sudo -h | -K | -k | -V
sudo -v [-AknS] [-g group] [-h host] [-p prompt] [-u user]
sudo -l [-AknS] [-g group] [-h host] [-p prompt] [-U user] [-u user]
sudo [-AbEHnPS] [-C num] [-g group] [-h host] [-p prompt] [-r role]
[-t type] [-u user] [VAR=value] [-i | -s] [command]
sudoedit [-AknS] [-C num] [-g group] [-h host] [-p prompt] [-u user] file
sudo allows a permitted user to execute a command as the superuser or
another user, as specified by the security policy.
sudo supports a plugin architecture for security policies and input/out-
put logging. Third parties can develop and distribute their own policy
and I/O logging plugins to work seamlessly with the sudo front end. The
default security policy is sudoers, which is configured via the file
/etc/sudoers, or via LDAP. See the Plugins section for more information.
The security policy determines what privileges, if any, a user has to run
sudo. The policy may require that users authenticate themselves with a
password or another authentication mechanism. If authentication is
required, sudo will exit if the user's password is not entered within a
configurable time limit. This limit is policy-specific; the default
password prompt timeout for the sudoers security policy is unlimited.
Security policies may support credential caching to allow the user to run
sudo again for a period of time without requiring authentication. The
sudoers policy caches credentials for 15 minutes, unless overridden in
sudoers(5). By running sudo with the -v option, a user can update the
cached credentials without running a command.
When invoked as sudoedit, the -e option (described below), is implied.
Security policies may log successful and failed attempts to use sudo. If
an I/O plugin is configured, the running command's input and output may
be logged as well.
The options are as follows:
Normally, if sudo requires a password, it will read it from
the user's terminal. If the -A (askpass) option is speci-
fied, a (possibly graphical) helper program is executed to
read the user's password and output the password to the stan-
dard output. If the SUDO_ASKPASS environment variable is
set, it specifies the path to the helper program. Otherwise,
if sudo.conf(5) contains a line specifying the askpass pro-
gram, that value will be used. For example:
# Path to askpass helper program
Path askpass /usr/X11R6/bin/ssh-askpass
If no askpass program is available, sudo will exit with an
descriptors other than standard input, standard output and
standard error when executing a command. The security policy
may restrict the user's ability to use this option. The
sudoers policy only permits use of the -C option when the
administrator has enabled the closefrom_override option.
Indicates to the security policy that the user wishes to pre-
serve their existing environment variables. The security
policy may return an error if the user does not have permis-
sion to preserve the environment.
-e, --edit Edit one or more files instead of running a command. In lieu
of a path name, the string "sudoedit" is used when consulting
the security policy. If the user is authorized by the pol-
icy, the following steps are taken:
1. Temporary copies are made of the files to be edited with
the owner set to the invoking user.
2. The editor specified by the policy is run to edit the
temporary files. The sudoers policy uses the
SUDO_EDITOR, VISUAL and EDITOR environment variables (in
that order). If none of SUDO_EDITOR, VISUAL or EDITOR
are set, the first program listed in the editor
sudoers(5) option is used.
3. If they have been modified, the temporary files are
copied back to their original location and the temporary
versions are removed.
If the specified file does not exist, it will be created.
Note that unlike most commands run by sudo, the editor is run
with the invoking user's environment unmodified. If, for
some reason, sudo is unable to update a file with its edited
version, the user will receive a warning and the edited copy
will remain in a temporary file.
-g group, --group=group
Run the command with the primary group set to group instead
of the primary group specified by the target user's password
database entry. The group may be either a group name or a
numeric group ID (GID) prefixed with the '#' character (e.g.
#0 for GID 0). When running a command as a GID, many shells
require that the '#' be escaped with a backslash ('\'). If
no -u option is specified, the command will be run as the
invoking user. In either case, the primary group will be set
Request that the security policy set the HOME environment
variable to the home directory specified by the target user's
password database entry. Depending on the policy, this may
be the default behavior.
base entry as a login shell. This means that login-specific
resource files such as .profile or .login will be read by the
shell. If a command is specified, it is passed to the shell
for execution via the shell's -c option. If no command is
specified, an interactive shell is executed. sudo attempts
to change to that user's home directory before running the
shell. The command is run with an environment similar to the
one a user would receive at log in. The Command Environment
section in the sudoers(5) manual documents how the -i option
affects the environment in which a command is run when the
sudoers policy is in use.
