured to use only specific IPs, as some NFS services are
1024hosted directly from the kernel.
1025Any third-party network software running
1026in the host environment should also be checked and configured so that it
1027does not bind all IP addresses, which would result in those services also
1028appearing to be offered by the jail environments.
1029.Pp
1030Once
1031these daemons have been disabled or fixed in the host environment, it is
1032best to reboot so that all daemons are in a known state, to reduce the
1033potential for confusion later (such as finding that when you send mail
1034to a jail, and its sendmail is down, the mail is delivered to the host,
1035etc.).
1036.Ss "Configuring the Jail"
1037Start any jail for the first time without configuring the network
1038interface so that you can clean it up a little and set up accounts.
1039As
1040with any machine (virtual or not), you will need to set a root password, time
1041zone, etc.
1042Some of these steps apply only if you intend to run a full virtual server
1043inside the jail; others apply both for constraining a particular application
1044or for running a virtual server.
1045.Pp
1046Start a shell in the jail:
1047.Bd -literal -offset indent
1048jail -c path=/data/jail/testjail mount.devfs \\
1049	host.hostname=testhostname ip4.addr=192.0.2.100 \\
1050	command=/bin/sh
1051.Ed
1052.Pp
1053Assuming no errors, you will end up with a shell prompt within the jail.
1054You can now run
1055.Xr bsdconfig 8
1056and do the post-install configuration to set various configuration options,
1057or perform these actions manually by editing
1058.Pa /etc/rc.conf ,
1059etc.
1060.Pp
1061.Bl -bullet -offset indent -compact
1062.It
1063Configure
1064.Pa /etc/resolv.conf
1065so that name resolution within the jail will work correctly.
1066.It
1067Run
1068.Xr newaliases 1
1069to quell
1070.Xr sendmail 8
1071warnings.
1072.It
1073Set a root password, probably different from the real host system.
1074.It
1075Set the timezone.
1076.It
1077Add accounts for users in the jail environment.
1078.It
1079Install any packages the environment requires.
1080.El
1081.Pp
1082You may also want to perform any package-specific configuration (web servers,
1083SSH servers, etc), patch up
1084.Pa /etc/syslog.conf
1085so it logs as you would like, etc.
1086If you are not using a virtual server, you may wish to modify
1087.Xr syslogd 8
1088in the host environment to listen on the syslog socket in the jail
1089environment; in this example, the syslog socket would be stored in
1090.Pa /data/jail/testjail/var/run/log .
1091.Pp
1092Exit from the shell, and the jail will be shut down.
1093.Ss "Starting the Jail"
1094You are now ready to restart the jail and bring up the environment with
1095all of its daemons and other programs.
1096Create an entry for the jail in
1097.Pa /etc/jail.conf :
1098.Bd -literal -offset indent
1099testjail {
1100	path = /tmp/jail/testjail;
1101	mount.devfs;
1102	host.hostname = testhostname;
1103	ip4.addr = 192.0.2.100;
1104	interface = em0;
1105	exec.start = "/bin/sh /etc/rc";
1106	exec.stop = "/bin/sh /etc/rc.shutdown jail";
1107}
1108.Ed
1109.Pp
1110To start a virtual server environment,
1111.Pa /etc/rc
1112is run to launch various daemons and services, and
1113.Pa /etc/rc.shutdown
1114is run to shut them down when the jail is removed.
1115If you are running a single application in the jail,
1116substitute the command used to start the application for
1117.Dq /bin/sh /etc/rc ;
1118there may be some script available to cleanly shut down the application,
1119or it may be sufficient to go without a stop command, and have
1120.Nm
1121send
1122.Dv SIGTERM
1123to the application.
1124.Pp
1125Start the jail by running:
1126.Bd -literal -offset indent
1127jail -c testjail
1128.Ed
1129.Pp
1130A few warnings may be produced; however, it should all work properly.
1131You should be able to see
1132.Xr inetd 8 ,
1133.Xr syslogd 8 ,
1134and other processes running within the jail using
1135.Xr ps 1 ,
1136with the
1137.Ql J
1138flag appearing beside jailed processes.
1139To see an active list of jails, use
1140.Xr jls 8 .
1141If
1142.Xr sshd 8
1143is enabled in the jail environment, you should be able to
1144.Xr ssh 1
1145to the hostname or IP address of the jailed environment, and log
1146in using the accounts you created previously.
1147.Pp
1148It is possible to have jails started at boot time.
