399 lines
8.6 KiB
Groff
399 lines
8.6 KiB
Groff
.\" Copyright (c) 1988, 1990, 1993, 1994
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" from: @(#)su.1 8.2 (Berkeley) 4/18/94
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.\" $NetBSD: su.1,v 1.55 2023/03/24 14:34:17 kre Exp $
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.\"
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.Dd September 1, 2019
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.Dt SU 1
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.Os
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.Sh NAME
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.Nm su
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.Nd substitute user identity
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.Sh SYNOPSIS
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.Nm
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.Op Fl dfKlm
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.Op Fl c Ar login-class
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.Oo
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.Ar login Ns Op : Ns Ar group
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.Op Ar "shell arguments"
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.Oc
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.Nm
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.Op Fl dfKlm
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.Op Fl c Ar login-class
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.Oo : Ns Ar group
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.Op Ar "shell arguments"
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.Oc
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.Sh DESCRIPTION
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.Nm
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allows one user to become another user
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.Ar login
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without logging out and in as
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the new user.
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If a
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.Ar group
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is specified and
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.Ar login
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is a member of
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.Ar group ,
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then the group is changed to
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.Ar group
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rather than to
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.Ar login Ns 's
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primary group.
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If
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.Ar login
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is omitted and
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.Ar group
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is provided (form two above), then
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.Ar login
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is assumed to be the current username.
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If neither
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.Ar login
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nor
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.Ar group
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is provided,
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.Dq root
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is used for
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.Ar login .
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.Pp
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When executed by a user, the
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.Ar login
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user's password is requested.
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When using Kerberos, the password for
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.Ar login
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(or for
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.Dq Ar login Ns .root ,
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if no login is provided) is requested, and
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.Nm
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switches to that user and group ID after obtaining a Kerberos ticket
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granting ticket.
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A shell is then executed, and any additional
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.Ar "shell arguments"
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after the login name are passed to the shell.
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.Nm
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will resort to the local password file to find the password for
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.Ar login
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if there is a Kerberos error.
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If
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.Nm
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is executed by root, no password is requested and a shell
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with the appropriate user ID is executed; no additional Kerberos tickets
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are obtained.
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.Pp
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Alternatively, if the user enters the password "s/key", authentication
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will use the S/Key one-time password system as described in
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.Xr skey 1 .
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S/Key is a Trademark of Bellcore.
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.Pp
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By default, the environment is unmodified with the exception of
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.Ev LOGNAME ,
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.Ev USER ,
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.Ev HOME ,
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.Ev SHELL ,
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and
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.Ev SU_FROM .
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.Ev HOME
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and
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.Ev SHELL
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are set to the target login's default values.
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.Ev LOGNAME
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and
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.Ev USER
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are set to the target login, unless the target login has a user ID of 0,
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in which case they are unmodified.
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.Ev SU_FROM
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is set to the caller's login.
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The invoked shell is the target login's.
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With the exception of
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.Ev SU_FROM
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this is the traditional behavior of
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.Nm .
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.Pp
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The options are as follows:
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.Bl -tag -width Ds
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.It Fl c
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Specify a login class.
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You may only override the default class if you're already root.
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See
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.Xr login.conf 5
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for details.
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.It Fl d
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Same as
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.Fl l ,
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but does not change the current directory.
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.It Fl f
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If the invoked shell is
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.Xr csh 1 ,
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this option prevents it from reading the
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.Dq Pa .cshrc
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file.
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If the invoked shell is
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.Xr sh 1 ,
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or
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.Xr ksh 1 ,
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this option unsets
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.Ev ENV ,
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thus preventing the shell from executing the startup file pointed to by
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this variable.
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.It Fl K
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Do not attempt to use Kerberos to authenticate the user.
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.It Fl l
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Simulate a full login.
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The environment is discarded except for
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.Ev HOME ,
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.Ev SHELL ,
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.Ev PATH ,
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.Ev TERM ,
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.Ev LOGNAME ,
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.Ev USER ,
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and
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.Ev SU_FROM .
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.Ev HOME ,
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.Ev SHELL ,
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and
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.Ev SU_FROM
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are modified as above.
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.Ev LOGNAME
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and
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.Ev USER
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are set to the target login.
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.Ev PATH
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is set to the path specified in the
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.Pa /etc/login.conf
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file (or to the default of
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.Dq Pa /usr/bin:/bin:/usr/pkg/bin:/usr/local/bin
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).
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.Ev TERM
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is imported from your current environment.
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The invoked shell is the target login's, and
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.Nm
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will change directory to the target login's home directory.
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The
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.Xr utmp 5 ,
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.Xr wtmp 5 ,
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and
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.Xr lastlog 5
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databases are not updated.
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.It Fl
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Same as
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.Fl l .
