1 .\" Copyright (c) 2000, 2003 Robert N. M. Watson
2 .\" Copyright (c) 2008-2012 James Gritton
3 .\" All rights reserved.
5 .\" Redistribution and use in source and binary forms, with or without
6 .\" modification, are permitted provided that the following conditions
8 .\" 1. Redistributions of source code must retain the above copyright
9 .\" notice, this list of conditions and the following disclaimer.
10 .\" 2. Redistributions in binary form must reproduce the above copyright
11 .\" notice, this list of conditions and the following disclaimer in the
12 .\" documentation and/or other materials provided with the distribution.
14 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 .Op Ar path hostname [ Ar ip Ns [ Ns Ar ,... Ns ]] Ar command ...
65 utility creates new jails, or modifies or removes existing jails.
68 is specified via parameters on the command line, or in the
72 At least one of the options
78 These options are used alone or in combination to describe the operation to
80 .Bl -tag -width indent
87 parameters (if specified on the command line)
88 must not refer to an existing jail.
90 Modify an existing jail.
95 parameters must exist and refer to an existing jail.
96 Some parameters may not be changed on a running jail.
100 specified by jid or name.
101 All jailed processes are killed, and all jails that are
102 children of this jail are also
105 Restart an existing jail.
106 The jail is first removed and then re-created, as if
110 were run in succession.
112 Create a jail if it does not exist, or modify the jail if it does exist.
114 Modify an existing jail.
115 The jail may be restarted if necessary to modify parameters than could
116 not otherwise be changed.
118 Create a jail if it doesn't exist, or modify (and possibly restart) the
119 jail if it does exist.
122 Other available options are:
123 .Bl -tag -width indent
125 Allow making changes to a dying jail, equivalent to the
128 .It Fl f Ar conf_file
129 Use configuration file
131 instead of the default
138 and add all IP addresses returned by the resolver
139 to the list of addresses for this jail.
140 This is equivalent to the
144 Output (only) the jail identifier of the newly created jail(s).
151 file, containing the parameters used to start the jail.
153 Run commands in a clean environment.
154 This is deprecated and is equivalent to the exec.clean parameter.
157 This is deprecated and is equivalent to the
161 Limit the number of commands from
163 that can run simultaneously.
165 Suppress the message printed whenever a jail is created, modified or removed.
166 Only error messages will be printed.
170 option that removes an existing jail without using the configuration file.
171 No removal-related parameters for this jail will be used \(em the jail will
173 .It Fl s Ar securelevel
176 MIB entry to the specified value inside the newly created jail.
177 This is deprecated and is equivalent to the
181 The user name from host environment as whom jailed commands should run.
182 This is deprecated and is equivalent to the
185 .Va exec.system_jail_user
188 The user name from the jailed environment as whom jailed commands should run.
189 This is deprecated and is equivalent to the
193 Print a message on every operation, such as running commands and
194 mounting filesystems.
197 If no arguments are given after the options, the operation (except
198 remove) will be performed on all jails specified in the
201 A single argument of a jail name will operate only on the specified jail.
206 options can also remove running jails that aren't in the
208 file, specified by name or jid.
212 is a wildcard that will operate on all jails, regardless of whether
215 this is the surest way for
218 If hierarchical jails exist, a partial-matching wildcard definition may
220 For example, an argument of
222 would apply to jails with names like
227 A jail may be specified with parameters directly on the command line.
230 file will not be used.
231 For backward compatibility, the command line may also have four fixed
232 parameters, without names:
238 This mode will always create a new jail, and the
242 options do not apply (and must not be present).
246 file, or on the command line, are generally of the form
248 Some parameters are boolean, and do not have a value but are set by the
249 name alone with or without a
255 They can also be given the values
259 Other parameters may have more than one value, specified as a
260 comma-separated list or with
262 in the configuration file (see
268 utility recognizes two classes of parameters.
269 There are the true jail
270 parameters that are passed to the kernel when the jail is created,
271 which can be seen with
273 and can (usually) be changed with
275 Then there are pseudo-parameters that are only used by
279 Jails have a set a core parameters, and kernel modules can add their own
281 The current set of available parameters can be retrieved via
282 .Dq Nm sysctl Fl d Va security.jail.param .
