883 lines
25 KiB
Groff
883 lines
25 KiB
Groff
.\"
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.\" Copyright (c) 2000, 2003 Robert N. M. Watson
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.\" Copyright (c) 2008 James Gritton
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\"
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.\" ----------------------------------------------------------------------------
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.\" "THE BEER-WARE LICENSE" (Revision 42):
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.\" <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
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.\" can do whatever you want with this stuff. If we meet some day, and you think
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.\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
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.\" ----------------------------------------------------------------------------
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.\"
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.\" $FreeBSD$
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.\"
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.Dd May 29, 2009
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.Dt JAIL 8
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.Os
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.Sh NAME
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.Nm jail
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.Nd "create or modify a system jail"
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.Sh SYNOPSIS
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.Nm
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.Op Fl dhi
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.Op Fl J Ar jid_file
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.Op Fl l u Ar username | Fl U Ar username
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.Op Fl c | m
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.Op Ar parameter=value ...
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.Br
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.Nm
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.Op Fl hi
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.Op Fl n Ar jailname
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.Op Fl J Ar jid_file
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.Op Fl s Ar securelevel
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.Op Fl l u Ar username | Fl U Ar username
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.Op Ar path hostname [ip[,..]] command ...
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.Br
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.Nm
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.Op Fl r Ar jail
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.Sh DESCRIPTION
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The
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.Nm
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utility creates a new jail or modifies an existing jail, optionally
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imprisoning the current process (and future descendants) inside it.
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.Pp
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The options are as follows:
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.Bl -tag -width indent
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.It Fl d
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Allow making changes to a
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.Va
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dying jail.
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.It Fl h
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Resolve the
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.Va host.hostname
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parameter (or
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.Va hostname )
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and add all IP addresses returned by the resolver
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to the list of
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.Va ip
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addresses for this prison.
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This may affect default address selection for outgoing IPv4 connections
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of prisons.
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The address first returned by the resolver for each address family
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will be used as primary address.
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See the
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.Va ip4.addr
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and
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.Va ip6.addr
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parameters further down for details.
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.It Fl i
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Output the jail identifier of the newly created jail.
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.It Fl n Ar jailname
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Set the jail's name.
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This is deprecated and is equivalent to setting the
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.Va name
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parameter.
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.It Fl J Ar jid_file
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Write a
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.Ar jid_file
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file, containing jail identifier, path, hostname, IP and
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command used to start the jail.
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.It Fl l
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Run program in the clean environment.
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The environment is discarded except for
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.Ev HOME , SHELL , TERM
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and
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.Ev USER .
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.Ev HOME
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and
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.Ev SHELL
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are set to the target login's default values.
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.Ev USER
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is set to the target login.
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.Ev TERM
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is imported from the current environment.
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The environment variables from the login class capability database for the
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target login are also set.
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.It Fl s Ar securelevel
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Set the
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.Va kern.securelevel
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MIB entry to the specified value inside the newly created jail.
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This is deprecated and is equivalent to setting the
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.Va securelevel
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parameter.
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.It Fl u Ar username
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The user name from host environment as whom the
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.Ar command
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should run.
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.It Fl U Ar username
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The user name from jailed environment as whom the
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.Ar command
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should run.
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.It Fl c
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Create a new jail.
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The
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.Va jid
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and
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.Va name
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parameters (if specified) must not refer to an existing jail.
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.It Fl m
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Modify an existing jail.
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One of the
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.Va jid
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or
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.Va name
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parameters must exist and refer to an existing jail.
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.It Fl cm
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Create a jail if it does not exist, or modify a jail if it does exist.
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.It Fl r
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Remove the
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.Ar jail
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specified by jid or name.
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All jailed processes are killed, and all children of this jail are also
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removed.
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.El
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.Pp
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At least one of the
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.Fl c ,
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.Fl m
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or
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.Fl r
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options must be specified.
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.Pp
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.Ar Parameters
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are listed in
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.Dq name=value
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form, following the options.
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Some parameters are boolean, and do not have a value but are set by the
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name alone with or without a
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.Dq no
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prefix, e.g.
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.Va persist
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or
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.Va nopersist .
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Any parameters not set will be given default values, often based on the
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current environment.
