SYNOPSIS

su [options] [username]

DESCRIPTION

OPTIONS

The options which apply to the su command are:

-c, --command COMMAND

Specify a command that will be invoked by the shell using its -c.

The executed command will have no controlling terminal. This option cannot be used to execute interractive programs which need a controlling TTY.

-, -l, --login

Provide an environment similar to what the user would expect had the user logged in directly.

When - is used, it must be specified before any username. For portability it is recommended to use it as last option, before any username. The other forms (-l and --login) do not have this restriction.

-s, --shell SHELL

The shell that will be invoked.

The invoked shell is chosen from (highest priority first):

The shell specified with --shell.

If --preserve-environment is used, the shell specified by the $SHELL environment variable.

The shell indicated in the /etc/passwd entry for the target user.

/bin/sh if a shell could not be found by any above method.

If the target user has a restricted shell (i.e. the shell field of this user's entry in /etc/passwd is not listed in /etc/shells), then the --shell option or the $SHELL environment variable won't be taken into account, unless su is called by root.

-m, -p, --preserve-environment

Preserve the current environment, except for:

$PATH

reset according to the /etc/login.defs options ENV_PATH or ENV_SUPATH (see below);

$IFS

reset to "<space><tab><newline>", if it was set.

If the target user has a restricted shell, this option has no effect (unless su is called by root).

Note that the default behavior for the environment is the following:

The $HOME, $SHELL, $USER, $LOGNAME, $PATH, and $IFS environment variables are reset.

If --login is not used, the environment is copied, except for the variables above.

If --login is used, the $TERM, $COLORTERM, $DISPLAY, and $XAUTHORITY environment variables are copied if they were set.

Other environments might be set by PAM modules.

CAVEATS

This version of su has many compilation options, only some of which may be in use at any particular site.

CONFIGURATION

The following configuration variables in /etc/login.defs change the behavior of this tool:

CONSOLE_GROUPS (string)

List of groups to add to the user's supplementary groups set when logging in on the console (as determined by the CONSOLE setting). Default is none.

Use with caution - it is possible for users to gain permanent access to these groups, even when not logged in on the console.

DEFAULT_HOME (boolean)

Indicate if login is allowed if we can't cd to the home directory. Default is no.

If set to yes, the user will login in the root (/) directory if it is not possible to cd to her home directory.

ENV_PATH (string)

If set, it will be used to define the PATH environment variable when a regular user login. The value is a colon separated list of paths (for example /bin:/usr/bin) and can be preceded by PATH=. The default value is PATH=/bin:/usr/bin.

ENV_SUPATH (string)

If set, it will be used to define the PATH environment variable when the superuser login. The value is a colon separated list of paths (for example /sbin:/bin:/usr/sbin:/usr/bin) and can be preceded by PATH=. The default value is PATH=/sbin:/bin:/usr/sbin:/usr/bin.

SULOG_FILE (string)

If defined, all su activity is logged to this file.

SU_NAME (string)

If defined, the command name to display when running "su -". For example, if this is defined as "su" then a "ps" will display the command is "-su". If not defined, then "ps" would display the name of the shell actually being run, e.g. something like "-sh".

SYSLOG_SU_ENAB (boolean)

Enable "syslog" logging of su activity - in addition to sulog file logging.

FILES

/etc/passwd

User account information.

/etc/shadow

Secure user account information.

/etc/login.defs

Shadow password suite configuration.