1SUDO(8) MAINTENANCE COMMANDS SUDO(8)
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6 sudo, sudoedit - execute a command as another user
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9 sudo -K ⎪ -L ⎪ -V ⎪ -h ⎪ -k ⎪ -l ⎪ -v
10 sudo [-HPSb] [-a auth_type] [-c class⎪-] [-p prompt] [-u username⎪#uid]
12 {-e file [...] ⎪ -i ⎪ -s ⎪ command}
13 sudoedit [-S] [-a auth_type] [-p prompt] [-u username⎪#uid] file [...]
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17 sudo allows a permitted user to execute a command as the superuser or
18 another user, as specified in the sudoers file. The real and effective
19 uid and gid are set to match those of the target user as specified in
20 the passwd file and the group vector is initialized based on the group
21 file (unless the -P option was specified). If the invoking user is
22 root or if the target user is the same as the invoking user, no pass‐
23 word is required. Otherwise, sudo requires that users authenticate
24 themselves with a password by default (NOTE: in the default configura‐
25 tion this is the user's password, not the root password). Once a user
26 has been authenticated, a timestamp is updated and the user may then
27 use sudo without a password for a short period of time (5 minutes
28 unless overridden in sudoers).
29 When invoked as sudoedit, the -e option (described below), is implied.
31 sudo determines who is an authorized user by consulting the file
33 /etc/sudoers. By giving sudo the -v flag a user can update the time
34 stamp without running a command. The password prompt itself will also
35 time out if the user's password is not entered within 5 minutes (unless
36 overridden via sudoers).
37 If a user who is not listed in the sudoers file tries to run a command
39 via sudo, mail is sent to the proper authorities, as defined at config‐
40 ure time or in the sudoers file (defaults to root). Note that the mail
41 will not be sent if an unauthorized user tries to run sudo with the -l
42 or -v flags. This allows users to determine for themselves whether or
43 not they are allowed to use sudo.
44 If sudo is run by root and the SUDO_USER environment variable is set,
46 sudo will use this value to determine who the actual user is. This can
47 be used by a user to log commands through sudo even when a root shell
48 has been invoked. It also allows the -e flag to remain useful even
49 when being run via a sudo-run script or program. Note however, that
50 the sudoers lookup is still done for root, not the user specified by
51 SUDO_USER.
52 sudo can log both successful and unsuccessful attempts (as well as
54 errors) to syslog(3), a log file, or both. By default sudo will log
55 via syslog(3) but this is changeable at configure time or via the sudo‐
56 ers file.
57
59 sudo accepts the following command line options:
60 -H The -H (HOME) option sets the HOME environment variable to the
62 homedir of the target user (root by default) as specified in
63 passwd(5). By default, sudo does not modify HOME (see set_home and
64 always_set_home in sudoers(5)).
65 -K The -K (sure kill) option is like -k except that it removes the
67 user's timestamp entirely. Like -k, this option does not require a
68 password.
69 -L The -L (list defaults) option will list out the parameters that may
71 be set in a Defaults line along with a short description for each.
72 This option is useful in conjunction with grep(1).
73 -P The -P (preserve group vector) option causes sudo to preserve the
75 invoking user's group vector unaltered. By default, sudo will ini‐
76 tialize the group vector to the list of groups the target user is
77 in. The real and effective group IDs, however, are still set to
78 match the target user.
79 -S The -S (stdin) option causes sudo to read the password from the
81 standard input instead of the terminal device.
82 -V The -V (version) option causes sudo to print the version number and
84 exit. If the invoking user is already root the -V option will
85 print out a list of the defaults sudo was compiled with as well as
86 the machine's local network addresses.
87 -a The -a (authentication type) option causes sudo to use the speci‐
89 fied authentication type when validating the user, as allowed by
90 /etc/login.conf. The system administrator may specify a list of
91 sudo-specific authentication methods by adding an "auth-sudo" entry
92 in /etc/login.conf. This option is only available on systems that
93 support BSD authentication where sudo has been configured with the
94 --with-bsdauth option.
