/
jail.8
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jail.8
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.\" Copyright (c) 2000, 2003 Robert N. M. Watson
.\" Copyright (c) 2008-2012 James Gritton
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd August 4, 2014
.Dt JAIL 8
.Os
.Sh NAME
.Nm jail
.Nd "manage system jails"
.Sh SYNOPSIS
.Nm
.Op Fl dhilqv
.Op Fl J Ar jid_file
.Op Fl u Ar username
.Op Fl U Ar username
.Op Fl cmr
.Ar param Ns = Ns Ar value ...
.Op Cm command Ns = Ns Ar command ...
.Nm
.Op Fl dqv
.Op Fl f Ar conf_file
.Op Fl p Ar limit
.Op Fl cmr
.Op Ar jail
.Nm
.Op Fl qv
.Op Fl f Ar conf_file
.Op Fl rR
.Op Cm * | Ar jail ...
.Nm
.Op Fl dhilqv
.Op Fl J Ar jid_file
.Op Fl u Ar username
.Op Fl U Ar username
.Op Fl n Ar jailname
.Op Fl s Ar securelevel
.Op Ar path hostname [ Ar ip Ns [ Ns Ar ,... Ns ]] Ar command ...
.Sh DESCRIPTION
The
.Nm
utility creates new jails, or modifies or removes existing jails.
A jail
.Pq or Dq prison
is specified via parameters on the command line, or in the
.Xr jail.conf 5
file.
.Pp
At least one of the options
.Fl c ,
.Fl m
or
.Fl r
must be specified.
These options are used alone or in combination to describe the operation to
perform:
.Bl -tag -width indent
.It Fl c
Create a new jail.
The jail
.Va jid
and
.Va name
parameters (if specified on the command line)
must not refer to an existing jail.
.It Fl m
Modify an existing jail.
One of the
.Va jid
or
.Va name
parameters must exist and refer to an existing jail.
Some parameters may not be changed on a running jail.
.It Fl r
Remove the
.Ar jail
specified by jid or name.
All jailed processes are killed, and all jails that are
children of this jail are also
removed.
.It Fl rc
Restart an existing jail.
The jail is first removed and then re-created, as if
.Dq Nm Fl r
and
.Dq Nm Fl c
were run in succession.
.It Fl cm
Create a jail if it does not exist, or modify the jail if it does exist.
.It Fl mr
Modify an existing jail.
The jail may be restarted if necessary to modify parameters than could
not otherwise be changed.
.It Fl cmr
Create a jail if it doesn't exist, or modify (and possibly restart) the
jail if it does exist.
.El
.Pp
Other available options are:
.Bl -tag -width indent
.It Fl d
Allow making changes to a dying jail, equivalent to the
.Va allow.dying
parameter.
.It Fl f Ar conf_file
Use configuration file
.Ar conf_file
instead of the default
.Pa /etc/jail.conf .
.It Fl h
Resolve the
.Va host.hostname
parameter (or
.Va hostname )
and add all IP addresses returned by the resolver
to the list of addresses for this jail.
This is equivalent to the
.Va ip_hostname
parameter.
.It Fl i
Output (only) the jail identifier of the newly created jail(s).
This implies the
.Fl q
option.
.It Fl J Ar jid_file
Write a
.Ar jid_file
file, containing the parameters used to start the jail.
.It Fl l
Run commands in a clean environment.
This is deprecated and is equivalent to the exec.clean parameter.
.It Fl n Ar jailname
Set the jail's name.
This is deprecated and is equivalent to the
.Va name
parameter.
.It Fl p Ar limit
Limit the number of commands from
.Va exec.*
that can run simultaneously.
.It Fl q
Suppress the message printed whenever a jail is created, modified or removed.
Only error messages will be printed.
.It Fl R
A variation of the
.Fl r
option that removes an existing jail without using the configuration file.
No removal-related parameters for this jail will be used \(em the jail will
simply be removed.
.It Fl s Ar securelevel
Set the
.Va kern.securelevel
MIB entry to the specified value inside the newly created jail.
This is deprecated and is equivalent to the
.Va securelevel
parameter.
.It Fl u Ar username
The user name from host environment as whom jailed commands should run.
This is deprecated and is equivalent to the
.Va exec.jail_user
and
.Va exec.system_jail_user
parameters.