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.Pp
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The pseudo-parameter
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.Va command
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specifies that the current process should enter the new (or modified) jail,
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and run the specified command.
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It must be the last parameter specified, because it includes not only
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the value following the
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.Sq =
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sign, but also passes the rest of the arguments to the command.
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.Pp
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Instead of supplying named
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.Ar parameters ,
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four fixed parameters may be supplied in order on the command line:
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.Ar path ,
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.Ar hostname ,
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.Ar ip ,
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and
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.Ar command .
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As the
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.Va jid
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and
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.Va name
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parameters aren't in this list, this mode will always create a new jail, and
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the
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.Fl c
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and
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.Fl m
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options don't apply (and must not exist).
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.Pp
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Jails have a set a core parameters, and modules can add their own jail
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parameters.
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The current set of available parameters can be retrieved via
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.Dq Nm sysctl Fl d Va security.jail.param .
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The core parameters are:
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.Bl -tag -width indent
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.It Va jid
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The jail identifier.
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This will be assigned automatically to a new jail (or can be explicitly
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set), and can be used to identify the jail for later modification, or
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for such commands as
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.Xr jls 8
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or
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.Xr jexec 8 .
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.It Va name
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The jail name.
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This is an arbitrary string that identifies a jail (except it may not
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contain a
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.Sq \&. ) .
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Like the
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.Va jid ,
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it can be passed to later
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.Nm
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commands, or to
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.Xr jls 8
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or
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.Xr jexec 8 .
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If no
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.Va name
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is supplied, a default is assumed that is the same as the
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.Va jid .
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.It Va path
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Directory which is to be the root of the prison.
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The
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.Va command
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(if any) is run from this directory, as are commands from
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.Xr jexec 8 .
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.It Va ip4.addr
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A comma-separated list of IPv4 addresses assigned to the prison.
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If this is set, the jail is restricted to using only these address.
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Any attempts to use other addresses fail, and attempts to use wildcard
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addresses silently use the jailed address instead.
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For IPv4 the first address given will be kept used as the source address
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in case source address selection on unbound sockets cannot find a better
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match.
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It is only possible to start multiple jails with the same IP address,
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if none of the jails has more than this single overlapping IP address
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assigned to itself.
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.Pp
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A list of zero elements (an empty string) will stop the jail from using IPv4
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entirely; setting the boolean parameter
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.Ar noip4
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will not restrict the jail at all.
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.It Va ip6.addr
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A list of IPv6 addresses assigned to the prison, the counterpart to
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.Ar ip4.addr
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above.
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.It Va host.hostname
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Hostname of the prison.
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Other similar parameters are
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.Va host.domainname ,
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.Va host.hostuuid
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and
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.Va host.hostid .
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Setting the boolean parameter
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.Va nohost
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will retain the system values of these settings.
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.It Va securelevel
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The value of the jail's
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.Va kern.securelevel
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sysctl.
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A jail never has a lower securelevel than the default system, but by
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setting this parameter it may have a higher one.
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If the system securelevel is changed, any jail securelevels will be at
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least as secure.
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.It Va enforce_statfs
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This determines which information processes in a jail are able to get
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about mount points.
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It affects the behaviour of the following syscalls:
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.Xr statfs 2 ,
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.Xr fstatfs 2 ,
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.Xr getfsstat 2
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and
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.Xr fhstatfs 2
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(as well as similar compatibility syscalls).
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When set to 0, all mount points are available without any restrictions.
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When set to 1, only mount points below the jail's chroot directory are
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visible.
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In addition to that, the path to the jail's chroot directory is removed
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from the front of their pathnames.
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When set to 2 (default), above syscalls can operate only on a mount-point
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where the jail's chroot directory is located.
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.It Va persist
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Setting this boolean parameter allows a jail to exist without any
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processes.
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Normally, a jail is destroyed as its last process exits.
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A new jail must have either the
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.Va persist
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parameter or
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.Va command
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pseudo-parameter set.
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.It Va cpuset.id
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The ID of the cpuset associated with this jail (read-only).
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.It Va dying
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This is true if the jail is in the process of shutting down (read-only).
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.It Va parent
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The
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.Va jid
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of the parent of this jail, or zero if this is a top-level jail
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(read-only).
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.It Va allow.*
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Some restrictions of the jail environment may be set on a per-jail
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basis.
