NAME
su - change user ID or become superuser
SYNOPSIS
su [options] [username]
DESCRIPTION
The su command is used to become another user during a login session. Invoked without a username, su defaults to becoming the superuser. The optional argument - may be used to provide an environment similar to what the user would expect had the user logged in directly. Additional arguments may be provided after the username, in which case they are supplied to the user's login shell. In particular, an argument of -c will cause the next argument to be treated as a command by most command interpreters. The command will be executed by the shell specified in /etc/passwd for the target user. You can use the -- argument to separate su options from the arguments supplied to the shell. The user will be prompted for a password, if appropriate. Invalid passwords will produce an error message. All attempts, both valid and invalid, are logged to detect abuse of the system. The current environment is passed to the new shell. The value of $PATH is reset to /bin:/usr/bin for normal users, or /sbin:/bin:/usr/sbin:/usr/bin for the superuser. This may be changed with the ENV_PATH and ENV_SUPATH definitions in /etc/login.defs. A subsystem login is indicated by the presence of a "*" as the first character of the login shell. The given home directory will be used as the root of a new file system which the user is actually logged into.
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.
EXIT VALUES
On success, su returns the exit value of the command it executed. If this command was terminated by a signal, su returns the number of this signal plus 128. If su has to kill the command (because it was asked to terminate, and the command did not terminate in time), su returns 255. Some exit values from su are independent from the executed command: 0 success (--help only) 1 System or authentication failure 126 The requested command was not found 127 The requested command could not be executed
SEE ALSO
login(1), login.defs(5), sg(1), sh(1).
More Linux Commands
manpages/sched_getparam.2.html
sched_getparam(2) - set and get scheduling parameters.......
sched_setparam() sets the scheduling parameters associated with the scheduling policy for the process identified by pid. If pid is zero, then the parameters of
manpages/XtMoveWidget.3.html
XtMoveWidget(3) - move and resize widgets - Linux man page
The XtConfigureWidget function returns immediately if the specified geometry fields are the same as the old values. Otherwise, XtConfigureWidget writes the new
manpages/XGetKeyboardControl.3.html
XGetKeyboardControl(3) - manipulate keyboard settings and ke
The XChangeKeyboardControl function controls the keyboard characteristics defined by the XKeyboardControl structure. The value_mask argument specifies which val
manpages/gkeytool.1.html
gkeytool(1) - Manage private keys and public certificates...
Cryptographic credentials, in a Java environment, are usually stored in a Key Store. The Java SDK specifies a Key Store as a persistent container of two types o
manpages/gtk-encode-symbolic-svg.1.html
gtk-encode-symbolic-svg(1) Symbolic icon conversion utility
gtk-encode-symbolic-svg converts symbolic svg icons into specially prepared png files. GTK+ can load and recolor these pngs, just like original svgs, but loadin
manpages/poweroff.8.html
poweroff(8) - Halt, power-off or reboot the machine.........
poweroff.8 - halt, poweroff, reboot may be used to halt, power-off or reboot the machine. OPTIONS The following options are understood: --help Print a short hel
manpages/keyctl_get_persistent.3.html
keyctl_get_persistent(3) Get the persistent keyring for a us
keyctl_get_persistent() gets the persistent keyring for the specified user ID. Unlike the session and user keyrings, this keyring will persist once all login se
manpages/program_invocation_short_name.3.html
program_invocation_short_name(3) - obtain name used to invok
program_invocation_name contains the name that was used to invoke the calling program. This is the same as the value of argv[0] in main(), with the difference t
manpages/yuvfps.1.html
yuvfps(1) - Converts to a different frame rate (Man Page)...
yuvfps is a general (UP or DOWN) resampling utility that is provided to allow the generation of video streams with the frame rates required for each standard vi
manpages/tputs.3ncurses.html
tputs(3ncurses) - curses interfaces to terminfo database....
These low-level routines must be called by programs that have to deal directly with the terminfo database to handle certain terminal capabilities, such as progr
manpages/htole32.3.html
htole32(3) - convert values between host and big-/little-end
These functions convert the byte encoding of integer values from the byte order that the current CPU (the host) uses, to and from little-endian and big-endian b
manpages/napms.3ncurses.html
napms(3ncurses) - low-level curses routines - Linux man page
The following routines give low-level access to various curses capabilities. These routines typically are used inside library routines. The def_prog_mode and de