.It Fl U Ar username
The user name from the jailed environment as whom jailed commands should run.
This is deprecated and is equivalent to the
.Va exec.jail_user
parameter.
.It Fl v
Print a message on every operation, such as running commands and
mounting filesystems.
.El
.Pp
If no arguments are given after the options, the operation (except
remove) will be performed on all jails specified in the
.Xr jail.conf 5
file.
A single argument of a jail name will operate only on the specified jail.
The
.Fl r
and
.Fl R
options can also remove running jails that aren't in the
.Xr jail.conf 5
file, specified by name or jid.
.Pp
An argument of
.Dq *
is a wildcard that will operate on all jails, regardless of whether
they appear in
.Xr jail.conf 5 ;
this is the surest way for
.Fl r
to remove all jails.
If hierarchical jails exist, a partial-matching wildcard definition may
be specified.
For example, an argument of
.Dq foo.*
would apply to jails with names like
.Dq foo.bar
and
.Dq foo.bar.baz .
.Pp
A jail may be specified with parameters directly on the command line.
In this case, the
.Xr jail.conf 5
file will not be used.
For backward compatibility, the command line may also have four fixed
parameters, without names:
.Ar path ,
.Ar hostname ,
.Ar ip ,
and
.Ar command .
This mode will always create a new jail, and the
.Fl c
and
.Fl m
options do not apply (and must not be present).
.Ss Jail Parameters
Parameters in the
.Xr jail.conf 5
file, or on the command line, are generally of the form
.Dq name=value .
Some parameters are boolean, and do not have a value but are set by the
name alone with or without a
.Dq no
prefix, e.g.
.Va persist
or
.Va nopersist .
They can also be given the values
.Dq true
and
.Dq false .
Other parameters may have more than one value, specified as a
comma-separated list or with
.Dq +=
in the configuration file (see
.Xr jail.conf 5
for details).
.Pp
The
.Nm
utility recognizes two classes of parameters.
There are the true jail
parameters that are passed to the kernel when the jail is created,
which can be seen with
.Xr jls 8 ,
and can (usually) be changed with
.Dq Nm Fl m .
Then there are pseudo-parameters that are only used by
.Nm
itself.
.Pp
Jails have a set a core parameters, and kernel modules can add their own
jail parameters.
The current set of available parameters can be retrieved via
.Dq Nm sysctl Fl d Va security.jail.param .
Any parameters not set will be given default values, often based on the
current environment.
The core parameters are:
.Bl -tag -width indent
.It Va jid
The jail identifier.
This will be assigned automatically to a new jail (or can be explicitly
set), and can be used to identify the jail for later modification, or
for such commands as
.Xr jls 8
or
.Xr jexec 8 .
.It Va name
The jail name.
This is an arbitrary string that identifies a jail (except it may not
contain a
.Sq \&. ) .
Like the
.Va jid ,
it can be passed to later
.Nm
commands, or to
.Xr jls 8
or
.Xr jexec 8 .
If no
.Va name
is supplied, a default is assumed that is the same as the
.Va jid .
The
.Va name
parameter is implied by the
.Xr jail.conf 5
file format, and need not be explicitly set when using the configuration
file.
.It Va path
The directory which is to be the root of the jail.
Any commands run inside the jail, either by
.Nm
or from
.Xr jexec 8 ,
are run from this directory.
.It Va ip4.addr
A list of IPv4 addresses assigned to the jail.
If this is set, the jail is restricted to using only these addresses.
Any attempts to use other addresses fail, and attempts to use wildcard
addresses silently use the jailed address instead.
For IPv4 the first address given will be used as the source address
when source address selection on unbound sockets cannot find a better
match.
It is only possible to start multiple jails with the same IP address
if none of the jails has more than this single overlapping IP address
assigned to itself.
.It Va ip4.saddrsel
A boolean option to change the formerly mentioned behaviour and disable
IPv4 source address selection for the jail in favour of the primary
IPv4 address of the jail.
Source address selection is enabled by default for all jails and the
.Va ip4.nosaddrsel
setting of a parent jail is not inherited for any child jails.
.It Va ip4
Control the availability of IPv4 addresses.
Possible values are
.Dq inherit
to allow unrestricted access to all system addresses,
.Dq new
to restrict addresses via
.Va ip4.addr ,
and
.Dq disable
to stop the jail from using IPv4 entirely.