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With the exception of
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.Va allow.set_hostname ,
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these boolean parameters are off by default.
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.Bl -tag -width indent
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.It Va allow.set_hostname
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The jail's hostname may be changed via
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.Xr hostname 1
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or
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.Xr sethostname 3 .
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.It Va allow.sysvipc
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A process within the jail has access to System V IPC primitives.
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In the current jail implementation, System V primitives share a single
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namespace across the host and jail environments, meaning that processes
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within a jail would be able to communicate with (and potentially interfere
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with) processes outside of the jail, and in other jails.
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.It Va allow.raw_sockets
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The prison root is allowed to create raw sockets.
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Setting this parameter allows utilities like
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.Xr ping 8
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and
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.Xr traceroute 8
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to operate inside the prison.
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If this is set, the source IP addresses are enforced to comply
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with the IP address bound to the jail, regardless of whether or not
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the
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.Dv IP_HDRINCL
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flag has been set on the socket.
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Since raw sockets can be used to configure and interact with various
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network subsystems, extra caution should be used where privileged access
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to jails is given out to untrusted parties.
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.It Va allow.chflags
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Normally, priveleged users inside a jail are treated as unprivileged by
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.Xr chflags 2 .
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When this parameter is set, such users are treated as privileged, and
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may manipulate system file flags subject to the usual constraints on
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.Va kern.securelevel .
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.It Va allow.mount
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privileged users inside the jail will be able to mount and unmount file
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system types marked as jail-friendly.
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The
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.Xr lsvfs 1
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command can be used to find file system types available for mount from
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within a jail.
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.It Va allow.quotas
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The prison root may administer quotas on the jail's filesystem(s).
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This includes filesystems that the jail may share with other jails or
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with non-jailed parts of the system.
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.It Va allow.socket_af
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Sockets within a jail are normally restricted to IPv4, IPv6, local
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(UNIX), and route. This allows access to other protocol stacks that
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have not had jail functionality added to them.
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.It Va allow.jails
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The prison root may create child jails under this jail. See the
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.Va "Hierarchical Jails"
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section for more information.
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.El
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.El
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.Pp
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Jails are typically set up using one of two philosophies: either to
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constrain a specific application (possibly running with privilege), or
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to create a
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.Dq "virtual system image"
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running a variety of daemons and services.
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In both cases, a fairly complete file system install of
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.Fx
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is
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required, so as to provide the necessary command line tools, daemons,
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libraries, application configuration files, etc.
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However, for a virtual server configuration, a fair amount of
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additional work is required so as to configure the
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.Dq boot
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process.
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This manual page documents the configuration steps necessary to support
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either of these steps, although the configuration steps may be
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refined based on local requirements.
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.Sh EXAMPLES
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.Ss "Setting up a Jail Directory Tree"
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To set up a jail directory tree containing an entire
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.Fx
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distribution, the following
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.Xr sh 1
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command script can be used:
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.Bd -literal
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D=/here/is/the/jail
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cd /usr/src
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mkdir -p $D
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make world DESTDIR=$D
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make distribution DESTDIR=$D
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mount -t devfs devfs $D/dev
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.Ed
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.Pp
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NOTE: It is important that only appropriate device nodes in devfs be
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exposed to a jail; access to disk devices in the jail may permit processes
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in the jail to bypass the jail sandboxing by modifying files outside of
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the jail.
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See
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.Xr devfs 8
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for information on how to use devfs rules to limit access to entries
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in the per-jail devfs.
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A simple devfs ruleset for jails is available as ruleset #4 in
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.Pa /etc/defaults/devfs.rules .
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.Pp
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In many cases this example would put far more in the jail than needed.
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In the other extreme case a jail might contain only one file:
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the executable to be run in the jail.
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.Pp
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We recommend experimentation and caution that it is a lot easier to
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start with a
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.Dq fat
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jail and remove things until it stops working,
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than it is to start with a
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.Dq thin
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jail and add things until it works.
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.Ss "Setting Up a Jail"
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Do what was described in
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.Sx "Setting Up a Jail Directory Tree"
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to build the jail directory tree.
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For the sake of this example, we will
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assume you built it in
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.Pa /data/jail/192.0.2.100 ,
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named for the jailed IP address.