283 Any parameters not set will be given default values, often based on the
285 The core parameters are:
286 .Bl -tag -width indent
289 This will be assigned automatically to a new jail (or can be explicitly
290 set), and can be used to identify the jail for later modification, or
297 This is an arbitrary string that identifies a jail (except it may not
302 it can be passed to later
310 is supplied, a default is assumed that is the same as the
314 parameter is implied by the
316 file format, and need not be explicitly set when using the configuration
319 The directory which is to be the root of the jail.
320 Any commands run inside the jail, either by
324 are run from this directory.
326 A list of IPv4 addresses assigned to the jail.
327 If this is set, the jail is restricted to using only these addresses.
328 Any attempts to use other addresses fail, and attempts to use wildcard
329 addresses silently use the jailed address instead.
330 For IPv4 the first address given will be used as the source address
331 when source address selection on unbound sockets cannot find a better
333 It is only possible to start multiple jails with the same IP address
334 if none of the jails has more than this single overlapping IP address
337 A boolean option to change the formerly mentioned behaviour and disable
338 IPv4 source address selection for the jail in favour of the primary
339 IPv4 address of the jail.
340 Source address selection is enabled by default for all jails and the
342 setting of a parent jail is not inherited for any child jails.
344 Control the availability of IPv4 addresses.
347 to allow unrestricted access to all system addresses,
349 to restrict addresses via
353 to stop the jail from using IPv4 entirely.
356 parameter implies a value of
358 .It Va ip6.addr , Va ip6.saddrsel , Va ip6
359 A set of IPv6 options for the jail, the counterparts to
366 Create the jail with its own virtual network stack,
367 with its own network interfaces, addresses, routing table, etc.
368 The kernel must have been compiled with the
370 for this to be available.
373 to use the system network stack, possibly with restricted IP addresses,
376 to create a new network stack.
378 The hostname of the jail.
379 Other similar parameters are
380 .Va host.domainname ,
385 Set the origin of hostname and related information.
388 to use the system information and
390 for the jail to use the information from the above fields.
391 Setting any of the above fields implies a value of
394 The value of the jail's
397 A jail never has a lower securelevel than its parent system, but by
398 setting this parameter it may have a higher one.
399 If the system securelevel is changed, any jail securelevels will be at
402 The number of the devfs ruleset that is enforced for mounting devfs in
404 A value of zero (default) means no ruleset is enforced.
405 Descendant jails inherit the parent jail's devfs ruleset enforcement.
406 Mounting devfs inside a jail is possible only if the
409 .Va allow.mount.devfs
410 permissions are effective and
412 is set to a value lower than 2.
413 Devfs rules and rulesets cannot be viewed or modified from inside a jail.
415 NOTE: It is important that only appropriate device nodes in devfs be
416 exposed to a jail; access to disk devices in the jail may permit processes
417 in the jail to bypass the jail sandboxing by modifying files outside of
421 for information on how to use devfs rules to limit access to entries
422 in the per-jail devfs.
423 A simple devfs ruleset for jails is available as ruleset #4 in
424 .Pa /etc/defaults/devfs.rules .
426 The number of child jails allowed to be created by this jail (or by
427 other jails under this jail).
428 This limit is zero by default, indicating the jail is not allowed to
431 .Sx "Hierarchical Jails"
432 section for more information.
434 The number of descendants of this jail, including its own child jails
435 and any jails created under them.
436 .It Va enforce_statfs
437 This determines what information processes in a jail are able to get
439 It affects the behaviour of the following syscalls:
445 (as well as similar compatibility syscalls).
446 When set to 0, all mount points are available without any restrictions.
447 When set to 1, only mount points below the jail's chroot directory are
449 In addition to that, the path to the jail's chroot directory is removed
450 from the front of their pathnames.
451 When set to 2 (default), above syscalls can operate only on a mount-point
452 where the jail's chroot directory is located.
454 Setting this boolean parameter allows a jail to exist without any
456 Normally, a command is run as part of jail creation, and then the jail
457 is destroyed as its last process exits.
458 A new jail must have either the
464 pseudo-parameter set.
466 The ID of the cpuset associated with this jail (read-only).
468 This is true if the jail is in the process of shutting down (read-only).
472 of the parent of this jail, or zero if this is a top-level jail
475 Some restrictions of the jail environment may be set on a per-jail
477 With the exception of
478 .Va allow.set_hostname ,
479 these boolean parameters are off by default.
480 .Bl -tag -width indent
481 .It Va allow.set_hostname
482 The jail's hostname may be changed via
487 A process within the jail has access to System V IPC primitives.
488 In the current jail implementation, System V primitives share a single
489 namespace across the host and jail environments, meaning that processes
490 within a jail would be able to communicate with (and potentially interfere
491 with) processes outside of the jail, and in other jails.
