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.\" Author: Julianne Frances Haugh
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.\" Generator: DocBook XSL Stylesheets v1.76.1 <http://docbook.sf.net/>
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.\" Manual: User Commands
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.\" Source: shadow-utils 4.1.5.1
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.TH "SU" "1" "05/25/2012" "shadow\-utils 4\&.1\&.5\&.1" "User Commands"
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.\" * Define some portability stuff
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.\" http://bugs.debian.org/507673
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.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.\" * MAIN CONTENT STARTS HERE *
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su \- change user ID or become superuser
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\fBsu\fR [\fIoptions\fR] [\fIusername\fR]
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command is used to become another user during a login session\&. Invoked without a
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defaults to becoming the superuser\&. The optional argument
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may be used to provide an environment similar to what the user would expect had the user logged in directly\&.
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Additional arguments may be provided after the username, in which case they are supplied to the user\*(Aqs login shell\&. In particular, an argument of
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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
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for the target user\&.
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options from the arguments supplied to the shell\&.
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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\&.
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The current environment is passed to the new shell\&. The value of
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/sbin:/bin:/usr/sbin:/usr/bin
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for the superuser\&. This may be changed with the
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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\&.
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The options which apply to the
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\fB\-c\fR, \fB\-\-command\fR \fICOMMAND\fR
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Specify a command that will be invoked by the shell using its
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The executed command will have no controlling terminal\&. This option cannot be used to execute interractive programs which need a controlling TTY\&.
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\fB\-\fR, \fB\-l\fR, \fB\-\-login\fR
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Provide an environment similar to what the user would expect had the user logged in directly\&.
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is used, it must be specified as the last
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option\&. The other forms (\fB\-l\fR
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\fB\-\-login\fR) do not have this restriction\&.
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\fB\-s\fR, \fB\-\-shell\fR \fISHELL\fR
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The shell that will be invoked\&.
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The invoked shell is chosen from (highest priority first):
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The shell specified with \-\-shell\&.
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\fB\-\-preserve\-environment\fR
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is used, the shell specified by the
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environment variable\&.
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The shell indicated in the
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entry for the target user\&.
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if a shell could not be found by any above method\&.
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If the target user has a restricted shell (i\&.e\&. the shell field of this user\*(Aqs entry in
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/etc/shells), then the
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environment variable won\*(Aqt be taken into account, unless
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\fB\-m\fR, \fB\-p\fR, \fB\-\-preserve\-environment\fR
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Preserve the current environment, except for:
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reset according to the
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\(lq<space><tab><newline>\(rq, if it was set\&.
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If the target user has a restricted shell, this option has no effect (unless
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is called by root)\&.
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Note that the default behavior for the environment is the following:
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environment variables are reset\&.
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is not used, the environment is copied, except for the variables above\&.
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environment variables are copied if they were set\&.
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environment variables are set according to the
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is used, other environment variables might be set by the
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has many compilation options, only some of which may be in use at any particular site\&.
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The following configuration variables in
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change the behavior of this tool:
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\fBCONSOLE\fR (string)
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If defined, either full pathname of a file containing device names (one per line) or a ":" delimited list of device names\&. Root logins will be allowed only upon these devices\&.
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If not defined, root will be allowed on any device\&.
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The device should be specified without the /dev/ prefix\&.
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\fBCONSOLE_GROUPS\fR (string)
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List of groups to add to the user\*(Aqs supplementary groups set when logging in on the console (as determined by the CONSOLE setting)\&. Default is none\&.
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Use with caution \- it is possible for users to gain permanent access to these groups, even when not logged in on the console\&.
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\fBDEFAULT_HOME\fR (boolean)
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Indicate if login is allowed if we can\*(Aqt cd to the home directory\&. Default is no\&.
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\fIyes\fR, the user will login in the root (/) directory if it is not possible to cd to her home directory\&.
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\fBENV_HZ\fR (string)
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If set, it will be used to define the HZ environment variable when a user login\&. The value must be preceded by
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\fIHZ=\fR\&. A common value on Linux is
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\fBENVIRON_FILE\fR (string)
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If this file exists and is readable, login environment will be read from it\&. Every line should be in the form name=value\&.
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Lines starting with a # are treated as comment lines and ignored\&.
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\fBENV_PATH\fR (string)
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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
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\fI/bin:/usr/bin\fR) and can be preceded by
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\fIPATH=\fR\&. The default value is
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\fIPATH=/bin:/usr/bin\fR\&.
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\fBENV_SUPATH\fR (string)
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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
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\fI/sbin:/bin:/usr/sbin:/usr/bin\fR) and can be preceded by
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\fIPATH=\fR\&. The default value is
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\fIPATH=/sbin:/bin:/usr/sbin:/usr/bin\fR\&.
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\fBENV_TZ\fR (string)
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If set, it will be used to define the TZ environment variable when a user login\&. The value can be the name of a timezone preceded by
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\fITZ=CST6CDT\fR), or the full path to the file containing the timezone specification (for example
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If a full path is specified but the file does not exist or cannot be read, the default is to use
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\fBLOGIN_STRING\fR (string)
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The string used for prompting a password\&. The default is to use "Password: ", or a translation of that string\&. If you set this variable, the prompt will not be translated\&.
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If the string contains
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\fI%s\fR, this will be replaced by the user\*(Aqs name\&.
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\fBMAIL_CHECK_ENAB\fR (boolean)
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Enable checking and display of mailbox status upon login\&.
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You should disable it if the shell startup files already check for mail ("mailx \-e" or equivalent)\&.
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\fBMAIL_DIR\fR (string)
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The mail spool directory\&. This is needed to manipulate the mailbox when its corresponding user account is modified or deleted\&. If not specified, a compile\-time default is used\&.
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\fBMAIL_FILE\fR (string)
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Defines the location of the users mail spool files relatively to their home directory\&.
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variables are used by
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to create, move, or delete the user\*(Aqs mail spool\&.
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\fBMAIL_CHECK_ENAB\fR
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\fIyes\fR, they are also used to define the
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environment variable\&.
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\fBQUOTAS_ENAB\fR (boolean)
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Enable setting of resource limits from
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and ulimit, umask, and niceness from the user\*(Aqs passwd gecos field\&.
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\fBSULOG_FILE\fR (string)
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If defined, all su activity is logged to this file\&.
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\fBSU_NAME\fR (string)
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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"\&.
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\fBSU_WHEEL_ONLY\fR (boolean)
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\fIyes\fR, the user must be listed as a member of the first gid 0 group in
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on most Linux systems) to be able to
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to uid 0 accounts\&. If the group doesn\*(Aqt exist or is empty, no one will be able to
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\fBSYSLOG_SU_ENAB\fR (boolean)
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Enable "syslog" logging of
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activity \- in addition to sulog file logging\&.
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\fBUSERGROUPS_ENAB\fR (boolean)
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Enable setting of the umask group bits to be the same as owner bits (examples: 022 \-> 002, 077 \-> 007) for non\-root users, if the uid is the same as gid, and username is the same as the primary group name\&.
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will remove the user\*(Aqs group if it contains no more members, and
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will create by default a group with the name of the user\&.
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User account information\&.
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Secure user account information\&.
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Shadow password suite configuration\&.
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returns the exit value of the command it executed\&.
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If this command was terminated by a signal,
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returns the number of this signal plus 128\&.
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If su has to kill the command (because it was asked to terminate, and the command did not terminate in time),
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Some exit values from
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are independent from the executed command:
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success (\fB\-\-help\fR
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System or authentication failure
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The requested command was not found
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The requested command could not be executed
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man/man1/su.1