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Substitute below as needed with your
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own directory, IP address, and hostname.
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.Ss "Setting up the Host Environment"
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First, you will want to set up your real system's environment to be
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.Dq jail-friendly .
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For consistency, we will refer to the parent box as the
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.Dq "host environment" ,
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and to the jailed virtual machine as the
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.Dq "jail environment" .
|
|
Since jail is implemented using IP aliases, one of the first things to do
|
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is to disable IP services on the host system that listen on all local
|
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IP addresses for a service.
|
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If a network service is present in the host environment that binds all
|
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available IP addresses rather than specific IP addresses, it may service
|
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requests sent to jail IP addresses if the jail did not bind the port.
|
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This means changing
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.Xr inetd 8
|
|
to only listen on the
|
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appropriate IP address, and so forth.
|
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Add the following to
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.Pa /etc/rc.conf
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in the host environment:
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.Bd -literal -offset indent
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sendmail_enable="NO"
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inetd_flags="-wW -a 192.0.2.23"
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rpcbind_enable="NO"
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.Ed
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.Pp
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.Li 192.0.2.23
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is the native IP address for the host system, in this example.
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Daemons that run out of
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.Xr inetd 8
|
|
can be easily set to use only the specified host IP address.
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Other daemons
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will need to be manually configured\(emfor some this is possible through
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the
|
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.Xr rc.conf 5
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|
flags entries; for others it is necessary to modify per-application
|
|
configuration files, or to recompile the applications.
|
|
The following frequently deployed services must have their individual
|
|
configuration files modified to limit the application to listening
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to a specific IP address:
|
|
.Pp
|
|
To configure
|
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.Xr sshd 8 ,
|
|
it is necessary to modify
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.Pa /etc/ssh/sshd_config .
|
|
.Pp
|
|
To configure
|
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.Xr sendmail 8 ,
|
|
it is necessary to modify
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.Pa /etc/mail/sendmail.cf .
|
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.Pp
|
|
For
|
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.Xr named 8 ,
|
|
it is necessary to modify
|
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.Pa /etc/namedb/named.conf .
|
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.Pp
|
|
In addition, a number of services must be recompiled in order to run
|
|
them in the host environment.
|
|
This includes most applications providing services using
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.Xr rpc 3 ,
|
|
such as
|
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.Xr rpcbind 8 ,
|
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.Xr nfsd 8 ,
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|
and
|
|
.Xr mountd 8 .
|
|
In general, applications for which it is not possible to specify which
|
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IP address to bind should not be run in the host environment unless they
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|
should also service requests sent to jail IP addresses.
|
|
Attempting to serve
|
|
NFS from the host environment may also cause confusion, and cannot be
|
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easily reconfigured to use only specific IPs, as some NFS services are
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hosted directly from the kernel.
|
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Any third-party network software running
|
|
in the host environment should also be checked and configured so that it
|
|
does not bind all IP addresses, which would result in those services' also
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appearing to be offered by the jail environments.
|
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.Pp
|
|
Once
|
|
these daemons have been disabled or fixed in the host environment, it is
|
|
best to reboot so that all daemons are in a known state, to reduce the
|
|
potential for confusion later (such as finding that when you send mail
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|
to a jail, and its sendmail is down, the mail is delivered to the host,
|
|
etc.).
|
|
.Ss "Configuring the Jail"
|
|
Start any jail for the first time without configuring the network
|
|
interface so that you can clean it up a little and set up accounts.
|
|
As
|
|
with any machine (virtual or not) you will need to set a root password, time
|
|
zone, etc.
|
|
Some of these steps apply only if you intend to run a full virtual server
|
|
inside the jail; others apply both for constraining a particular application
|
|
or for running a virtual server.
|
|
.Pp
|
|
Start a shell in the jail:
|
|
.Pp
|
|
.Bd -literal -offset indent
|
|
jail path=/data/jail/192.0.2.100 host.hostname=testhostname \\
|
|
ip4.addr=192.0.2.100 command=/bin/sh
|
|
.Ed
|
|
.Pp
|
|
Assuming no errors, you will end up with a shell prompt within the jail.
|
|
You can now run
|
|
.Pa /usr/sbin/sysinstall
|
|
and do the post-install configuration to set various configuration options,
|
|
or perform these actions manually by editing
|
|
.Pa /etc/rc.conf ,
|
|
etc.