492 .It Va allow.raw_sockets
493 The jail root is allowed to create raw sockets.
494 Setting this parameter allows utilities like
498 to operate inside the jail.
499 If this is set, the source IP addresses are enforced to comply
500 with the IP address bound to the jail, regardless of whether or not
503 flag has been set on the socket.
504 Since raw sockets can be used to configure and interact with various
505 network subsystems, extra caution should be used where privileged access
506 to jails is given out to untrusted parties.
508 Normally, privileged users inside a jail are treated as unprivileged by
510 When this parameter is set, such users are treated as privileged, and
511 may manipulate system file flags subject to the usual constraints on
512 .Va kern.securelevel .
514 privileged users inside the jail will be able to mount and unmount file
515 system types marked as jail-friendly.
518 command can be used to find file system types available for mount from
520 This permission is effective only if
522 is set to a value lower than 2.
523 .It Va allow.mount.devfs
524 privileged users inside the jail will be able to mount and unmount the
526 This permission is effective only together with
530 is set to a value lower than 2.
531 The devfs ruleset should be restricted from the default by using the
534 .It Va allow.mount.nullfs
535 privileged users inside the jail will be able to mount and unmount the
537 This permission is effective only together with
541 is set to a value lower than 2.
542 .It Va allow.mount.procfs
543 privileged users inside the jail will be able to mount and unmount the
545 This permission is effective only together with
549 is set to a value lower than 2.
550 .It Va allow.mount.tmpfs
551 privileged users inside the jail will be able to mount and unmount the
553 This permission is effective only together with
557 is set to a value lower than 2.
558 .It Va allow.mount.zfs
559 privileged users inside the jail will be able to mount and unmount the
561 This permission is effective only together with
565 is set to a value lower than 2.
568 for information on how to configure the ZFS filesystem to operate from
571 The jail root may administer quotas on the jail's filesystem(s).
572 This includes filesystems that the jail may share with other jails or
573 with non-jailed parts of the system.
574 .It Va allow.socket_af
575 Sockets within a jail are normally restricted to IPv4, IPv6, local
576 (UNIX), and route. This allows access to other protocol stacks that
577 have not had jail functionality added to them.
581 There are pseudo-parameters that are not passed to the kernel, but are
584 to set up the jail environment, often by running specified commands
585 when jails are created or removed.
588 command parameters are
590 command lines that are run in either the system or jail environment.
591 They may be given multiple values, which run would the specified
592 commands in sequence.
593 All commands must succeed (return a zero exit status), or the jail will
594 not be created or removed, as appropriate.
596 The pseudo-parameters are:
597 .Bl -tag -width indent
599 Command(s) to run in the system environment before a jail is created.
601 Command(s) to run in the jail environment when a jail is created.
602 A typical command to run is
607 for use when specifying a jail directly on the command line.
608 Unlike other parameters whose value is a single string,
610 uses the remainder of the
612 command line as its own arguments.
613 .It Va exec.poststart
614 Command(s) to run in the system environment after a jail is created,
617 commands have completed.
619 Command(s) to run in the system environment before a jail is removed.
621 Command(s) to run in the jail environment before a jail is removed,
624 commands have completed.
625 A typical command to run is
626 .Dq sh /etc/rc.shutdown .
628 Command(s) to run in the system environment after a jail is removed.
630 Run commands in a clean environment.
631 The environment is discarded except for
632 .Ev HOME , SHELL , TERM
638 are set to the target login's default values.
640 is set to the target login.
642 is imported from the current environment.
643 The environment variables from the login class capability database for the
644 target login are also set.
645 .It Va exec.jail_user
646 The user to run commands as, when running in the jail environment.
647 The default is to run the commands as the current user.
648 .It Va exec.system_jail_user
649 This boolean option looks for the
653 file, instead of in the jail's file.
654 .It Va exec.system_user
655 The user to run commands as, when running in the system environment.
656 The default is to run the commands as the current user.
658 The maximum amount of time to wait for a command to complete, in
660 If a command is still running after this timeout has passed,
661 the jail will not be created or removed, as appropriate.
662 .It Va exec.consolelog
663 A file to direct command output (stdout and stderr) to.
665 The FIB (routing table) to set when running commands inside the jail.
667 The maximum amount of time to wait for a jail's processes to exit
670 signal (which happens after the
672 commands have completed).