Setting the
.Va ip4.addr
parameter implies a value of
.Dq new .
.It Va ip6.addr , Va ip6.saddrsel , Va ip6
A set of IPv6 options for the jail, the counterparts to
.Va ip4.addr ,
.Va ip4.saddrsel
and
.Va ip4
above.
.It vnet
Create the jail with its own virtual network stack,
with its own network interfaces, addresses, routing table, etc.
The kernel must have been compiled with the
.Sy VIMAGE option
for this to be available.
Possible values are
.Dq inherit
to use the system network stack, possibly with restricted IP addresses,
and
.Dq new
to create a new network stack.
.It Va host.hostname
The hostname of the jail.
Other similar parameters are
.Va host.domainname ,
.Va host.hostuuid
and
.Va host.hostid .
.It Va host
Set the origin of hostname and related information.
Possible values are
.Dq inherit
to use the system information and
.Dq new
for the jail to use the information from the above fields.
Setting any of the above fields implies a value of
.Dq new .
.It Va securelevel
The value of the jail's
.Va kern.securelevel
sysctl.
A jail never has a lower securelevel than its parent system, but by
setting this parameter it may have a higher one.
If the system securelevel is changed, any jail securelevels will be at
least as secure.
.It Va devfs_ruleset
The number of the devfs ruleset that is enforced for mounting devfs in
this jail.
A value of zero (default) means no ruleset is enforced.
Descendant jails inherit the parent jail's devfs ruleset enforcement.
Mounting devfs inside a jail is possible only if the
.Va allow.mount
and
.Va allow.mount.devfs
permissions are effective and
.Va enforce_statfs
is set to a value lower than 2.
Devfs rules and rulesets cannot be viewed or modified from inside a jail.
.Pp
NOTE: It is important that only appropriate device nodes in devfs be
exposed to a jail; access to disk devices in the jail may permit processes
in the jail to bypass the jail sandboxing by modifying files outside of
the jail.
See
.Xr devfs 8
for information on how to use devfs rules to limit access to entries
in the per-jail devfs.
A simple devfs ruleset for jails is available as ruleset #4 in
.Pa /etc/defaults/devfs.rules .
.It Va children.max
The number of child jails allowed to be created by this jail (or by
other jails under this jail).
This limit is zero by default, indicating the jail is not allowed to
create child jails.
See the
.Sx "Hierarchical Jails"
section for more information.
.It Va children.cur
The number of descendants of this jail, including its own child jails
and any jails created under them.
.It Va enforce_statfs
This determines what information processes in a jail are able to get
about mount points.
It affects the behaviour of the following syscalls:
.Xr statfs 2 ,
.Xr fstatfs 2 ,
.Xr getfsstat 2 ,
and
.Xr fhstatfs 2
(as well as similar compatibility syscalls).
When set to 0, all mount points are available without any restrictions.
When set to 1, only mount points below the jail's chroot directory are
visible.
In addition to that, the path to the jail's chroot directory is removed
from the front of their pathnames.
When set to 2 (default), above syscalls can operate only on a mount-point
where the jail's chroot directory is located.
.It Va persist
Setting this boolean parameter allows a jail to exist without any
processes.
Normally, a command is run as part of jail creation, and then the jail
is destroyed as its last process exits.
A new jail must have either the
.Va persist
parameter or
.Va exec.start
or
.Va command
pseudo-parameter set.
.It Va cpuset.id
The ID of the cpuset associated with this jail (read-only).
.It Va dying
This is true if the jail is in the process of shutting down (read-only).
.It Va parent
The
.Va jid
of the parent of this jail, or zero if this is a top-level jail
(read-only).
.It Va allow.*
Some restrictions of the jail environment may be set on a per-jail
basis.
With the exception of
.Va allow.set_hostname ,
these boolean parameters are off by default.
.Bl -tag -width indent
.It Va allow.set_hostname
The jail's hostname may be changed via
.Xr hostname 1
or
.Xr sethostname 3 .
.It Va allow.sysvipc
A process within the jail has access to System V IPC primitives.
In the current jail implementation, System V primitives share a single
namespace across the host and jail environments, meaning that processes
within a jail would be able to communicate with (and potentially interfere
with) processes outside of the jail, and in other jails.