1149Please refer to the
1150.Dq jail_*
1151variables in
1152.Xr rc.conf 5
1153for more information.
1154.Ss "Managing the Jail"
1155Normal machine shutdown commands, such as
1156.Xr halt 8 ,
1157.Xr reboot 8 ,
1158and
1159.Xr shutdown 8 ,
1160cannot be used successfully within the jail.
1161To kill all processes from within a jail, you may use one of the
1162following commands, depending on what you want to accomplish:
1163.Bd -literal -offset indent
1164kill -TERM -1
1165kill -KILL -1
1166.Ed
1167.Pp
1168This will send the
1169.Dv SIGTERM
1170or
1171.Dv SIGKILL
1172signals to all processes in the jail \(em be careful not to run this from
1173the host environment!
1174Once all of the jail's processes have died, unless the jail was created
1175with the
1176.Va persist
1177parameter, the jail will be removed.
1178Depending on
1179the intended use of the jail, you may also want to run
1180.Pa /etc/rc.shutdown
1181from within the jail.
1182.Pp
1183To shut down the jail from the outside, simply remove it with
1184.Nm
1185.Ar -r ,
1186which will run any commands specified by
1187.Va exec.stop ,
1188and then send
1189.Dv SIGTERM
1190and eventually
1191.Dv SIGKILL
1192to any remaining jailed processes.
1193.Pp
1194The
1195.Pa /proc/ Ns Ar pid Ns Pa /status
1196file contains, as its last field, the name of the jail in which the
1197process runs, or
1198.Dq Li -
1199to indicate that the process is not running within a jail.
1200The
1201.Xr ps 1
1202command also shows a
1203.Ql J
1204flag for processes in a jail.
1205.Pp
1206You can also list/kill processes based on their jail ID.
1207To show processes and their jail ID, use the following command:
1208.Pp
1209.Dl "ps ax -o pid,jid,args"
1210.Pp
1211To show and then kill processes in jail number 3 use the following commands:
1212.Bd -literal -offset indent
1213pgrep -lfj 3
1214pkill -j 3
1215.Ed
1216or:
1217.Pp
1218.Dl "killall -j 3"
1219.Ss "Jails and File Systems"
1220It is not possible to
1221.Xr mount 8
1222or
1223.Xr umount 8
1224any file system inside a jail unless the file system is marked
1225jail-friendly, the jail's
1226.Va allow.mount
1227parameter is set, and the jail's
1228.Va enforce_statfs
1229parameter is lower than 2.
1230.Pp
1231Multiple jails sharing the same file system can influence each other.
1232For example, a user in one jail can fill the file system,
1233leaving no space for processes in the other jail.
1234Trying to use
1235.Xr quota 1
1236to prevent this will not work either, as the file system quotas
1237are not aware of jails but only look at the user and group IDs.
1238This means the same user ID in two jails share a single file
1239system quota.
1240One would need to use one file system per jail to make this work.
1241.Ss "Sysctl MIB Entries"
1242The read-only entry
1243.Va security.jail.jailed
1244can be used to determine if a process is running inside a jail (value
1245is one) or not (value is zero).
1246.Pp
1247The variable
1248.Va security.jail.max_af_ips
1249determines how may address per address family a jail may have.
1250The default is 255.
1251.Pp
1252Some MIB variables have per-jail settings.
1253Changes to these variables by a jailed process do not affect the host
1254environment, only the jail environment.
1255These variables are
1256.Va kern.securelevel ,
1257.Va kern.hostname ,
1258.Va kern.domainname ,
1259.Va kern.hostid ,
1260and
1261.Va kern.hostuuid .
1262.Ss "Hierarchical Jails"
1263By setting a jail's
1264.Va children.max
1265parameter, processes within a jail may be able to create jails of their own.
1266These child jails are kept in a hierarchy, with jails only able to see and/or
1267modify the jails they created (or those jails' children).
1268Each jail has a read-only
1269.Va parent
1270parameter, containing the
1271.Va jid
1272of the jail that created it; a
1273.Va jid
1274of 0 indicates the jail is a child of the current jail (or is a top-level
1275jail if the current process isn't jailed).
1276.Pp
1277Jailed processes are not allowed to confer greater permissions than they
1278themselves are given, e.g., if a jail is created with
1279.Va allow.nomount ,
1280it is not able to create a jail with
1281.Va allow.mount
1282set.
1283Similarly, such restrictions as
1284.Va ip4.addr
1285and
1286.Va securelevel
1287may not be bypassed in child jails.