95 -b The -b (background) option tells sudo to run the given command in
97 the background. Note that if you use the -b option you cannot use
98 shell job control to manipulate the process.
99 -c The -c (class) option causes sudo to run the specified command with
101 resources limited by the specified login class. The class argument
102 can be either a class name as defined in /etc/login.conf, or a sin‐
103 gle '-' character. Specifying a class of - indicates that the com‐
104 mand should be run restricted by the default login capabilities for
105 the user the command is run as. If the class argument specifies an
106 existing user class, the command must be run as root, or the sudo
107 command must be run from a shell that is already root. This option
108 is only available on systems with BSD login classes where sudo has
109 been configured with the --with-logincap option.
110 -e The -e (edit) option indicates that, instead of running a command,
112 the user wishes to edit one or more files. In lieu of a command,
113 the string "sudoedit" is used when consulting the sudoers file. If
114 the user is authorized by sudoers the following steps are taken:
115 1. Temporary copies are made of the files to be edited with
117 the owner set to the invoking user.
118 2. The editor specified by the VISUAL or EDITOR environment
120 variables is run to edit the temporary files. If neither
121 VISUAL nor EDITOR are set, the program listed in the editor
122 sudoers variable is used.
123 3. If they have been modified, the temporary files are copied
125 back to their original location and the temporary versions
126 are removed.
127 If the specified file does not exist, it will be created. Note
129 that unlike most commands run by sudo, the editor is run with the
130 invoking user's environment unmodified. If, for some reason, sudo
131 is unable to update a file with its edited version, the user will
132 receive a warning and the edited copy will remain in a temporary
133 file.
134 -h The -h (help) option causes sudo to print a usage message and exit.
136 -i The -i (simulate initial login) option runs the shell specified in
138 the passwd(5) entry of the user that the command is being run as.
139 The command name argument given to the shell begins with a - to
140 tell the shell to run as a login shell. sudo attempts to change to
141 that user's home directory before running the shell. It also ini‐
142 tializes the environment, leaving TERM unchanged, setting HOME,
143 SHELL, USER, LOGNAME, and PATH, and unsetting all other environment
144 variables. Note that because the shell to use is determined before
145 the sudoers file is parsed, a runas_default setting in sudoers will
146 specify the user to run the shell as but will not affect which
147 shell is actually run.
148 -k The -k (kill) option to sudo invalidates the user's timestamp by
150 setting the time on it to the epoch. The next time sudo is run a
151 password will be required. This option does not require a password
152 and was added to allow a user to revoke sudo permissions from a
153 .logout file.
154 -l The -l (list) option will list out the allowed (and forbidden) com‐
156 mands for the user on the current host.
157 -p The -p (prompt) option allows you to override the default password
159 prompt and use a custom one. The following percent (`%') escapes
160 are supported:
161 %u expanded to the invoking user's login name
163 %U expanded to the login name of the user the command will be
165 run as (defaults to root)
166 %h expanded to the local hostname without the domain name
168 %H expanded to the local hostname including the domain name
170 (on if the machine's hostname is fully qualified or the
171 fqdn sudoers option is set)
172 %% two consecutive % characters are collapsed into a single %
174 character
175 -s The -s (shell) option runs the shell specified by the SHELL envi‐
177 ronment variable if it is set or the shell as specified in
178 passwd(5).
179 -u The -u (user) option causes sudo to run the specified command as a
181 user other than root. To specify a uid instead of a username, use
182 #uid. Note that if the targetpw Defaults option is set (see sudo‐
183 ers(5)) it is not possible to run commands with a uid not listed in
184 the password database.
185 -v If given the -v (validate) option, sudo will update the user's
187 timestamp, prompting for the user's password if necessary. This
188 extends the sudo timeout for another 5 minutes (or whatever the
189 timeout is set to in sudoers) but does not run a command.