.It Va allow.raw_sockets
The jail root is allowed to create raw sockets.
Setting this parameter allows utilities like
.Xr ping 8
and
.Xr traceroute 8
to operate inside the jail.
If this is set, the source IP addresses are enforced to comply
with the IP address bound to the jail, regardless of whether or not
the
.Dv IP_HDRINCL
flag has been set on the socket.
Since raw sockets can be used to configure and interact with various
network subsystems, extra caution should be used where privileged access
to jails is given out to untrusted parties.
.It Va allow.chflags
Normally, privileged users inside a jail are treated as unprivileged by
.Xr chflags 2 .
When this parameter is set, such users are treated as privileged, and
may manipulate system file flags subject to the usual constraints on
.Va kern.securelevel .
.It Va allow.mount
privileged users inside the jail will be able to mount and unmount file
system types marked as jail-friendly.
The
.Xr lsvfs 1
command can be used to find file system types available for mount from
within a jail.
This permission is effective only if
.Va enforce_statfs
is set to a value lower than 2.
.It Va allow.mount.devfs
privileged users inside the jail will be able to mount and unmount the
devfs file system.
This permission is effective only together with
.Va allow.mount
and only when
.Va enforce_statfs
is set to a value lower than 2.
The devfs ruleset should be restricted from the default by using the
.Va devfs_ruleset
option.
.It Va allow.mount.nullfs
privileged users inside the jail will be able to mount and unmount the
nullfs file system.
This permission is effective only together with
.Va allow.mount
and only when
.Va enforce_statfs
is set to a value lower than 2.
.It Va allow.mount.procfs
privileged users inside the jail will be able to mount and unmount the
procfs file system.
This permission is effective only together with
.Va allow.mount
and only when
.Va enforce_statfs
is set to a value lower than 2.
.It Va allow.mount.tmpfs
privileged users inside the jail will be able to mount and unmount the
tmpfs file system.
This permission is effective only together with
.Va allow.mount
and only when
.Va enforce_statfs
is set to a value lower than 2.
.It Va allow.mount.zfs
privileged users inside the jail will be able to mount and unmount the
ZFS file system.
This permission is effective only together with
.Va allow.mount
and only when
.Va enforce_statfs
is set to a value lower than 2.
See
.Xr zfs 8
for information on how to configure the ZFS filesystem to operate from
within a jail.
.It Va allow.quotas
The jail root may administer quotas on the jail's filesystem(s).
This includes filesystems that the jail may share with other jails or
with non-jailed parts of the system.
.It Va allow.socket_af
Sockets within a jail are normally restricted to IPv4, IPv6, local
(UNIX), and route. This allows access to other protocol stacks that
have not had jail functionality added to them.
.El
.El
.Pp
There are pseudo-parameters that are not passed to the kernel, but are
used by
.Nm
to set up the jail environment, often by running specified commands
when jails are created or removed.
The
.Va exec.*
command parameters are
.Xr sh 1
command lines that are run in either the system or jail environment.
They may be given multiple values, which run would the specified
commands in sequence.
All commands must succeed (return a zero exit status), or the jail will
not be created or removed, as appropriate.
.Pp
The pseudo-parameters are:
.Bl -tag -width indent
.It Va exec.prestart
Command(s) to run in the system environment before a jail is created.
.It Va exec.start
Command(s) to run in the jail environment when a jail is created.
A typical command to run is
.Dq sh /etc/rc .
.It Va command
A synonym for
.Va exec.start
for use when specifying a jail directly on the command line.
Unlike other parameters whose value is a single string,
.Va command
uses the remainder of the
.Nm
command line as its own arguments.
.It Va exec.poststart
Command(s) to run in the system environment after a jail is created,
and after any
.Va exec.start
commands have completed.
.It Va exec.prestop
Command(s) to run in the system environment before a jail is removed.
.It Va exec.stop
Command(s) to run in the jail environment before a jail is removed,
and after any
.Va exec.prestop
commands have completed.
A typical command to run is
.Dq sh /etc/rc.shutdown .
.It Va exec.poststop
Command(s) to run in the system environment after a jail is removed.
.It Va exec.clean
Run commands in a clean environment.
The environment is discarded except for
.Ev HOME , SHELL , TERM
and
.Ev USER .
