NAME

su − become super user or another user

SYNOPSIS

su [ − ] [ username [ arg ... ] ]

DESCRIPTION

su allows one to become another user without logging off.  The default user name is root (super user). 

To use su, the appropriate password must be supplied (unless the invoker is already root).  If the password is correct, su creates a new shell process that has the real and effective user ID, group IDs, and supplementary group list set to those of the specified username.  The new shell will be the shell specified in the shell field of username’s password file entry (see passwd(4)).  If no shell is specified, /usr/bin/sh is used (see sh(1)).  To return to normal user ID privileges, type an EOF character (CTRL-D) to exit the new shell. 

Any additional arguments given on the command line are passed to the new shell.  When using programs such as sh, an arg of the form −c string executes string using the shell and an arg of −r gives the user a restricted shell. 

The following statements are true only if either /usr/bin/sh or NULL is named in the specified user’s password file entry.  If the first argument to su is a ’ - ’ (dash), the environment is passed along unchanged, as if the user actually logged in as the specified user.  Otherwise, the environment is passed along, with the exception of $PATH, which is controlled by PATH and SUPATH in etc/default/su. 

All attempts to become another user using su are logged in the log file /var/adm/sulog (see sulog(4)). 

SECURITY

su uses pam(3) for authentication, account management, and session management.  The PAM configuration policy, listed through /etc/pam.conf, specifies the modules to be used for su.  Here is a partial pam.conf file with entries for the su command using the UNIX authentication, account management, and session management module. 

If there are no entries for the su service, then the entries for the "other" service will be used.  If multiple authentication modules are listed, then the user may be prompted for multiple passwords. 

EXAMPLES

To become user bin while retaining your previously exported environment, execute:

example% su bin

To become user bin but change the environment to what would be expected if bin had originally logged in, execute:

example% su − bin

To execute command with the temporary environment and permissions of user bin, type:

example% su − bin −c "command args"

ENVIRONMENT

If any of the LC_∗ variables ( LC_CTYPE, LC_MESSAGES, LC_TIME, LC_COLLATE, LC_NUMERIC, and LC_MONETARY ) (see environ(5)) are not set in the environment, the operational behavior of su for each corresponding locale category is determined by the value of the LANG environment variable.  If LC_ALL is set, its contents are used to override both the LANG and the other LC_∗ variables.  If none of the above variables are set in the environment, the "C"  (U.S. style) locale determines how su behaves. 

LC_CTYPE Determines how su handles characters. When LC_CTYPE is set to a valid value, su can display and handle text and filenames containing valid characters for that locale.  su can display and handle Extended Unix Code (EUC) characters where any individual character can be 1, 2, or 3 bytes wide.  su can also handle EUC characters of 1, 2, or more column widths. In the "C" locale, only characters from ISO 8859-1 are valid. 

LC_MESSAGES
Determines how diagnostic and informative messages are presented. This includes the language and style of the messages, and the correct form of affirmative and negative responses.  In the "C" locale, the messages are presented in the default form found in the program itself (in most cases, U.S. English).

FILES

$HOME/.profile user’s login commands for sh and ksh

/etc/passwd system’s password file

/etc/profile system-wide sh and ksh login commands

/var/adm/sulog log file

/etc/default/su the default parameters that reside here are:

SULOG: If defined, all attempts to su to another user are logged in the indicated file. 

CONSOLE: If defined, all attempts to su to root are logged on the console. 

PATH: Default path. (/usr/bin:)

SUPATH: Default path for a user invoking su to root.  (/usr/sbin:/usr/bin)

SYSLOG: Determines whether the syslog(3) LOG_AUTH facility should be used to log all su attempts.  LOG_NOTICE messages are generated for su’s to root, LOG_INFO messages are generated for su’s to other users, and LOG_CRIT messages are generated for failed su attempts. 

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

SEE ALSO

csh(1), env(1), ksh(1), login(1), sh(1), syslogd(1M), pam(3), syslog(3), pam.conf(4), passwd(4), profile(4), sulog(4), attributes(5), environ(5), pam_unix(5)

SunOS 5.6  —  Last change: 28 Oct 1996