673 After this many seconds have passed, the jail will be removed, which
674 will kill any remaining processes.
675 If this is set to zero, no
677 is sent and the jail is immediately removed.
678 The default is 10 seconds.
680 A network interface to add the jail's IP addresses
685 An alias for each address will be added to the interface before the
686 jail is created, and will be removed from the interface after the
689 In addition to the IP addresses that are passed to the kernel, an
690 interface and/or a netmask may also be specified, in the form
691 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask .
692 If an interface is given before the IP address, an alias for the address
693 will be added to that interface, as it is with the
696 If a netmask in either dotted-quad or CIDR form is given
697 after an IP address, it will be used when adding the IP alias.
699 In addition to the IP addresses that are passed to the kernel,
700 an interface and/or a prefix may also be specified, in the form
701 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix .
702 .It Va vnet.interface
703 A network interface to give to a vnet-enabled jail after is it created.
704 The interface will automatically be released when the jail is removed.
708 parameter and add all IP addresses returned by the resolver
709 to the list of addresses
714 This may affect default address selection for outgoing IPv4 connections
716 The address first returned by the resolver for each address family
717 will be used as the primary address.
719 A filesystem to mount before creating the jail (and to unmount after
720 removing it), given as a single
726 format file containing filesystems to mount before creating a jail.
730 filesystem on the chrooted
732 directory, and apply the ruleset in the
734 parameter (or a default of ruleset 4: devfsrules_jail)
735 to restrict the devices visible inside the jail.
739 filesystem on the chrooted
743 Allow making changes to a
747 Specify a jail (or jails) that this jail depends on.
748 Any such jails must be fully created, up to the last
750 command, before any action will taken to create this jail.
751 When jails are removed the opposite is true:
752 this jail must be fully removed, up to the last
754 command, before the jail(s) it depends on are stopped.
757 Jails are typically set up using one of two philosophies: either to
758 constrain a specific application (possibly running with privilege), or
760 .Dq "virtual system image"
761 running a variety of daemons and services.
762 In both cases, a fairly complete file system install of
765 required, so as to provide the necessary command line tools, daemons,
766 libraries, application configuration files, etc.
767 However, for a virtual server configuration, a fair amount of
768 additional work is required so as to replace the
771 This manual page documents the configuration steps necessary to support
772 either of these steps, although the configuration steps may need to be
773 refined based on local requirements.
774 .Ss "Setting up a Jail Directory Tree"
775 To set up a jail directory tree containing an entire
777 distribution, the following
779 command script can be used:
784 make world DESTDIR=$D
785 make distribution DESTDIR=$D
788 In many cases this example would put far more in the jail than needed.
789 In the other extreme case a jail might contain only one file:
790 the executable to be run in the jail.
792 We recommend experimentation, and caution that it is a lot easier to
795 jail and remove things until it stops working,
796 than it is to start with a
798 jail and add things until it works.
799 .Ss "Setting Up a Jail"
800 Do what was described in
801 .Sx "Setting Up a Jail Directory Tree"
802 to build the jail directory tree.
803 For the sake of this example, we will
804 assume you built it in
805 .Pa /data/jail/testjail ,
808 Substitute below as needed with your
809 own directory, IP address, and hostname.
810 .Ss "Setting up the Host Environment"
811 First, set up the real system's environment to be
813 For consistency, we will refer to the parent box as the
814 .Dq "host environment" ,
815 and to the jailed virtual machine as the
816 .Dq "jail environment" .
817 Since jails are implemented using IP aliases, one of the first things to do
818 is to disable IP services on the host system that listen on all local
819 IP addresses for a service.
820 If a network service is present in the host environment that binds all
821 available IP addresses rather than specific IP addresses, it may service
822 requests sent to jail IP addresses if the jail did not bind the port.
825 to only listen on the
826 appropriate IP address, and so forth.
829 in the host environment:
830 .Bd -literal -offset indent
832 inetd_flags="-wW -a 192.0.2.23"
837 is the native IP address for the host system, in this example.
838 Daemons that run out of
840 can be easily configured to use only the specified host IP address.
842 will need to be manually configured \(em for some this is possible through
844 flags entries; for others it is necessary to modify per-application
845 configuration files, or to recompile the application.
846 The following frequently deployed services must have their individual
847 configuration files modified to limit the application to listening
848 to a specific IP address:
852 it is necessary to modify
853 .Pa /etc/ssh/sshd_config .
