1.\" 2.\" Copyright (c) 2000 Robert N. M. Watson 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 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. 13.\" 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 24.\" SUCH DAMAGE. 25.\" 26.\" 27.\" ---------------------------------------------------------------------------- 28.\" "THE BEER-WARE LICENSE" (Revision 42): 29.\" <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you 30.\" can do whatever you want with this stuff. If we meet some day, and you think 31.\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp 32.\" ---------------------------------------------------------------------------- 33.\" 34.\" $FreeBSD: src/usr.sbin/jail/jail.8,v 1.13.2.15 2003/05/08 13:04:24 maxim Exp $ 35.\" $DragonFly: src/usr.sbin/jail/jail.8,v 1.11 2008/05/02 02:05:07 swildner Exp $ 36.\" 37.Dd August 6, 2009 38.Dt JAIL 8 39.Os 40.Sh NAME 41.Nm jail 42.Nd "imprison process and its descendants" 43.Sh SYNOPSIS 44.Nm 45.Op Fl i 46.Op Fl l u Ar username | Fl U Ar username 47.Ar path hostname ip-list command ... 48.Sh DESCRIPTION 49The 50.Nm 51command imprisons a process and all future descendants. 52.Pp 53The options are as follows: 54.Bl -tag -width ".Fl u Ar username" 55.It Fl i 56Output the jail identifier of the newly created jail. 57.It Fl l 58Run program in the clean environment. 59The environment is discarded except for 60.Ev HOME , SHELL , TERM 61and 62.Ev USER . 63.Ev HOME 64and 65.Ev SHELL 66are set to the target login's default values. 67.Ev USER 68is set to the target login. 69.Ev TERM 70is imported from the current environment. 71The environment variables from the login class capability database for the 72target login are also set. 73.It Fl u Ar username 74The user name as whom the 75.Ar command 76should run. 77.It Fl U Ar username 78The user name from jailed environment as whom the 79.Ar command 80should run. 81.It Ar path 82Directory which is to be the root of the prison. 83.It Ar hostname 84Hostname of the prison. 85.It Ar ip-list 86Comma separated IP list assigned to the prison. 87.It Ar command 88Pathname of the program which is to be executed. 89.El 90.Pp 91Please see the 92.Xr jail 2 93man page for further details. 94.Sh EXAMPLES 95.Ss "Setting up a Jail Directory Tree" 96This example shows how to setup a jail directory tree 97containing an entire 98.Dx 99distribution, provided that you built world before already: 100.Bd -literal 101D=/here/is/the/jail 102cd /usr/src 103mkdir -p $D 104make installworld DESTDIR=$D 105cd etc 106make distribution DESTDIR=$D 107cd $D 108ln -sf dev/null boot/kernel 109.Ed 110.Pp 111In many cases this example would put far more stuff in the jail than is needed. 112In the other extreme case a jail might contain only one single file: 113the executable to be run in the jail. 114.Pp 115We recommend experimentation and caution that it is a lot easier to 116start with a 117.Dq fat 118jail and remove things until it stops working, 119than it is to start with a 120.Dq thin 121jail and add things until it works. 122.Ss "Setting Up a Jail" 123Do what was described in 124.Sx "Setting Up a Jail Directory Tree" 125to build the jail directory tree. 126For the sake of this example, we will 127assume you built it in 128.Pa /data/jail/192.168.11.100 , 129named for the external jail IP address. 130Substitute below as needed with your 131own directory, IP addresses, and hostname. 132.Pp 133First, you will want to set up your real system's environment to be 134.Dq jail-friendly . 135For consistency, we will refer to the parent box as the 136.Dq "host environment" , 137and to the jailed virtual machine as the 138.Dq "jail environment" . 139Because jail is implemented using IP aliases, one of the first things to do 140is to disable IP services on the host system that listen on all local 141IP addresses for a service. 142This means changing 143.Xr inetd 8 144to only listen on the 145appropriate IP address, and so forth. 146Add the following to 147.Pa /etc/rc.conf 148in the host environment: 149.Bd -literal -offset indent 150sendmail_enable="NO" 151inetd_flags="-wW -a 192.168.11.23" 152rpcbind_enable="NO" 153.Ed 154.Pp 155.Li 192.168.11.23 156is the native IP address for the host system, in this example. 157Daemons that run out of 158.Xr inetd 8 159can be easily set to use only the specified host IP address. 160Other daemons 161will need to be manually configured\(emfor some this is possible through 162the 163.Xr rc.conf 5 164flags entries, for others it is not possible without munging 165the per-application configuration files, or even recompiling. 166For those 167applications that cannot specify the IP they run on, it is better to disable 168them, if possible. 169.Pp 170A number of daemons ship with the base system that may have problems when 171run from outside of a jail in a jail-centric environment. 