190 -- The -- flag indicates that sudo should stop processing command line
192 arguments. It is most useful in conjunction with the -s flag.
193
195 Upon successful execution of a program, the return value from sudo will
196 simply be the return value of the program that was executed.
197 Otherwise, sudo quits with an exit value of 1 if there is a configura‐
199 tion/permission problem or if sudo cannot execute the given command.
200 In the latter case the error string is printed to stderr. If sudo can‐
201 not stat(2) one or more entries in the user's PATH an error is printed
202 on stderr. (If the directory does not exist or if it is not really a
203 directory, the entry is ignored and no error is printed.) This should
204 not happen under normal circumstances. The most common reason for
205 stat(2) to return "permission denied" is if you are running an auto‐
206 mounter and one of the directories in your PATH is on a machine that is
207 currently unreachable.
208
210 sudo tries to be safe when executing external commands. Variables that
211 control how dynamic loading and binding is done can be used to subvert
212 the program that sudo runs. To combat this the LD_*, _RLD_*,
213 SHLIB_PATH (HP-UX only), and LIBPATH (AIX only) environment variables
214 are removed from the environment passed on to all commands executed.
215 sudo will also remove the IFS, CDPATH, ENV, BASH_ENV, KRB_CONF, KRB‐
216 CONFDIR, KRBTKFILE, KRB5_CONFIG, LOCALDOMAIN, RES_OPTIONS, HOSTALIASES,
217 NLSPATH, PATH_LOCALE, TERMINFO, TERMINFO_DIRS and TERMPATH variables as
218 they too can pose a threat. If the TERMCAP variable is set and is a
219 pathname, it too is ignored. Additionally, if the LC_* or LANGUAGE
220 variables contain the / or % characters, they are ignored. Environment
221 variables with a value beginning with () are also removed as they could
222 be interpreted as bash functions. If sudo has been compiled with
223 SecurID support, the VAR_ACE, USR_ACE and DLC_ACE variables are cleared
224 as well. The list of environment variables that sudo clears is con‐
225 tained in the output of sudo -V when run as root.
226 To prevent command spoofing, sudo checks "." and "" (both denoting cur‐
228 rent directory) last when searching for a command in the user's PATH
229 (if one or both are in the PATH). Note, however, that the actual PATH
230 environment variable is not modified and is passed unchanged to the
231 program that sudo executes.
232 For security reasons, if your OS supports shared libraries and does not
234 disable user-defined library search paths for setuid programs (most
235 do), you should either use a linker option that disables this behavior
236 or link sudo statically.
237 sudo will check the ownership of its timestamp directory (/var/run/sudo
239 by default) and ignore the directory's contents if it is not owned by
240 root and only writable by root. On systems that allow non-root users
241 to give away files via chown(2), if the timestamp directory is located
242 in a directory writable by anyone (e.g.: /tmp), it is possible for a
243 user to create the timestamp directory before sudo is run. However,
244 because sudo checks the ownership and mode of the directory and its
245 contents, the only damage that can be done is to "hide" files by
246 putting them in the timestamp dir. This is unlikely to happen since
247 once the timestamp dir is owned by root and inaccessible by any other
248 user the user placing files there would be unable to get them back out.
249 To get around this issue you can use a directory that is not world-
250 writable for the timestamps (/var/adm/sudo for instance) or create
251 /var/run/sudo with the appropriate owner (root) and permissions (0700)
252 in the system startup files.
253 sudo will not honor timestamps set far in the future. Timestamps with
255 a date greater than current_time + 2 * TIMEOUT will be ignored and sudo
256 will log and complain. This is done to keep a user from creating
257 his/her own timestamp with a bogus date on systems that allow users to
258 give away files.
259 Please note that sudo will only log the command it explicitly runs. If
261 a user runs a command such as sudo su or sudo sh, subsequent commands
262 run from that shell will not be logged, nor will sudo's access control
263 affect them. The same is true for commands that offer shell escapes
264 (including most editors). Because of this, care must be taken when
265 giving users access to commands via sudo to verify that the command
266 does not inadvertently give the user an effective root shell.