|
|
.Pp
|
|
.Bl -bullet -offset indent -compact
|
|
.It
|
|
Create an empty
|
|
.Pa /etc/fstab
|
|
to quell startup warnings about missing fstab (virtual server only)
|
|
.It
|
|
Disable the port mapper
|
|
.Pa ( /etc/rc.conf :
|
|
.Li rpcbind_enable="NO" )
|
|
(virtual server only)
|
|
.It
|
|
Configure
|
|
.Pa /etc/resolv.conf
|
|
so that name resolution within the jail will work correctly
|
|
.It
|
|
Run
|
|
.Xr newaliases 1
|
|
to quell
|
|
.Xr sendmail 8
|
|
warnings.
|
|
.It
|
|
Disable interface configuration to quell startup warnings about
|
|
.Xr ifconfig 8
|
|
.Pq Li network_interfaces=""
|
|
(virtual server only)
|
|
.It
|
|
Set a root password, probably different from the real host system
|
|
.It
|
|
Set the timezone
|
|
.It
|
|
Add accounts for users in the jail environment
|
|
.It
|
|
Install any packages the environment requires
|
|
.El
|
|
.Pp
|
|
You may also want to perform any package-specific configuration (web servers,
|
|
SSH servers, etc), patch up
|
|
.Pa /etc/syslog.conf
|
|
so it logs as you would like, etc.
|
|
If you are not using a virtual server, you may wish to modify
|
|
.Xr syslogd 8
|
|
in the host environment to listen on the syslog socket in the jail
|
|
environment; in this example, the syslog socket would be stored in
|
|
.Pa /data/jail/192.0.2.100/var/run/log .
|
|
.Pp
|
|
Exit from the shell, and the jail will be shut down.
|
|
.Ss "Starting the Jail"
|
|
You are now ready to restart the jail and bring up the environment with
|
|
all of its daemons and other programs.
|
|
If you are running a single application in the jail, substitute the
|
|
command used to start the application for
|
|
.Pa /etc/rc
|
|
in the examples below.
|
|
To start a virtual server environment,
|
|
.Pa /etc/rc
|
|
is run to launch various daemons and services.
|
|
To do this, first bring up the
|
|
virtual host interface, and then start the jail's
|
|
.Pa /etc/rc
|
|
script from within the jail.
|
|
.Bd -literal -offset indent
|
|
ifconfig ed0 inet alias 192.0.2.100/32
|
|
mount -t procfs proc /data/jail/192.0.2.100/proc
|
|
jail path=/data/jail/192.0.2.100 host.hostname=testhostname \\
|
|
ip4=addr.192.0.2.100 command=/bin/sh /etc/rc
|
|
.Ed
|
|
.Pp
|
|
A few warnings will be produced, because most
|
|
.Xr sysctl 8
|
|
configuration variables cannot be set from within the jail, as they are
|
|
global across all jails and the host environment.
|
|
However, it should all
|
|
work properly.
|
|
You should be able to see
|
|
.Xr inetd 8 ,
|
|
.Xr syslogd 8 ,
|
|
and other processes running within the jail using
|
|
.Xr ps 1 ,
|
|
with the
|
|
.Ql J
|
|
flag appearing beside jailed processes.
|
|
To see an active list of jails, use the
|
|
.Xr jls 8
|
|
utility.
|
|
You should also be able to
|
|
.Xr telnet 1
|
|
to the hostname or IP address of the jailed environment, and log
|
|
in using the accounts you created previously.
|
|
.Pp
|
|
It is possible to have jails started at boot time.
|
|
Please refer to the
|
|
.Dq jail_*
|
|
variables in
|
|
.Xr rc.conf 5
|
|
for more information.
|
|
The
|
|
.Xr rc 8
|
|
jail script provides a flexible system to start/stop jails:
|
|
.Bd -literal
|
|
/etc/rc.d/jail start
|
|
/etc/rc.d/jail stop
|
|
/etc/rc.d/jail start myjail
|
|
/etc/rc.d/jail stop myjail
|
|
.Ed
|
|
.Ss "Managing the Jail"
|
|
Normal machine shutdown commands, such as
|
|
.Xr halt 8 ,
|
|
.Xr reboot 8 ,
|
|
and
|
|
.Xr shutdown 8 ,
|
|
cannot be used successfully within the jail.