1288.Pp
1289A child jail may in turn create its own child jails if its own
1290.Va children.max
1291parameter is set (remember it is zero by default).
1292These jails are visible to and can be modified by their parent and all
1293ancestors.
1294.Pp
1295Jail names reflect this hierarchy, with a full name being an MIB-type string
1296separated by dots.
1297For example, if a base system process creates a jail
1298.Dq foo ,
1299and a process under that jail creates another jail
1300.Dq bar ,
1301then the second jail will be seen as
1302.Dq foo.bar
1303in the base system (though it is only seen as
1304.Dq bar
1305to any processes inside jail
1306.Dq foo ) .
1307Jids on the other hand exist in a single space, and each jail must have a
1308unique jid.
1309.Pp
1310Like the names, a child jail's
1311.Va path
1312appears relative to its creator's own
1313.Va path .
1314This is by virtue of the child jail being created in the chrooted
1315environment of the first jail.
1316.Sh SEE ALSO
1317.Xr killall 1 ,
1318.Xr lsvfs 1 ,
1319.Xr newaliases 1 ,
1320.Xr pgrep 1 ,
1321.Xr pkill 1 ,
1322.Xr ps 1 ,
1323.Xr quota 1 ,
1324.Xr jail_set 2 ,
1325.Xr vmm 4 ,
1326.Xr devfs 5 ,
1327.Xr fdescfs 5 ,
1328.Xr jail.conf 5 ,
1329.Xr linprocfs 5 ,
1330.Xr linsysfs 5 ,
1331.Xr procfs 5 ,
1332.Xr rc.conf 5 ,
1333.Xr sysctl.conf 5 ,
1334.Xr bsdconfig 8 ,
1335.Xr chroot 8 ,
1336.Xr devfs 8 ,
1337.Xr halt 8 ,
1338.Xr ifconfig 8 ,
1339.Xr inetd 8 ,
1340.Xr jexec 8 ,
1341.Xr jls 8 ,
1342.Xr mount 8 ,
1343.Xr named 8 ,
1344.Xr reboot 8 ,
1345.Xr rpcbind 8 ,
1346.Xr sendmail 8 ,
1347.Xr shutdown 8 ,
1348.Xr sysctl 8 ,
1349.Xr syslogd 8 ,
1350.Xr umount 8
1351.Sh HISTORY
1352The
1353.Nm
1354utility appeared in
1355.Fx 4.0 .
1356Hierarchical/extensible jails were introduced in
1357.Fx 8.0 .
1358The configuration file was introduced in
1359.Fx 9.1 .
1360.Sh AUTHORS
1361.An -nosplit
1362The jail feature was written by
1363.An Poul-Henning Kamp
1364for R&D Associates
1365who contributed it to
1366.Fx .
1367.Pp
1368.An Robert Watson
1369wrote the extended documentation, found a few bugs, added
1370a few new features, and cleaned up the userland jail environment.
1371.Pp
1372.An Bjoern A. Zeeb
1373added multi-IP jail support for IPv4 and IPv6 based on a patch
1374originally done by
1375.An Pawel Jakub Dawidek
1376for IPv4.
1377.Pp
1378.An James Gritton
1379added the extensible jail parameters, hierarchical jails,
1380and the configuration file.
1381.Sh BUGS
1382It might be a good idea to add an
1383address alias flag such that daemons listening on all IPs
1384.Pq Dv INADDR_ANY
1385will not bind on that address, which would facilitate building a safe
1386host environment such that host daemons do not impose on services offered
1387from within jails.
1388Currently, the simplest answer is to minimize services
1389offered on the host, possibly limiting it to services offered from
1390.Xr inetd 8
1391which is easily configurable.
1392.Sh NOTES
1393Great care should be taken when managing directories visible within the jail.
1394For example, if a jailed process has its current working directory set to a
1395directory that is moved out of the jail's chroot, then the process may gain
1396access to the file space outside of the jail.
1397It is recommended that directories always be copied, rather than moved, out
1398of a jail.
1399.Pp
1400In addition, there are several ways in which an unprivileged user
1401outside the jail can cooperate with a privileged user inside the jail
1402and thereby obtain elevated privileges in the host environment.
1403Most of these attacks can be mitigated by ensuring that the jail root
1404is not accessible to unprivileged users in the host environment.
1405Regardless, as a general rule, untrusted users with privileged access
1406to a jail should not be given access to the host environment.
1407