267
269 sudo utilizes the following environment variables:
270 EDITOR Default editor to use in -e (sudoedit) mode if
272 VISUAL is not set
273 HOME In -s or -H mode (or if sudo was configured with
275 the --enable-shell-sets-home option), set to
276 homedir of the target user
277 PATH Set to a sane value if sudo was configured with
279 the --with-secure-path option
280 SHELL Used to determine shell to run with -s option
282 SUDO_PROMPT Used as the default password prompt
284 SUDO_COMMAND Set to the command run by sudo
286 SUDO_USER Set to the login of the user who invoked sudo
288 SUDO_UID Set to the uid of the user who invoked sudo
290 SUDO_GID Set to the gid of the user who invoked sudo
292 SUDO_PS1 If set, PS1 will be set to its value
294 USER Set to the target user (root unless the -u option
296 is specified)
297 VISUAL Default editor to use in -e (sudoedit) mode
299
301 /etc/sudoers List of who can run what
302 /var/run/sudo Directory containing timestamps
303
305 Note: the following examples assume suitable sudoers(5) entries.
306 To get a file listing of an unreadable directory:
308 $ sudo ls /usr/local/protected
310 To list the home directory of user yazza on a machine where the file
312 system holding ~yazza is not exported as root:
313 $ sudo -u yazza ls ~yazza
315 To edit the index.html file as user www:
317 $ sudo -u www vi ~www/htdocs/index.html
319 To shutdown a machine:
321 $ sudo shutdown -r +15 "quick reboot"
323 To make a usage listing of the directories in the /home partition.
325 Note that this runs the commands in a sub-shell to make the cd and file
326 redirection work.
327 $ sudo sh -c "cd /home ; du -s * ⎪ sort -rn > USAGE"
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331 grep(1), su(1), stat(2), login_cap(3), sudoers(5), passwd(5), visudo(8)
332
334 Many people have worked on sudo over the years; this version consists
335 of code written primarily by:
336 Todd Miller
338 Chris Jepeway
339 See the HISTORY file in the sudo distribution or visit
341 http://www.sudo.ws/sudo/history.html for a short history of sudo.
342
344 There is no easy way to prevent a user from gaining a root shell if
345 that user is allowed to run arbitrary commands via sudo. Also, many
346 programs (such as editors) allow the user to run commands via shell
347 escapes, thus avoiding sudo's checks. However, on most systems it is
348 possible to prevent shell escapes with sudo's noexec functionality.
349 See the sudoers(5) manual for details.
350 It is not meaningful to run the cd command directly via sudo, e.g.
352 $ sudo cd /usr/local/protected
354 since when whe command exits the parent process (your shell) will still
356 be the same. Please see the EXAMPLES section for more information.
357 If users have sudo ALL there is nothing to prevent them from creating
359 their own program that gives them a root shell regardless of any '!'
360 elements in the user specification.
361 Running shell scripts via sudo can expose the same kernel bugs that
363 make setuid shell scripts unsafe on some operating systems (if your OS
364 has a /dev/fd/ directory, setuid shell scripts are generally safe).
365
367 If you feel you have found a bug in sudo, please submit a bug report at
368 http://www.sudo.ws/sudo/bugs/
369
371 Commercial support is available for sudo, see
372 http://www.sudo.ws/sudo/support.html for details.
373 Limited free support is available via the sudo-users mailing list, see
375 http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search
376 the archives.
377
379 Sudo is provided ``AS IS'' and any express or implied warranties,
380 including, but not limited to, the implied warranties of merchantabil‐
381 ity and fitness for a particular purpose are disclaimed. See the
382 LICENSE file distributed with sudo or
383 http://www.sudo.ws/sudo/license.html for complete details.
3841.6.8p12 June 20, 2005 SUDO(8)