140 lines
3.6 KiB
Groff
140 lines
3.6 KiB
Groff
.\" Title: su
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.\" Author:
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.\" Generator: DocBook XSL Stylesheets v1.70.1 <http://docbook.sf.net/>
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.\" Date: 07/30/2006
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.\" Manual: User Commands
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.\" Source: User Commands
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.\"
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.TH "SU" "1" "07/30/2006" "User Commands" "User Commands"
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.\" disable hyphenation
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.nh
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.\" disable justification (adjust text to left margin only)
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.ad l
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.SH "NAME"
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su \- change user ID or become super\-user
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.SH "SYNOPSIS"
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.HP 3
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\fBsu\fR [\fIoptions\fR] [\fILOGIN\fR]
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.SH "DESCRIPTION"
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.PP
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\fBsu\fR
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is used to become another user during a login session. Invoked without a
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\fBusername\fR,
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\fBsu\fR
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defaults to becoming the super user. The optional argument
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\fB\-\fR
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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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.PP
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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
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\fB\-c\fR
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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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\fI/etc/passwd\fR
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for the target user.
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.PP
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You can use the
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\fB\-\-\fR
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argument to separate
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\fBsu\fR
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options from the arguments supplied to the shell.
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.PP
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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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.PP
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The current environment is passed to the new shell. The value of
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\fB$PATH\fR
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is reset to
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\fI/bin:/usr/bin\fR
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for normal users, or
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\fI/sbin:/bin:/usr/sbin:/usr/bin\fR
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for the super user. This may be changed with the
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\fIENV_PATH\fR
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and
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\fIENV_SUPATH\fR
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definitions in
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\fI/etc/login.defs\fR.
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.PP
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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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.SH "OPTIONS"
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.PP
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The options which apply to the
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\fBsu\fR
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command are:
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.TP 3n
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\fB\-c\fR, \fB\-\-command\fR \fISHELL\fR
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Specify a command that will be invoked by the shell using its
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\fB\-c\fR.
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.TP 3n
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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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.sp
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When
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\fB\-\fR
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is used, it must be specified as the last
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\fBsu\fR
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option. The other forms (\fB\-l\fR
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and
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\fB\-\-login\fR) do not have this restriction.
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.TP 3n
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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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.sp
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The invoked shell is choosen among (higest priority first):
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.RS 3n
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.TP 3n
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\(bu
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The shell specified with \-\-shell
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.TP 3n
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\(bu
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If
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\fB\-\-preserve\-environment\fR
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is used, the shell specified by the
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\fB$SHELL\fR
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environment variable.
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.TP 3n
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\(bu
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The shell indicated in the
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\fI/etc/passwd\fR
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entry for the target user.
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.TP 3n
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\(bu
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\fI/bin/sh\fR
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if a shell could not be found by any above method.
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.RE
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.IP "" 3n
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.sp
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If the target user has a restricted shell (i.e. the shell field of this user's entry in
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\fI/etc/passwd\fR
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is not specified in
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\fI/etc/shell\fR), then the
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\fB\-\-shell\fR
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option or the
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\fB$SHELL\fR
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environment variable won't be taken into account unless
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\fBsu\fR
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is called by the root.
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.TP 3n
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\fB\-m\fR, \fB\-p\fR, \fB\-\-preserve\-environment\fR
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Preserve the current environment.
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.sp
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If the target user has a restricted shell, this option has no effect (unless
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\fBsu\fR
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is called by root).
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.SH "CAVEATS"
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.PP
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This version of
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\fBsu\fR
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has many compilation options, only some of which may be in use at any particular site.
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.SH "FILES"
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.TP 3n
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\fI/etc/passwd\fR
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User account information.
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.TP 3n
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\fI/etc/shadow\fR
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Secure user account information.
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.SH "SEE ALSO"
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.PP
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\fBlogin\fR(1),
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\fBlogin.defs\fR(5),
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\fBsh\fR(1)
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