857 it is necessary to modify
858 .Pa /etc/mail/sendmail.cf .
862 it is necessary to modify
863 .Pa /etc/namedb/named.conf .
865 In addition, a number of services must be recompiled in order to run
866 them in the host environment.
867 This includes most applications providing services using
874 In general, applications for which it is not possible to specify which
875 IP address to bind should not be run in the host environment unless they
876 should also service requests sent to jail IP addresses.
878 NFS from the host environment may also cause confusion, and cannot be
879 easily reconfigured to use only specific IPs, as some NFS services are
880 hosted directly from the kernel.
881 Any third-party network software running
882 in the host environment should also be checked and configured so that it
883 does not bind all IP addresses, which would result in those services also
884 appearing to be offered by the jail environments.
887 these daemons have been disabled or fixed in the host environment, it is
888 best to reboot so that all daemons are in a known state, to reduce the
889 potential for confusion later (such as finding that when you send mail
890 to a jail, and its sendmail is down, the mail is delivered to the host,
892 .Ss "Configuring the Jail"
893 Start any jail for the first time without configuring the network
894 interface so that you can clean it up a little and set up accounts.
896 with any machine (virtual or not), you will need to set a root password, time
898 Some of these steps apply only if you intend to run a full virtual server
899 inside the jail; others apply both for constraining a particular application
900 or for running a virtual server.
902 Start a shell in the jail:
903 .Bd -literal -offset indent
904 jail -c path=/data/jail/testjail mount.devfs \\
905 host.hostname=testhostname ip4.addr=192.0.2.100 \\
909 Assuming no errors, you will end up with a shell prompt within the jail.
911 .Pa /usr/sbin/sysinstall
912 and do the post-install configuration to set various configuration options,
913 or perform these actions manually by editing
917 .Bl -bullet -offset indent -compact
921 so that name resolution within the jail will work correctly.
929 Set a root password, probably different from the real host system.
933 Add accounts for users in the jail environment.
935 Install any packages the environment requires.
938 You may also want to perform any package-specific configuration (web servers,
939 SSH servers, etc), patch up
941 so it logs as you would like, etc.
942 If you are not using a virtual server, you may wish to modify
944 in the host environment to listen on the syslog socket in the jail
945 environment; in this example, the syslog socket would be stored in
946 .Pa /data/jail/testjail/var/run/log .
948 Exit from the shell, and the jail will be shut down.
949 .Ss "Starting the Jail"
950 You are now ready to restart the jail and bring up the environment with
951 all of its daemons and other programs.
952 Create an entry for the jail in
954 .Bd -literal -offset indent
956 path = /tmp/jail/testjail;
958 host.hostname = testhostname;
959 ip4.addr = 192.0.2.100;
961 exec.start = "/bin/sh /etc/rc";
962 exec.stop = "/bin/sh /etc/rc.shutdown";
966 To start a virtual server environment,
968 is run to launch various daemons and services, and
970 is run to shut them down when the jail is removed.
971 If you are running a single application in the jail,
972 substitute the command used to start the application for
973 .Dq /bin/sh /etc/rc ;
974 there may be some script available to cleanly shut down the application,
975 or it may be sufficient to go without a stop command, and have
981 Start the jail by running:
982 .Bd -literal -offset indent
986 A few warnings may be produced; however, it should all work properly.
987 You should be able to see
990 and other processes running within the jail using
994 flag appearing beside jailed processes.
995 To see an active list of jails, use
999 is enabled in the jail environment, you should be able to
1001 to the hostname or IP address of the jailed environment, and log
1002 in using the accounts you created previously.
1004 It is possible to have jails started at boot time.
1009 for more information.
1010 .Ss "Managing the Jail"
1011 Normal machine shutdown commands, such as
1016 cannot be used successfully within the jail.
1017 To kill all processes from within a jail, you may use one of the
1018 following commands, depending on what you want to accomplish:
1019 .Bd -literal -offset indent
1028 signals to all processes in the jail \(em be careful not to run this from
1029 the host environment!
1030 Once all of the jail's processes have died, unless the jail was created
1033 parameter, the jail will be removed.
1035 the intended use of the jail, you may also want to run
1036 .Pa /etc/rc.shutdown
1037 from within the jail.
1039 To shut down the jail from the outside, simply remove it with
1042 which will run any commands specified by
1048 to any remaining jailed processes.
1051 .Pa /proc/ Ns Ar pid Ns Pa /status
1052 file contains, as its last field, the name of the jail in which the
1055 to indicate that the process is not running within a jail.