172This includes 173.Xr sendmail 8 , 174.Xr named 8 , 175and 176.Xr rpcbind 8 . 177While 178.Xr sendmail 8 179and 180.Xr named 8 181can be configured to listen only on a specific 182IP using their configuration files, in most cases it is easier to simply 183run the daemons in jails only, and not in the host environment. 184Attempting to serve 185NFS from the host environment may also cause confusion, and cannot be 186easily reconfigured to use only specific IPs, as some NFS services are 187hosted directly from the kernel. 188Any third party network software running 189in the host environment should also be checked and configured so that it 190does not bind all IP addresses, which would result in those services also 191appearing to be offered by the jail environments. 192.Pp 193Once 194these daemons have been disabled or fixed in the host environment, it is 195best to reboot so that all daemons are in a known state, to reduce the 196potential for confusion later (such as finding that when you send mail 197to a jail, and its sendmail is down, the mail is delivered to the host, 198etc.) 199.Pp 200Start any jails for the first time without configuring the network 201interface so that you can clean it up a little and set up accounts. 202As 203with any machine (virtual or not) you will need to set a root password, time 204zone, etc. 205.Pp 206Now start the jail: 207.Pp 208.Dl "jail /data/jail/192.168.11.100 testhostname 127.0.0.1,192.168.11.100 /bin/sh" 209.Pp 210You will end up with a shell prompt, assuming no errors, within the jail. 211You can now do the post-install configuration to set various configuration 212options by editing 213.Pa /etc/rc.conf , 214etc. 215.Pp 216.Bl -bullet -offset indent -compact 217.It 218Disable the port mapper 219.Pa ( /etc/rc.conf : 220.Li rpcbind_enable="NO" ) 221.It 222Run 223.Xr newaliases 1 224to quell 225.Xr sendmail 8 226warnings. 227.It 228Disable interface configuration to quell startup warnings about 229.Xr ifconfig 8 230.Pq Li network_interfaces="" 231.It 232Configure 233.Pa /etc/resolv.conf 234so that name resolution within the jail will work correctly 235.It 236Set a root password, probably different from the real host system 237.It 238Set the timezone with 239.Xr tzsetup 8 240.It 241Add accounts for users in the jail environment 242.It 243Install any packages that you think the environment requires 244.El 245.Pp 246You may also want to perform any package-specific configuration (web servers, 247SSH servers, etc), patch up 248.Pa /etc/syslog.conf 249so it logs as you would like, etc. 250.Pp 251Exit from the shell, and the jail will be shut down. 252.Ss "Starting the Jail" 253You are now ready to restart the jail and bring up the environment with 254all of its daemons and other programs. 255To do this, first bring up the 256virtual host interface, and then start the jail's 257.Pa /etc/rc 258script from within the jail. 259.Pp 260NOTE: If you plan to allow untrusted users to have root access inside the 261jail, you may wish to consider setting the 262.Va jail.set_hostname_allowed 263to 0. 264Please see the management reasons why this is a good idea. 265If you do decide to set this variable, 266it must be set before starting any jails, and once each boot. 267.Bd -literal -offset indent 268ifconfig ed0 inet alias 192.168.11.100/32 269mount -t procfs proc /data/jail/192.168.11.100/proc 270jail /data/jail/192.168.11.100 testhostname 127.0.0.1,192.168.11.100 \\ 271 /bin/sh /etc/rc 272.Ed 273.Pp 274A few warnings will be produced, because most 275.Xr sysctl 8 276configuration variables cannot be set from within the jail, as they are 277global across all jails and the host environment. 278However, it should all 279work properly. 280You should be able to see 281.Xr inetd 8 , 282.Xr syslogd 8 , 283and other processes running within the jail using 284.Xr ps 1 , 285with the 286.Ql J 287flag appearing beside jailed processes. 288You should also be able to 289.Xr telnet 1 290to the hostname or IP address of the jailed environment, and log 291in using the accounts you created previously. 292.Ss "Managing the Jail" 293Normal machine shutdown commands, such as 294.Xr halt 8 , 295.Xr reboot 8 , 296and 297.Xr shutdown 8 , 298cannot be used successfully within the jail. 299To kill all processes in a 300jail, you may log into the jail and, as root, use one of the following 301commands, depending on what you want to accomplish: 302.Bd -literal -offset indent 303kill -TERM -1 304kill -KILL -1 305.Ed 306.Pp 307This will send the 308.Dv SIGTERM 309or 310.Dv SIGKILL 311signals to all processes in the jail from within the jail. 312Depending on 313the intended use of the jail, you may also want to run 314.Pa /etc/rc.shutdown 315from within the jail. 316Currently there is no way to insert new processes 317into a jail, so you must first log into the jail before performing these 318actions. 