|
|
To kill all processes in a
|
|
jail, you may log into the jail and, as root, use one of the following
|
|
commands, depending on what you want to accomplish:
|
|
.Pp
|
|
.Bd -literal -offset indent
|
|
kill -TERM -1
|
|
kill -KILL -1
|
|
.Ed
|
|
.Pp
|
|
This will send the
|
|
.Dv SIGTERM
|
|
or
|
|
.Dv SIGKILL
|
|
signals to all processes in the jail from within the jail.
|
|
Depending on
|
|
the intended use of the jail, you may also want to run
|
|
.Pa /etc/rc.shutdown
|
|
from within the jail.
|
|
To kill processes from outside the jail, use the
|
|
.Xr jexec 8
|
|
utility in conjunction with the one of the
|
|
.Xr kill 1
|
|
commands above.
|
|
You may also remove the jail with
|
|
.Nm
|
|
.Ar -r ,
|
|
which will killall the jail's processes with
|
|
.Dv SIGKILL .
|
|
.Pp
|
|
The
|
|
.Pa /proc/ Ns Ar pid Ns Pa /status
|
|
file contains, as its last field, the name of the jail in which the
|
|
process runs, or
|
|
.Dq Li -
|
|
to indicate that the process is not running within a jail.
|
|
The
|
|
.Xr ps 1
|
|
command also shows a
|
|
.Ql J
|
|
flag for processes in a jail.
|
|
.Pp
|
|
You can also list/kill processes based on their jail ID.
|
|
To show processes and their jail ID, use the following command:
|
|
.Pp
|
|
.Dl "ps ax -o pid,jid,args"
|
|
.Pp
|
|
To show and then kill processes in jail number 3 use the following commands:
|
|
.Bd -literal -offset indent
|
|
pgrep -lfj 3
|
|
pkill -j 3
|
|
.Ed
|
|
or:
|
|
.Pp
|
|
.Dl "killall -j 3"
|
|
.Ss "Jails and File Systems"
|
|
It is not possible to
|
|
.Xr mount 8
|
|
or
|
|
.Xr umount 8
|
|
any file system inside a jail unless the file system is marked
|
|
jail-friendly and the jail's
|
|
.Va allow.mount
|
|
parameter is set.
|
|
.Pp
|
|
Multiple jails sharing the same file system can influence each other.
|
|
For example a user in one jail can fill the file system also
|
|
leaving no space for processes in the other jail.
|
|
Trying to use
|
|
.Xr quota 1
|
|
to prevent this will not work either as the file system quotas
|
|
are not aware of jails but only look at the user and group IDs.
|
|
This means the same user ID in two jails share the same file
|
|
system quota.
|
|
One would need to use one file system per jail to make this work.
|
|
.Ss "Sysctl MIB Entries"
|
|
The read-only entry
|
|
.Va security.jail.jailed
|
|
can be used to determine if a process is running inside a jail (value
|
|
is one) or not (value is zero).
|
|
.Pp
|
|
The variable
|
|
.Va security.jail.max_af_ips
|
|
determines how may address per address family a prison may have.
|
|
The default is 255.
|
|
.Pp
|
|
Some MIB variables have per-jail settings.
|
|
Changes to these variables by a jailed process do not effect the host
|
|
environment, only the jail environment.
|
|
These variables are
|
|
.Va kern.securelevel ,
|
|
.Va kern.hostname ,
|
|
.Va kern.domainname ,
|
|
.Va kern.hostid ,
|
|
and
|
|
.Va kern.hostuuid .
|
|
.Ss "Hierarchical Jails"
|
|
By setting a jail's
|
|
.Va allow.jails
|
|
parameter, processes within a jail may be able to create jails of their own.
|
|
These child jails are kept in a hierarchy, with jails only able to see and/or
|
|
modify the jails they created (or those jails' children).
|
|
Each jail has a read-only
|
|
.Va parent
|
|
parameter, containing the
|
|
.Va jid
|
|
of the jail that created it; a
|
|
.Va jid
|
|
of 0 indicates the jail is a child of the current jail (or is a top-level
|
|
jail if the current process isn't jailed).
