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2 .\" Copyright (c) 2008-2012 James Gritton
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33 .Nd "manage system jails"
41 .Ar param Ns = Ns Ar value ...
42 .Op Cm command Ns = Ns Ar command ...
53 .Op Cm * | Ar jail ...
60 .Op Fl s Ar securelevel
61 .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, netmask and additional paramters (as supported by
692 may also be specified, in the form
693 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
694 If an interface is given before the IP address, an alias for the address
695 will be added to that interface, as it is with the
698 If a netmask in either dotted-quad or CIDR form is given
699 after an IP address, it will be used when adding the IP alias.
700 If additional parameters are specified then they will also be used when
703 In addition to the IP addresses that are passed to the kernel,
704 an interface, prefix and additional parameters (as supported by
706 may also be specified, in the form
707 .Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
708 .It Va vnet.interface
709 A network interface to give to a vnet-enabled jail after is it created.
710 The interface will automatically be released when the jail is removed.
714 parameter and add all IP addresses returned by the resolver
715 to the list of addresses
720 This may affect default address selection for outgoing IPv4 connections
722 The address first returned by the resolver for each address family
723 will be used as the primary address.
725 A filesystem to mount before creating the jail (and to unmount after
726 removing it), given as a single
732 format file containing filesystems to mount before creating a jail.
736 filesystem on the chrooted
738 directory, and apply the ruleset in the
740 parameter (or a default of ruleset 4: devfsrules_jail)
741 to restrict the devices visible inside the jail.
745 filesystem on the chrooted
749 Allow making changes to a
753 Specify a jail (or jails) that this jail depends on.
754 Any such jails must be fully created, up to the last
756 command, before any action will taken to create this jail.
757 When jails are removed the opposite is true:
758 this jail must be fully removed, up to the last
760 command, before the jail(s) it depends on are stopped.
763 Jails are typically set up using one of two philosophies: either to
764 constrain a specific application (possibly running with privilege), or
766 .Dq "virtual system image"
767 running a variety of daemons and services.
768 In both cases, a fairly complete file system install of
771 required, so as to provide the necessary command line tools, daemons,
772 libraries, application configuration files, etc.
773 However, for a virtual server configuration, a fair amount of
774 additional work is required so as to replace the
777 This manual page documents the configuration steps necessary to support
778 either of these steps, although the configuration steps may need to be
779 refined based on local requirements.
780 .Ss "Setting up a Jail Directory Tree"
781 To set up a jail directory tree containing an entire
783 distribution, the following
785 command script can be used:
790 make world DESTDIR=$D
791 make distribution DESTDIR=$D
794 In many cases this example would put far more in the jail than needed.
795 In the other extreme case a jail might contain only one file:
796 the executable to be run in the jail.
798 We recommend experimentation, and caution that it is a lot easier to
801 jail and remove things until it stops working,
802 than it is to start with a
804 jail and add things until it works.
805 .Ss "Setting Up a Jail"
806 Do what was described in
807 .Sx "Setting Up a Jail Directory Tree"
808 to build the jail directory tree.
809 For the sake of this example, we will
810 assume you built it in
811 .Pa /data/jail/testjail ,
814 Substitute below as needed with your
815 own directory, IP address, and hostname.
816 .Ss "Setting up the Host Environment"
817 First, set up the real system's environment to be
819 For consistency, we will refer to the parent box as the
820 .Dq "host environment" ,
821 and to the jailed virtual machine as the
822 .Dq "jail environment" .
823 Since jails are implemented using IP aliases, one of the first things to do
824 is to disable IP services on the host system that listen on all local
825 IP addresses for a service.
826 If a network service is present in the host environment that binds all
827 available IP addresses rather than specific IP addresses, it may service
828 requests sent to jail IP addresses if the jail did not bind the port.
831 to only listen on the
832 appropriate IP address, and so forth.
835 in the host environment:
836 .Bd -literal -offset indent
838 inetd_flags="-wW -a 192.0.2.23"
843 is the native IP address for the host system, in this example.
844 Daemons that run out of
846 can be easily configured to use only the specified host IP address.
848 will need to be manually configured \(em for some this is possible through
850 flags entries; for others it is necessary to modify per-application
851 configuration files, or to recompile the application.
852 The following frequently deployed services must have their individual
853 configuration files modified to limit the application to listening
854 to a specific IP address:
858 it is necessary to modify
859 .Pa /etc/ssh/sshd_config .
