282 lines
7.3 KiB
Groff
282 lines
7.3 KiB
Groff
.\" $OpenBSD: su.1,v 1.38 2022/12/22 19:53:23 kn Exp $
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.\"
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.\" Copyright (c) 1988, 1990 The Regents of the University of California.
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.\" 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 6.12 (Berkeley) 7/29/91
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.\"
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.Dd $Mdocdate: December 22 2022 $
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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 su
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.Bk -words
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.Op Fl fKLlm
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.Op Fl a Ar auth-type
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.Op Fl c Ar login-class
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.Op Fl s Ar login-shell
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.Op Ar login Op Ar shell-argument ...
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.Ek
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.Sh DESCRIPTION
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The
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.Nm
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utility allows a user to run a shell with the user and group ID of another user
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without having to log out and in as that other user.
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All of the real, effective, and saved user and group IDs as well as all
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supplementary group IDs are always set according to the target user.
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If the target
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.Ar login
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name is not specified,
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.Dq root
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is used.
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.Pp
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By default, the shell of the target login is invoked and the
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.Ev SHELL
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and
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.Ev HOME
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environment variables are set according to the target login,
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whereas the current working directory remains unchanged.
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If the target login has a user ID of 0,
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.Ev LOGNAME
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and
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.Ev USER
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are preserved and
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.Ev PATH
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and the
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.Xr umask 2
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value are set according to
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.Xr login.conf 5 ;
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otherwise,
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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 and
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.Ev PATH
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and the
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.Xr umask 2
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value are preserved.
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The
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.Ev TERM
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environment variable is always preserved.
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The rest of the environment remains unmodified by default.
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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
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Same as the
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.Fl l
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option (deprecated).
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.It Fl a Ar auth-type
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Specify an authentication type such as
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.Dq skey
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or
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.Dq radius .
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.It Fl c Ar login-class
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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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.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 executing system or user startup files.
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For other shells, start a regular shell instead of a login shell when
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the
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.Fl l
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option is used.
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Useful to skip reading shell initialization files.
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.It Fl K
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This is shorthand for
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.Dq Nm Fl a Ar passwd ,
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provided for backwards compatibility.
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.It Fl L
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Loop until a correct username and password combination is entered,
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similar to
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.Xr login 1 .
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Note that in this mode target
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.Ar login
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must be specified explicitly, either on the command line or interactively.
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Additionally,
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.Nm
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will prompt for the password even when invoked by root.
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.It Fl l
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Simulate a full login.
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The shell of the target login is invoked and the current working
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directory is changed to the home directory of the target login.
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.Ev HOME ,
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.Ev SHELL ,
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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 default values for the target login.
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.Ev PATH
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and the
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.Xr umask 2
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value are set according to
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.Xr login.conf 5 .
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Except for preserving
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.Ev TERM ,
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the rest of the environment is discarded.
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.It Fl m
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Leave the environment unmodified.
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The login shell of the invoking user is started,
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and the current working directory is not changed.
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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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.It Fl s Ar login-shell
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Specify the path to an alternate login shell.
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You may only override the shell if you're already root.
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This option will override the shell even if the
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.Fl m
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option is specified.
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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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If shell arguments are provided on the command line,
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they are passed to the login shell of the target login.
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This allows it to pass arbitrary commands via the
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.Fl c
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option as understood by most shells.
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Note that
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.Fl c
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usually expects a single argument only; you have to quote it when
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passing multiple words.
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.Pp
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If group 0 (normally
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.Dq wheel )
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has users listed then only those users can
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.Nm
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to
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.Dq root .
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It is not sufficient to change a user's
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.Pa /etc/passwd
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entry to add them to the
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.Dq wheel
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group; they must explicitly be listed in
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.Pa /etc/group .
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If no one is in the
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.Dq wheel
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group, it is ignored, and anyone who knows the root password is permitted to
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.Nm
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to
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.Dq root .
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.Sh ENVIRONMENT
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The following list provides the values of environment variables
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in the new shell that is started by
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.Nm .
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.Bl -tag -width LOGNAME
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.It Ev HOME
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The home directory of the target login, except that it remains unchanged with
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.Fl m .
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.It Ev LOGNAME
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The target login by default, but unchanged if the target login has
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a UID of 0 or if
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.Fl m
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is given.
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.It Ev PATH
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The search path.
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It remains unchanged by default, but is set according to the target login
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if the target login has a UID of 0 or if
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.Fl l
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is given.
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.It Ev PWD
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The current working directory.
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It remains unchanged by default,
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but is set to the home directory of the target login with
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.Fl l .
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.It Ev SHELL
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The new shell that is started.
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It is the shell of the target login by default,
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but the shell of the invoking user with
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.Fl m .
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.It Ev TERM
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The terminal type.
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It is always retained from the invoking process.
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.It Ev USER
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Same as
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.Ev LOGNAME .
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.El
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.Sh EXAMPLES
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Run the command
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.Dq makewhatis
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as user
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.Dq bin .
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You will be asked for bin's password unless your real UID is 0.
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.Pp
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.Dl $ su bin -c makewhatis
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.Pp
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Same as above, but the target command consists of more than a
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single word:
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.Pp
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.Dl $ su bin -c 'makewhatis /usr/local/man'
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.Pp
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Same as above, but the target command is run with the resource
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limits of the login class
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.Dq staff .
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Note that the first
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.Fl c
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option applies to
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.Nm
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while the second is an argument to the shell.
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.Pp
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.Dl $ su -c staff bin -c 'makewhatis /usr/local/man'
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.Pp
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Pretend a login for user
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.Dq foo :
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.Pp
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.Dl $ su -l foo
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.Pp
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Same as above, but use S/Key for authentication:
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.Pp
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.Dl $ su -a skey -l foo
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.Sh SEE ALSO
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.Xr doas 1 ,
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.Xr login 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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.Sh HISTORY
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A
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.Nm
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command first appeared in
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.At v1 .
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.Sh BUGS
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The login name is not optional for root if there are shell arguments.
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