.Ev HOME
and
.Ev SHELL
are set to the target login's default values.
.Ev USER
is set to the target login.
.Ev TERM
is imported from the current environment.
The environment variables from the login class capability database for the
target login are also set.
.It Va exec.jail_user
The user to run commands as, when running in the jail environment.
The default is to run the commands as the current user.
.It Va exec.system_jail_user
This boolean option looks for the
.Va exec.jail_user
in the system
.Xr passwd 5
file, instead of in the jail's file.
.It Va exec.system_user
The user to run commands as, when running in the system environment.
The default is to run the commands as the current user.
.It Va exec.timeout
The maximum amount of time to wait for a command to complete, in
seconds.
If a command is still running after this timeout has passed,
the jail will not be created or removed, as appropriate.
.It Va exec.consolelog
A file to direct command output (stdout and stderr) to.
.It Va exec.fib
The FIB (routing table) to set when running commands inside the jail.
.It Va stop.timeout
The maximum amount of time to wait for a jail's processes to exit
after sending them a
.Dv SIGTERM
signal (which happens after the
.Va exec.stop
commands have completed).
After this many seconds have passed, the jail will be removed, which
will kill any remaining processes.
If this is set to zero, no
.Dv SIGTERM
is sent and the jail is immediately removed.
The default is 10 seconds.
.It Va interface
A network interface to add the jail's IP addresses
.Va ( ip4.addr
and
.Va ip6.addr )
to.
An alias for each address will be added to the interface before the
jail is created, and will be removed from the interface after the
jail is removed.
.It Va ip4.addr
In addition to the IP addresses that are passed to the kernel, an
interface, netmask and additional paramters (as supported by
.Xr ifconfig 8 Ns )
may also be specified, in the form
.Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
If an interface is given before the IP address, an alias for the address
will be added to that interface, as it is with the
.Va interface
parameter.
If a netmask in either dotted-quad or CIDR form is given
after an IP address, it will be used when adding the IP alias.
If additional parameters are specified then they will also be used when
adding the IP alias.
.It Va ip6.addr
In addition to the IP addresses that are passed to the kernel,
an interface, prefix and additional parameters (as supported by
.Xr ifconfig 8 Ns )
may also be specified, in the form
.Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
.It Va vnet.interface
A network interface to give to a vnet-enabled jail after is it created.
The interface will automatically be released when the jail is removed.
.It Va ip_hostname
Resolve the
.Va host.hostname
parameter and add all IP addresses returned by the resolver
to the list of addresses
.Po Va ip4.addr
or
.Va ip6.addr Pc
for this jail.
This may affect default address selection for outgoing IPv4 connections
from jails.
The address first returned by the resolver for each address family
will be used as the primary address.
.It Va mount
A filesystem to mount before creating the jail (and to unmount after
removing it), given as a single
.Xr fstab 5
line.
.It Va mount.fstab
An
.Xr fstab 5
format file containing filesystems to mount before creating a jail.
.It Va mount.devfs
Mount a
.Xr devfs 5
filesystem on the chrooted
.Pa /dev
directory, and apply the ruleset in the
.Va devfs_ruleset
parameter (or a default of ruleset 4: devfsrules_jail)
to restrict the devices visible inside the jail.
.It Va mount.fdescfs
Mount a
.Xr fdescfs 5
filesystem on the chrooted
.Pa /dev/fd
directory.
.It Va allow.dying
Allow making changes to a
.Va dying
jail.
.It Va depend
Specify a jail (or jails) that this jail depends on.
Any such jails must be fully created, up to the last
.Va exec.poststart
command, before any action will taken to create this jail.
When jails are removed the opposite is true:
this jail must be fully removed, up to the last
.Va exec.poststop
command, before the jail(s) it depends on are stopped.
.El
.Sh EXAMPLES
Jails are typically set up using one of two philosophies: either to
constrain a specific application (possibly running with privilege), or
to create a
.Dq "virtual system image"
running a variety of daemons and services.
In both cases, a fairly complete file system install of
.Fx
is
required, so as to provide the necessary command line tools, daemons,
libraries, application configuration files, etc.
However, for a virtual server configuration, a fair amount of
additional work is required so as to replace the
.Dq boot
process.
This manual page documents the configuration steps necessary to support
either of these steps, although the configuration steps may need to be
refined based on local requirements.