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.It Fl m
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Leave the environment unmodified.
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The invoked shell is your login shell, and no directory changes are made.
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As a security precaution, if the target user's shell is a non-standard
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shell (as defined by
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.Xr getusershell 3 )
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and the caller's real uid is
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non-zero,
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.Nm
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will fail.
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.El
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.Pp
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The
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.Fl l
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and
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.Fl m
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options are mutually exclusive; the last one specified
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overrides any previous ones.
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.Pp
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Only users in group
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.Dq wheel
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(normally gid 0),
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as listed in
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.Pa /etc/group ,
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can
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.Nm
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to
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.Dq root ,
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unless group wheel does not exist or has no members.
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(If you do not want anybody to be able to
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.Nm
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to
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.Dq root ,
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make
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.Dq root
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the only member of group
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.Dq wheel ,
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which is the default.)
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.Pp
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For sites with very large user populations, group
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.Dq wheel
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can contain the names of other groups that will be considered authorized
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to
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.Nm
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to
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.Dq root .
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.Pp
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By default (unless the prompt is reset by a startup file) the super-user
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prompt is set to
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.Dq Sy \&#
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to remind one of its awesome power.
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.Sh CUSTOMIZATION
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.Bl -tag -width ""
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.It Changing required group
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For the
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.Xr pam 8
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version of
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.Nm
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the name of the required group can be changed by setting
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.Ar gname
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in
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.Xr pam.conf 5 :
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.Bd -literal
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auth requisite pam_group.so no_warn group=gname root_only fail_safe
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.Ed
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.Pp
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For the non
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.Xr pam 8
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version of
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.Nm
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the same can be achieved by compiling with
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.Dv SU_GROUP
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set to the desired group name.
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.It Supplying own password
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.Nm
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can be configured so that users in a particular group can supply their
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own password to become
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.Dq root .
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For the
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.Xr pam 8
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version of
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.Nm
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this can be done by adding a line to
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.Xr pam.conf 5
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such as:
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.Bd -literal
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auth sufficient pam_group.so no_warn group=gname root_only authenticate
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.Ed
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.Pp
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where
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.Ar gname
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is the name of the desired group.
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For the non
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.Xr pam 8
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version of
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.Nm
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the same can be achieved by compiling with
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.Dv SU_ROOTAUTH
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set to the desired group name.
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.It Indirect groups
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This option is not available with the
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.Xr pam 8
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version of
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.Nm .
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For the non
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.Xr pam 8
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version of
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.Nm ,
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if
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.Dv SU_INDIRECT_GROUP
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is defined, the
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.Ar SU_GROUP
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and
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.Ar SU_ROOTAUTH
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groups are treated as indirect groups.
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The group members of those two groups are treated as groups themselves.
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.El
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.Sh ENVIRONMENT
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Environment variables used by
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.Nm :
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.Bl -tag -width "HOME"
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.It Ev HOME
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Default home directory of real user ID unless modified as
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specified above.
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.It Ev LOGNAME
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The user ID is always the effective ID (the target user ID) after an
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.Nm
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unless the user ID is 0 (root).
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.It Ev PATH
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Default search path of real user ID unless modified as specified above.
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.It Ev TERM
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Provides terminal type which may be retained for the substituted
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user ID.
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.It Ev USER
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The user ID is always the effective ID (the target user ID) after an
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.Nm
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unless the user ID is 0 (root).
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.El
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.Sh EXIT STATUS
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.Nm
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returns the exit status of the executed subshell, or 1 if any error
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occurred while switching privileges.
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.Sh EXAMPLES
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To become user username and use the same environment as in original shell, execute:
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.Bd -literal -offset indent
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su username
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.Ed
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.Pp
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To become user username and use environment as if full login would be performed,
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execute:
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.Bd -literal -offset indent
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su -l username
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.Ed
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.Pp
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When a
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.Fl c
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option is included
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.Em after
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the
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.Ar login
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name it is not a
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.Nm
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option, because any arguments after the
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.Ar login
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are passed to the shell.
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(See
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.Xr csh 1 ,
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.Xr ksh 1
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or
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.Xr sh 1
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for details.)
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To execute arbitrary command with privileges of user
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.Em username ,
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execute:
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.Bd -literal -offset indent
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su username -c "command args"
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.Ed
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.Sh SEE ALSO
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.Xr csh 1 ,
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.Xr kinit 1 ,
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.Xr login 1 ,
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.Xr sh 1 ,
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.Xr skey 1 ,
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.Xr setusercontext 3 ,
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.Xr group 5 ,
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.Xr login.conf 5 ,
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.Xr passwd 5 ,
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.Xr environ 7 ,
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.Xr kerberos 8
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.Sh HISTORY
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An
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.Nm
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utility appeared in
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.At v1
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