|
|
.Pp
|
|
Jailed processes are not allowed to confer greater permissions than they
|
|
themselves are given, e.g. if a jail is created with
|
|
.Va allow.nomount ,
|
|
it is not able to create a jail with
|
|
.Va allow.mount
|
|
set.
|
|
Similarly, such restrictions as
|
|
.Va ip4.addr
|
|
and
|
|
.Va securelevel
|
|
may not be bypassed in child jails.
|
|
.Pp
|
|
A child jail may in turn create its own child jails if its own
|
|
.Va allow.jails
|
|
parameter is set (remember it is off by default).
|
|
These jails are visible to and can be modified by their parent and all
|
|
ancestors.
|
|
.Pp
|
|
Jail names reflect this hierarchy, with a full name being an MIB-type string
|
|
separated by dots.
|
|
For example, if a base system process creates a jail
|
|
.Dq foo ,
|
|
and a process under that jail creates another jail
|
|
.Dq bar ,
|
|
then the second jail will be seen as
|
|
.Dq foo.bar
|
|
in the base system (though it is only seen as
|
|
.Dq bar
|
|
to any processes inside jail
|
|
.Dq foo ) .
|
|
Jids on the other hand exist in a single space, and each jail must have a
|
|
unique jid.
|
|
.Pp
|
|
Like the names, a child jail's
|
|
.Va path
|
|
is relative to its creator's own
|
|
.Va path .
|
|
This is by virtue of the child jail being created in the chrooted
|
|
environment of the first jail.
|
|
.Sh SEE ALSO
|
|
.Xr killall 1 ,
|
|
.Xr lsvfs 1 ,
|
|
.Xr newaliases 1 ,
|
|
.Xr pgrep 1 ,
|
|
.Xr pkill 1 ,
|
|
.Xr ps 1 ,
|
|
.Xr quota 1 ,
|
|
.Xr chroot 2 ,
|
|
.Xr jail_set 2 ,
|
|
.Xr jail_attach 2 ,
|
|
.Xr procfs 5 ,
|
|
.Xr rc.conf 5 ,
|
|
.Xr sysctl.conf 5 ,
|
|
.Xr devfs 8 ,
|
|
.Xr halt 8 ,
|
|
.Xr inetd 8 ,
|
|
.Xr jexec 8 ,
|
|
.Xr jls 8 ,
|
|
.Xr mount 8 ,
|
|
.Xr named 8 ,
|
|
.Xr reboot 8 ,
|
|
.Xr rpcbind 8 ,
|
|
.Xr sendmail 8 ,
|
|
.Xr shutdown 8 ,
|
|
.Xr sysctl 8 ,
|
|
.Xr syslogd 8 ,
|
|
.Xr umount 8
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
utility appeared in
|
|
.Fx 4.0 .
|
|
Hierarchical/extensible jails were introduced in
|
|
.Fx 8.0 .
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
The jail feature was written by
|
|
.An Poul-Henning Kamp
|
|
for R&D Associates
|
|
.Pa http://www.rndassociates.com/
|
|
who contributed it to
|
|
.Fx .
|
|
.Pp
|
|
.An Robert Watson
|
|
wrote the extended documentation, found a few bugs, added
|
|
a few new features, and cleaned up the userland jail environment.
|
|
.Pp
|
|
.An Bjoern A. Zeeb
|
|
added multi-IP jail support for IPv4 and IPv6 based on a patch
|
|
originally done by
|
|
.An Pawel Jakub Dawidek
|
|
for IPv4.
|
|
.Pp
|
|
.An James Gritton
|
|
added the extensible jail parameters and hierchical jails.
|
|
.Sh BUGS
|
|
Jail currently lacks the ability to allow access to
|
|
specific jail information via
|
|
.Xr ps 1
|
|
as opposed to
|
|
.Xr procfs 5 .
|
|
Similarly, it might be a good idea to add an
|
|
address alias flag such that daemons listening on all IPs
|
|
.Pq Dv INADDR_ANY
|
|
will not bind on that address, which would facilitate building a safe
|
|
host environment such that host daemons do not impose on services offered
|
|
from within jails.
|
|
Currently, the simplest answer is to minimize services
|
|
offered on the host, possibly limiting it to services offered from
|
|
.Xr inetd 8
|
|
which is easily configurable.
|