319.Pp 320To kill processes from outside the jail, you must individually identify the 321PID of each process to be killed. 322The 323.Pa /proc/ Ns Ar pid Ns Pa /status 324file contains, as its last field, the hostname of the jail in which the 325process runs, or 326.Dq Li - 327to indicate that the process is not running within a jail. 328The 329.Xr ps 1 330command also shows a 331.Ql J 332flag for processes in a jail. 333However, the hostname for a jail may be, by 334default, modified from within the jail, so the 335.Pa /proc 336status entry is unreliable by default. 337To disable the setting of the hostname 338from within a jail, set the 339.Va jail.set_hostname_allowed 340sysctl variable in the host environment to 0, which will affect all jails. 341You can have this sysctl set on each boot using 342.Xr sysctl.conf 5 . 343Just add the following line to 344.Pa /etc/sysctl.conf : 345.Pp 346.Dl jail.set_hostname_allowed=0 347.Pp 348In a future version of 349.Dx , 350the mechanisms for managing jails may be 351more refined. 352.Ss "Sysctl MIB Entries" 353Certain aspects of the jail containments environment may be modified from 354the host environment using 355.Xr sysctl 8 356MIB variables. 357Currently, these variables affect all jails on the system, although in 358the future this functionality may be finer grained. 359.Bl -tag -width XXX 360.It Va jail.set_hostname_allowed 361This MIB entry determines whether or not processes within a jail are 362allowed to change their hostname via 363.Xr hostname 1 364or 365.Xr sethostname 3 . 366In the current jail implementation, the ability to set the hostname from 367within the jail can impact management tools relying on the accuracy of jail 368information in 369.Pa /proc . 370As such, this should be disabled in environments where privileged access to 371jails is given out to untrusted parties. 372.It Va jail.socket_unixiproute_only 373The jail functionality binds IPv4 and IPv6 addresses to each jail, and limits 374access to other network addresses in the IPv4 and IPv6 space that may be available 375in the host environment. 376However, jail is not currently able to limit access to other network 377protocol stacks that have not had jail functionality added to them. 378As such, by default, processes within jails may only access protocols 379in the following domains: 380.Dv PF_LOCAL , PF_INET , PF_INET6 , 381and 382.Dv PF_ROUTE , 383permitting them access to 384.Ux 385domain sockets, 386IPv4 and IPv6 addresses, and routing sockets. 387To enable access to other domains, this MIB variable may be set to 3880. 389.It Va jail.sysvipc_allowed 390This MIB entry determines whether or not processes within a jail have access 391to System V IPC primitives. 392In the current jail implementation, System V primitives share a single 393namespace across the host and jail environments, meaning that processes 394within a jail would be able to communicate with (and potentially interfere 395with) processes outside of the jail, and in other jails. 396As such, this functionality is disabled by default, but can be enabled 397by setting this MIB entry to 1. 398.El 399.Sh SEE ALSO 400.Xr newaliases 1 , 401.Xr ps 1 , 402.Xr chroot 2 , 403.Xr jail 2 , 404.Xr procfs 5 , 405.Xr rc.conf 5 , 406.Xr sysctl.conf 5 , 407.Xr halt 8 , 408.Xr inetd 8 , 409.Xr named 8 , 410.Xr pw 8 , 411.Xr reboot 8 , 412.Xr rpcbind 8 , 413.Xr sendmail 8 , 414.Xr shutdown 8 , 415.Xr sysctl 8 , 416.Xr syslogd 8 , 417.Xr tzsetup 8 418.Sh HISTORY 419The 420.Nm 421command appeared in 422.Fx 4.0 . 423.Pp 424Support for multiple IPs and IPv6 appeared in 425.Dx 4261.7. 427.Sh AUTHORS 428.An -nosplit 429The jail feature was written by 430.An Poul-Henning Kamp 431for R&D Associates 432.Pa http://www.rndassociates.com/ 433who contributed it to 434.Fx . 435.Pp 436.An Robert Watson 437wrote the extended documentation, found a few bugs, added 438a few new features, and cleaned up the userland jail environment. 439.Pp 440.An Victor Balada Diaz 441wrote the support for multiple IPs and IPv6. Multiple IPs support 442is based on work done by 443.An Pawel Jakub Dawidek . 444.Sh BUGS 445Jail currently lacks strong management functionality, such as the ability 446to deliver signals to all processes in a jail, and to allow access to 447specific jail information via 448.Xr ps 1 449as opposed to 450.Xr procfs 5 . 451Similarly, it might be a good idea to add an 452address alias flag such that daemons listening on all IPs 453.Pq Dv INADDR_ANY 454will not bind on that address, which would facilitate building a safe 455host environment such that host daemons do not impose on services offered 456from within jails. 457Currently, the simplist answer is to minimize services 458offered on the host, possibly limiting it to services offered from 459.Xr inetd 8 460which is easily configurable. 461