.Ss "Setting up a Jail Directory Tree"
To set up a jail directory tree containing an entire
.Fx
distribution, the following
.Xr sh 1
command script can be used:
.Bd -literal
D=/here/is/the/jail
cd /usr/src
mkdir -p $D
make world DESTDIR=$D
make distribution DESTDIR=$D
.Ed
.Pp
In many cases this example would put far more in the jail than needed.
In the other extreme case a jail might contain only one file:
the executable to be run in the jail.
.Pp
We recommend experimentation, and caution that it is a lot easier to
start with a
.Dq fat
jail and remove things until it stops working,
than it is to start with a
.Dq thin
jail and add things until it works.
.Ss "Setting Up a Jail"
Do what was described in
.Sx "Setting Up a Jail Directory Tree"
to build the jail directory tree.
For the sake of this example, we will
assume you built it in
.Pa /data/jail/testjail ,
for a jail named
.Dq testjail .
Substitute below as needed with your
own directory, IP address, and hostname.
.Ss "Setting up the Host Environment"
First, set up the real system's environment to be
.Dq jail-friendly .
For consistency, we will refer to the parent box as the
.Dq "host environment" ,
and to the jailed virtual machine as the
.Dq "jail environment" .
Since jails are implemented using IP aliases, one of the first things to do
is to disable IP services on the host system that listen on all local
IP addresses for a service.
If a network service is present in the host environment that binds all
available IP addresses rather than specific IP addresses, it may service
requests sent to jail IP addresses if the jail did not bind the port.
This means changing
.Xr inetd 8
to only listen on the
appropriate IP address, and so forth.
Add the following to
.Pa /etc/rc.conf
in the host environment:
.Bd -literal -offset indent
sendmail_enable="NO"
inetd_flags="-wW -a 192.0.2.23"
rpcbind_enable="NO"
.Ed
.Pp
.Li 192.0.2.23
is the native IP address for the host system, in this example.
Daemons that run out of
.Xr inetd 8
can be easily configured to use only the specified host IP address.
Other daemons
will need to be manually configured \(em for some this is possible through
.Xr rc.conf 5
flags entries; for others it is necessary to modify per-application
configuration files, or to recompile the application.
The following frequently deployed services must have their individual
configuration files modified to limit the application to listening
to a specific IP address:
.Pp
To configure
.Xr sshd 8 ,
it is necessary to modify
.Pa /etc/ssh/sshd_config .
.Pp
To configure
.Xr sendmail 8 ,
it is necessary to modify
.Pa /etc/mail/sendmail.cf .
.Pp
For
.Xr named 8 ,
it is necessary to modify
.Pa /etc/namedb/named.conf .
.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
.Xr rpc 3 ,
such as
.Xr rpcbind 8 ,
.Xr nfsd 8 ,
and
.Xr mountd 8 .
In general, applications for which it is not possible to specify which
IP address to bind should not be run in the host environment unless they
should also service requests sent to jail IP addresses.
Attempting to serve
NFS from the host environment may also cause confusion, and cannot be
easily reconfigured to use only specific IPs, as some NFS services are
hosted directly from the kernel.
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
appearing to be offered by the jail environments.
.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
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:
.Bd -literal -offset indent
jail -c path=/data/jail/testjail mount.devfs 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
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
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/testjail/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.
Create an entry for the jail in
.Pa /etc/jail.conf :
.Bd -literal -offset indent
testjail {
path = /tmp/jail/testjail;
mount.devfs;
host.hostname = testhostname;
ip4.addr = 192.0.2.100;
interface = ed0;
exec.start = "/bin/sh /etc/rc";
exec.stop = "/bin/sh /etc/rc.shutdown";
}
.Ed
.Pp
To start a virtual server environment,
.Pa /etc/rc
is run to launch various daemons and services, and
.Pa /etc/rc.shutdown
is run to shut them down when the jail is removed.
If you are running a single application in the jail,
substitute the command used to start the application for
.Dq /bin/sh /etc/rc ;
there may be some script available to cleanly shut down the application,
or it may be sufficient to go without a stop command, and have
.Nm
send
.Dv SIGTERM
to the application.
.Pp
Start the jail by running:
.Bd -literal -offset indent
jail -c testjail
.Ed
.Pp
A few warnings may be produced; 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