863 it is necessary to modify
864 .Pa /etc/mail/sendmail.cf .
868 it is necessary to modify
869 .Pa /etc/namedb/named.conf .
871 In addition, a number of services must be recompiled in order to run
872 them in the host environment.
873 This includes most applications providing services using
880 In general, applications for which it is not possible to specify which
881 IP address to bind should not be run in the host environment unless they
882 should also service requests sent to jail IP addresses.
884 NFS from the host environment may also cause confusion, and cannot be
885 easily reconfigured to use only specific IPs, as some NFS services are
886 hosted directly from the kernel.
887 Any third-party network software running
888 in the host environment should also be checked and configured so that it
889 does not bind all IP addresses, which would result in those services also
890 appearing to be offered by the jail environments.
893 these daemons have been disabled or fixed in the host environment, it is
894 best to reboot so that all daemons are in a known state, to reduce the
895 potential for confusion later (such as finding that when you send mail
896 to a jail, and its sendmail is down, the mail is delivered to the host,
898 .Ss "Configuring the Jail"
899 Start any jail for the first time without configuring the network
900 interface so that you can clean it up a little and set up accounts.
902 with any machine (virtual or not), you will need to set a root password, time
904 Some of these steps apply only if you intend to run a full virtual server
905 inside the jail; others apply both for constraining a particular application
906 or for running a virtual server.
908 Start a shell in the jail:
909 .Bd -literal -offset indent
910 jail -c path=/data/jail/testjail mount.devfs host.hostname=testhostname \\
911 ip4.addr=192.0.2.100 command=/bin/sh
914 Assuming no errors, you will end up with a shell prompt within the jail.
916 .Pa /usr/sbin/sysinstall
917 and do the post-install configuration to set various configuration options,
918 or perform these actions manually by editing
922 .Bl -bullet -offset indent -compact
926 so that name resolution within the jail will work correctly.
934 Set a root password, probably different from the real host system.
938 Add accounts for users in the jail environment.
940 Install any packages the environment requires.
943 You may also want to perform any package-specific configuration (web servers,
944 SSH servers, etc), patch up
946 so it logs as you would like, etc.
947 If you are not using a virtual server, you may wish to modify
949 in the host environment to listen on the syslog socket in the jail
950 environment; in this example, the syslog socket would be stored in
951 .Pa /data/jail/testjail/var/run/log .
953 Exit from the shell, and the jail will be shut down.
954 .Ss "Starting the Jail"
955 You are now ready to restart the jail and bring up the environment with
956 all of its daemons and other programs.
957 Create an entry for the jail in
959 .Bd -literal -offset indent
961 path = /tmp/jail/testjail;
963 host.hostname = testhostname;
964 ip4.addr = 192.0.2.100;
966 exec.start = "/bin/sh /etc/rc";
967 exec.stop = "/bin/sh /etc/rc.shutdown";
971 To start a virtual server environment,
973 is run to launch various daemons and services, and
975 is run to shut them down when the jail is removed.
976 If you are running a single application in the jail,
977 substitute the command used to start the application for
978 .Dq /bin/sh /etc/rc ;
979 there may be some script available to cleanly shut down the application,
980 or it may be sufficient to go without a stop command, and have
986 Start the jail by running:
987 .Bd -literal -offset indent
991 A few warnings may be produced; however, it should all work properly.
992 You should be able to see
995 and other processes running within the jail using
999 flag appearing beside jailed processes.
1000 To see an active list of jails, use
1004 is enabled in the jail environment, you should be able to
1006 to the hostname or IP address of the jailed environment, and log
1007 in using the accounts you created previously.
1009 It is possible to have jails started at boot time.
1014 for more information.
1015 .Ss "Managing the Jail"
1016 Normal machine shutdown commands, such as
1021 cannot be used successfully within the jail.
1022 To kill all processes from within a jail, you may use one of the
1023 following commands, depending on what you want to accomplish:
1024 .Bd -literal -offset indent
1033 signals to all processes in the jail \(em be careful not to run this from
1034 the host environment!
1035 Once all of the jail's processes have died, unless the jail was created
1038 parameter, the jail will be removed.
1040 the intended use of the jail, you may also want to run
1041 .Pa /etc/rc.shutdown
1042 from within the jail.
1044 To shut down the jail from the outside, simply remove it with
1047 which will run any commands specified by
1053 to any remaining jailed processes.
1056 .Pa /proc/ Ns Ar pid Ns Pa /status
1057 file contains, as its last field, the name of the jail in which the
1060 to indicate that the process is not running within a jail.
