1.\" Copyright (c) 1988, 1990, 1993, 1994 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)su.1 8.2 (Berkeley) 4/18/94 33.\" $FreeBSD$ 34.\" 35.Dd September 13, 2006 36.Dt SU 1 37.Os 38.Sh NAME 39.Nm su 40.Nd substitute user identity 41.Sh SYNOPSIS 42.Nm 43.Op Fl 44.Op Fl flms 45.Op Fl c Ar class 46.Op Ar login Op Ar args 47.Sh DESCRIPTION 48The 49.Nm 50utility requests appropriate user credentials via PAM 51and switches to that user ID 52(the default user is the superuser). 53A shell is then executed. 54.Pp 55PAM is used to set the policy 56.Xr su 1 57will use. 58In particular, by default only users in the 59.Dq Li wheel 60group can switch to UID 0 61.Pq Dq Li root . 62This group requirement may be changed by modifying the 63.Dq Li pam_group 64section of 65.Pa /etc/pam.d/su . 66See 67.Xr pam_group 8 68for details on how to modify this setting. 69.Pp 70By default, the environment is unmodified with the exception of 71.Ev USER , 72.Ev HOME , 73and 74.Ev SHELL . 75.Ev HOME 76and 77.Ev SHELL 78are set to the target login's default values. 79.Ev USER 80is set to the target login, unless the target login has a user ID of 0, 81in which case it is unmodified. 82The invoked shell is the one belonging to the target login. 83This is the traditional behavior of 84.Nm . 85Resource limits and session priority applicable to the original user's 86login class (see 87.Xr login.conf 5 ) 88are also normally retained unless the target login has a user ID of 0. 89.Pp 90The options are as follows: 91.Bl -tag -width Ds 92.It Fl f 93If the invoked shell is 94.Xr csh 1 , 95this option prevents it from reading the 96.Dq Pa .cshrc 97file. 98.It Fl l 99Simulate a full login. 100The environment is discarded except for 101.Ev HOME , 102.Ev SHELL , 103.Ev PATH , 104.Ev TERM , 105and 106.Ev USER . 107.Ev HOME 108and 109.Ev SHELL 110are modified as above. 111.Ev USER 112is set to the target login. 113.Ev PATH 114is set to 115.Dq Pa /bin:/usr/bin . 116.Ev TERM 117is imported from your current environment. 118Environment variables may be set or overridden from the login class 119capabilities database according to the class of the target login. 120The invoked shell is the target login's, and 121.Nm 122will change directory to the target login's home directory. 123Resource limits and session priority are modified to that for the 124target account's login class. 125.It Fl 126(no letter) The same as 127.Fl l . 128.It Fl m 129Leave the environment unmodified. 130The invoked shell is your login shell, and no directory changes are made. 131As a security precaution, if the target user's shell is a non-standard 132shell (as defined by 133.Xr getusershell 3 ) 134and the caller's real uid is 135non-zero, 136.Nm 137will fail. 138.It Fl s 139Set the MAC label to the user's default label as part of the user 140credential setup. 141Setting the MAC label may fail if the MAC label of the invoking process 142is not sufficient to transition to the user's default MAC label. 143If the label cannot be set, 144.Nm 145will fail. 146.It Fl c Ar class 147Use the settings of the specified login class. 148Only allowed for the super-user. 149.El 150.Pp 151The 152.Fl l 153(or 154.Fl ) 155and 156.Fl m 157options are mutually exclusive; the last one specified 158overrides any previous ones. 159.Pp 160If the optional 161.Ar args 162are provided on the command line, they are passed to the login shell of 163the target login. 164Note that all command line arguments before the target login name are 165processed by 166.Nm 167itself, everything after the target login name gets passed to the login 168shell. 169.Pp 170By default (unless the prompt is reset by a startup file) the super-user 171prompt is set to 172.Dq Sy \&# 173to remind one of its awesome power. 174.Sh ENVIRONMENT 175Environment variables used by 176.Nm : 177.Bl -tag -width HOME 178.It Ev HOME 179Default home directory of real user ID unless modified as 180specified above. 181.It Ev PATH 182Default search path of real user ID unless modified as specified above. 183.It Ev TERM 184Provides terminal type which may be retained for the substituted 185user ID. 186.It Ev USER 187The user ID is always the effective ID (the target user ID) after an 188.Nm 189unless the user ID is 0 (root). 190.El 191.Sh FILES 192.Bl -tag -width ".Pa /etc/pam.d/su" -compact 193.It Pa /etc/pam.d/su 194PAM configuration for 195.Nm . 196.El 197.Sh EXAMPLES 198.Bl -tag -width 5n -compact 199.It Li "su man -c catman" 200Runs the command 201.Li catman 202as user 203.Li man . 204You will be asked for man's password unless your real UID is 0. 205.It Li "su man -c 'catman /usr/share/man /usr/local/man'" 206Same as above, but the target command consists of more than a 207single word and hence is quoted for use with the 208.Fl c 209option being passed to the shell. 210(Most shells expect the argument to 211.Fl c 212to be a single word). 213.It Li "su -c staff man -c 'catman /usr/share/man /usr/local/man'" 214Same as above, but the target command is run with the resource limits of 215the login class 216.Dq staff . 217Note: in this example, the first 218.Fl c 219option applies to 220.Nm 221while the second is an argument to the shell being invoked. 222.It Li "su -l foo" 223Simulate a login for user foo. 224.It Li "su - foo" 225Same as above. 226.It Li "su -" 227Simulate a login for root. 228.El 229.Sh SEE ALSO 230.Xr csh 1 , 231.Xr sh 1 , 232.Xr group 5 , 233.Xr login.conf 5 , 234.Xr passwd 5 , 235.Xr environ 7 , 236.Xr pam_group 8 237.Sh HISTORY 238A 239.Nm 240command appeared in 241.At v1 . 242