.\" $Id: su.1,v 1.18 2005/05/19 10:35:00 kloczek Exp $
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.TH SU 1
.SH NAME
su \- change user ID or become super\-user
.SH SYNOPSIS
\fBsu\fR [\fB\-\fR] [\fIusername\fR [\fIargs\fR]]
.SH DESCRIPTION
\fBsu\fR is used to become another user during a login session. Invoked
without a username, \fBsu\fR defaults to becoming the super user. The
optional argument \fB\-\fR may be used to provide an environment similar to
what the user would expect had the user logged in directly.
.PP
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
\fB\-c\fR 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
\fI/etc/passwd\fR for the target user.
.PP
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 abuses of the system.
.PP
The current environment is passed to the new shell. The value of \fB$PATH\fR
\is reset to \fB/bin:/usr/bin\fR for normal users, or
\fB/sbin:/bin:/usr/sbin:/usr/bin\fR for the super user. This may be changed
with the \fBENV_PATH\fR and \fBENV_SUPATH\fR definitions in
\fI/etc/login.defs\fR.
.PP
A subsystem login is indicated by the presense of a "*" as the first
character of the login shell. The given home directory will be used as
the root of a new filesystem which the user is actually logged into.
.SH CAVEATS
This version of \fBsu\fR has many compilation options, only some of which
may be in use at any particular site.
.SH FILES
\fI/etc/passwd\fR	\- user account information
.br
\fI/etc/shadow\fR	\- secure user account information
.SH SEE ALSO
.BR login (1),
.BR sh (1),
.BR login.defs (5),
.BR suauth (5)
.SH AUTHOR
Julianne Frances Haugh <jockgrrl@ix.netcom.com>