1058 command also shows a
1060 flag for processes in a jail.
1062 You can also list/kill processes based on their jail ID.
1063 To show processes and their jail ID, use the following command:
1065 .Dl "ps ax -o pid,jid,args"
1067 To show and then kill processes in jail number 3 use the following commands:
1068 .Bd -literal -offset indent
1075 .Ss "Jails and File Systems"
1076 It is not possible to
1080 any file system inside a jail unless the file system is marked
1081 jail-friendly, the jail's
1083 parameter is set, and the jail's
1085 parameter is lower than 2.
1087 Multiple jails sharing the same file system can influence each other.
1088 For example, a user in one jail can fill the file system,
1089 leaving no space for processes in the other jail.
1092 to prevent this will not work either, as the file system quotas
1093 are not aware of jails but only look at the user and group IDs.
1094 This means the same user ID in two jails share a single file
1096 One would need to use one file system per jail to make this work.
1097 .Ss "Sysctl MIB Entries"
1099 .Va security.jail.jailed
1100 can be used to determine if a process is running inside a jail (value
1101 is one) or not (value is zero).
1104 .Va security.jail.max_af_ips
1105 determines how may address per address family a jail may have.
1108 Some MIB variables have per-jail settings.
1109 Changes to these variables by a jailed process do not affect the host
1110 environment, only the jail environment.
1112 .Va kern.securelevel ,
1114 .Va kern.domainname ,
1118 .Ss "Hierarchical Jails"
1121 parameter, processes within a jail may be able to create jails of their own.
1122 These child jails are kept in a hierarchy, with jails only able to see and/or
1123 modify the jails they created (or those jails' children).
1124 Each jail has a read-only
1126 parameter, containing the
1128 of the jail that created it; a
1130 of 0 indicates the jail is a child of the current jail (or is a top-level
1131 jail if the current process isn't jailed).
1133 Jailed processes are not allowed to confer greater permissions than they
1134 themselves are given, e.g., if a jail is created with
1136 it is not able to create a jail with
1139 Similarly, such restrictions as
1143 may not be bypassed in child jails.
1145 A child jail may in turn create its own child jails if its own
1147 parameter is set (remember it is zero by default).
1148 These jails are visible to and can be modified by their parent and all
1151 Jail names reflect this hierarchy, with a full name being an MIB-type string
1153 For example, if a base system process creates a jail
1155 and a process under that jail creates another jail
1157 then the second jail will be seen as
1159 in the base system (though it is only seen as
1161 to any processes inside jail
1163 Jids on the other hand exist in a single space, and each jail must have a
1166 Like the names, a child jail's
1168 appears relative to its creator's own
1170 This is by virtue of the child jail being created in the chrooted
1171 environment of the first jail.
1207 Hierarchical/extensible jails were introduced in
1209 The configuration file was introduced in
1213 The jail feature was written by
1214 .An Poul-Henning Kamp
1216 .Pa http://www.rndassociates.com/
1217 who contributed it to
1221 wrote the extended documentation, found a few bugs, added
1222 a few new features, and cleaned up the userland jail environment.
1225 added multi-IP jail support for IPv4 and IPv6 based on a patch
1227 .An Pawel Jakub Dawidek
1231 added the extensible jail parameters, hierarchical jails,
1232 and the configuration file.
1234 It might be a good idea to add an
1235 address alias flag such that daemons listening on all IPs
1237 will not bind on that address, which would facilitate building a safe
1238 host environment such that host daemons do not impose on services offered
1240 Currently, the simplest answer is to minimize services
1241 offered on the host, possibly limiting it to services offered from
1243 which is easily configurable.
1245 Great care should be taken when managing directories visible within the jail.
1246 For example, if a jailed process has its current working directory set to a
1247 directory that is moved out of the jail's chroot, then the process may gain
1248 access to the file space outside of the jail.
1249 It is recommended that directories always be copied, rather than moved, out
1252 In addition, there are several ways in which an unprivileged user
1253 outside the jail can cooperate with a privileged user inside the jail
1254 and thereby obtain elevated privileges in the host environment.
1255 Most of these attacks can be mitigated by ensuring that the jail root
1256 is not accessible to unprivileged users in the host environment.
1257 Regardless, as a general rule, untrusted users with privileged access
1258 to a jail should not be given access to the host environment.
projects / FreeBSD / FreeBSD.git / blob