Visit Our UNIX and Linux User Community

JAIL.CONF(5)						      BSD File Formats Manual						      JAIL.CONF(5)

jail.conf -- configuration file for jail(8) DESCRIPTION
A jail(8) configuration file consists of one or more jail definitions statements, and parameter or variable statements within those jail def- initions. A jail definition statement looks something like a C compound statement. A parameter statement looks like a C assignment, includ- ing a terminating semicolon. The general syntax of a jail definition is: jailname { parameter = "value"; parameter = "value"; ... } Each jail is required to have a name at the front of its definition. This is used by jail(8) to specify a jail on the command line and report the jail status, and is also passed to the kernel when creating the jail. Parameters A jail is defined by a set of named parameters, specified inside the jail definition. See jail(8) for a list of jail parameters passed to the kernel, as well as internal parameters used when creating and removing jails. A typical parameter has a name and a value. Some parameters are boolean and may be specified with values of ``true'' or ``false'', or as valueless shortcuts, with a ``no'' prefix indicating a false value. For example, these are equivalent: allow.mount = "false"; allow.nomount; Other parameters may have more than one value. A comma-separated list of values may be set in a single statement, or an existing parameter list may be appended to using ``+='': ip4.addr =,,; ip4.addr =; ip4.addr +=; ip4.addr +=; Note the name parameter is implicitly set to the name in the jail definition. String format Parameter values, including jail names, can be single tokens or quoted strings. A token is any sequence of characters that aren't considered special in the syntax of the configuration file (such as a semicolon or whitespace). If a value contains anything more than letters, num- bers, dots, dashes and underscores, it is advisable to put quote marks around that value. Either single or double quotes may be used. Special characters may be quoted by preceding them with a backslash. Common C-style backslash character codes are also supported, including control characters and octal or hex ASCII codes. A backslash at the end of a line will ignore the subsequent newline and continue the string at the start of the next line. Variables A string may use shell-style variable substitution. A parameter or variable name preceded by a dollar sign, and possibly enclosed in braces, will be replaced with the value of that parameter or variable. For example, a jail's path may be defined in terms of its name or hostname: path = "/var/jail/$name"; path = "/var/jail/${host.hostname}"; Variable substitution occurs in unquoted tokens or in double-quoted strings, but not in single-quote strings. A variable is defined in the same way a parameter is, except that the variable name is preceded with a dollar sign: $parentdir = "/var/jail"; path = "$parentdir/$name"; The difference between parameters and variables is that variables are only used for substitution, while parameters are used both for substi- tution and for passing to the kernel. Wildcards A jail definition with a name of ``*'' is used to define wildcard parameters. Every defined jail will contain both the parameters from its own definition statement, as well as any parameters in a wildcard definition. Variable substitution is done on a per-jail basis, even when that substitution is for a parameter defined in a wildcard section. This is useful for wildcard parameters based on e.g. a jail's name. Later definitions in the configuration file supersede earlier ones, so a wildcard section placed before (above) a jail definition defines parameters that could be changed on a per-jail basis. Or a wildcard section placed after (below) all jails would contain parameters that always apply to every jail. Multiple wildcard statements are allowed, and wildcard parameters may also be specified outside of a jail defi- nition statement. If hierarchical jails are defined, a partial-matching wildcard definition may be specified. For example, a definition with a name of ``foo.*'' would apply to jails with names like ``'' and ``''. Comments The configuration file may contain comments in the common C, C++, and shell formats: /* This is a C style comment. * It may span multiple lines. */ // This is a C++ style comment. # This is a shell style comment. Comments are legal wherever whitespace is allowed, i.e. anywhere except in the middle of a string or a token. EXAMPLES
# Typical static defaults: # Use the rc scripts to start and stop jails. Mount jail's /dev. exec.start = "/bin/sh /etc/rc"; exec.stop = "/bin/sh /etc/rc.shutdown"; exec.clean; mount.devfs; # Dynamic wildcard parameter: # Base the path off the jail name. path = "/var/jail/$name"; # A typical jail. foo { host.hostname = ""; ip4.addr =,,; } # This jail overrides the defaults defined above. bar { exec.start = ''; exec.stop = ''; path = /; mount.nodevfs; persist; // Required because there are no processes } SEE ALSO
jail_set(2), rc.conf(5), jail(8), jls(8) HISTORY
The jail(8) utility appeared in FreeBSD 4.0. The jail.conf file was added in FreeBSD 9.1. AUTHORS
The jail feature was written by Poul-Henning Kamp for R&D Associates who contributed it to FreeBSD. James Gritton added the extensible jail parameters and configuration file. BSD
February 13, 2014 BSD

Featured Tech Videos