1063 command also shows a
1065 flag for processes in a jail.
1067 You can also list/kill processes based on their jail ID.
1068 To show processes and their jail ID, use the following command:
1070 .Dl "ps ax -o pid,jid,args"
1072 To show and then kill processes in jail number 3 use the following commands:
1073 .Bd -literal -offset indent
1080 .Ss "Jails and File Systems"
1081 It is not possible to
1085 any file system inside a jail unless the file system is marked
1086 jail-friendly, the jail's
1088 parameter is set, and the jail's
1090 parameter is lower than 2.
1092 Multiple jails sharing the same file system can influence each other.
1093 For example, a user in one jail can fill the file system,
1094 leaving no space for processes in the other jail.
1097 to prevent this will not work either, as the file system quotas
1098 are not aware of jails but only look at the user and group IDs.
1099 This means the same user ID in two jails share a single file
1101 One would need to use one file system per jail to make this work.
1102 .Ss "Sysctl MIB Entries"
1104 .Va security.jail.jailed
1105 can be used to determine if a process is running inside a jail (value
1106 is one) or not (value is zero).
1109 .Va security.jail.max_af_ips
1110 determines how may address per address family a jail may have.
1113 Some MIB variables have per-jail settings.
1114 Changes to these variables by a jailed process do not affect the host
1115 environment, only the jail environment.
1117 .Va kern.securelevel ,
1119 .Va kern.domainname ,
1123 .Ss "Hierarchical Jails"
1126 parameter, processes within a jail may be able to create jails of their own.
1127 These child jails are kept in a hierarchy, with jails only able to see and/or
1128 modify the jails they created (or those jails' children).
1129 Each jail has a read-only
1131 parameter, containing the
1133 of the jail that created it; a
1135 of 0 indicates the jail is a child of the current jail (or is a top-level
1136 jail if the current process isn't jailed).
1138 Jailed processes are not allowed to confer greater permissions than they
1139 themselves are given, e.g., if a jail is created with
1141 it is not able to create a jail with
1144 Similarly, such restrictions as
1148 may not be bypassed in child jails.
1150 A child jail may in turn create its own child jails if its own
1152 parameter is set (remember it is zero by default).
1153 These jails are visible to and can be modified by their parent and all
1156 Jail names reflect this hierarchy, with a full name being an MIB-type string
1158 For example, if a base system process creates a jail
1160 and a process under that jail creates another jail
1162 then the second jail will be seen as
1164 in the base system (though it is only seen as
1166 to any processes inside jail
1168 Jids on the other hand exist in a single space, and each jail must have a
1171 Like the names, a child jail's
1173 appears relative to its creator's own
1175 This is by virtue of the child jail being created in the chrooted
1176 environment of the first jail.
1213 Hierarchical/extensible jails were introduced in
1215 The configuration file was introduced in
1219 The jail feature was written by
1220 .An Poul-Henning Kamp
1222 .Pa http://www.rndassociates.com/
1223 who contributed it to
1227 wrote the extended documentation, found a few bugs, added
1228 a few new features, and cleaned up the userland jail environment.
1231 added multi-IP jail support for IPv4 and IPv6 based on a patch
1233 .An Pawel Jakub Dawidek
1237 added the extensible jail parameters, hierarchical jails,
1238 and the configuration file.
1240 It might be a good idea to add an
1241 address alias flag such that daemons listening on all IPs
1243 will not bind on that address, which would facilitate building a safe
1244 host environment such that host daemons do not impose on services offered
1246 Currently, the simplest answer is to minimize services
1247 offered on the host, possibly limiting it to services offered from
1249 which is easily configurable.
1251 Great care should be taken when managing directories visible within the jail.
1252 For example, if a jailed process has its current working directory set to a
1253 directory that is moved out of the jail's chroot, then the process may gain
1254 access to the file space outside of the jail.
1255 It is recommended that directories always be copied, rather than moved, out
1258 In addition, there are several ways in which an unprivileged user
1259 outside the jail can cooperate with a privileged user inside the jail
1260 and thereby obtain elevated privileges in the host environment.
1261 Most of these attacks can be mitigated by ensuring that the jail root
1262 is not accessible to unprivileged users in the host environment.
1263 Regardless, as a general rule, untrusted users with privileged access
1264 to a jail should not be given access to the host environment.
projects / FreeBSD / releng / 10.1.git / blob