Similar to the -k option, except that it removes the user's
cached credentials entirely and may not be used in conjunc-
tion with a command or other option. This option does not
require a password. Not all security policies support cre-
When used without a command, invalidates the user's cached
credentials. In other words, the next time sudo is run a
password will be required. This option does not require a
password and was added to allow a user to revoke sudo permis-
sions from a .logout file.
When used in conjunction with a command or an option that may
require a password, this option will cause sudo to ignore the
user's cached credentials. As a result, sudo will prompt for
a password (if one is required by the security policy) and
will not update the user's cached credentials.
Not all security policies support credential caching.
-l, --list If no command is specified, list the allowed (and forbidden)
commands for the invoking user (or the user specified by the
-U option) on the current host. A longer list format is used
if this option is specified multiple times and the security
policy supports a verbose output format.
If a command is specified and is permitted by the security
policy, the fully-qualified path to the command is displayed
along with any command line arguments. If command is speci-
fied but not allowed, sudo will exit with a status value of
Avoid prompting the user for input of any kind. If a pass-
word is required for the command to run, sudo will display an
error message and exit.
Preserve the invoking user's group vector unaltered. By
default, the sudoers policy will initialize the group vector
%h expanded to the local host name without the domain name
%p expanded to the name of the user whose password is being
requested (respects the rootpw, targetpw, and runaspw
flags in sudoers(5))
%U expanded to the login name of the user the command will
be run as (defaults to root unless the -u option is also
%u expanded to the invoking user's login name
%% two consecutive '%' characters are collapsed into a sin-
gle '%' character
The custom prompt will override the system password prompt on
systems that support PAM unless the passprompt_override flag
is disabled in sudoers.
-r role, --role=role
Run the command with an SELinux security context that
includes the specified role.
Write the prompt to the standard error and read the password
from the standard input instead of using the terminal device.
The password must be followed by a newline character.
Run the shell specified by the SHELL environment variable if
it is set or the shell specified by the invoking user's pass-
word database entry. If a command is specified, it is passed
to the shell for execution via the shell's -c option. If no
command is specified, an interactive shell is executed.
-t type, --type=type
Run the command with an SELinux security context that
includes the specified type. If no type is specified, the
default type is derived from the role.
-U user, --other-user=user
Used in conjunction with the -l option to list the privileges
for user instead of for the invoking user. The security pol-
icy may restrict listing other users' privileges. The
sudoers policy only allows root or a user with the ALL privi-
lege on the current host to use this option.
-u user, --user=user
Run the command as a user other than the default target user
(usually root ). The user may be either a user name or a
numeric user ID (UID) prefixed with the '#' character (e.g.
#0 for UID 0). When running commands as a UID, many shells
require that the '#' be escaped with a backslash ('\'). Some
Update the user's cached credentials, authenticating the user
if necessary. For the sudoers plugin, this extends the sudo
timeout for another 15 minutes by default, but does not run a
command. Not all security policies support cached creden-
-- The -- option indicates that sudo should stop processing com-
mand line arguments.
Environment variables to be set for the command may also be passed on the
command line in the form of VAR=value, e.g.
LD_LIBRARY_PATH=/usr/local/pkg/lib. Variables passed on the command line
are subject to restrictions imposed by the security policy plugin. The
sudoers policy subjects variables passed on the command line to the same
restrictions as normal environment variables with one important excep-
tion. If the setenv option is set in sudoers, the command to be run has
the SETENV tag set or the command matched is ALL, the user may set vari-
ables that would otherwise be forbidden. See sudoers(5) for more infor-
When sudo executes a command, the security policy specifies the execution
environment for the command. Typically, the real and effective user and
group and IDs are set to match those of the target user, as specified in
the password database, and the group vector is initialized based on the
group database (unless the -P option was specified).
The following parameters may be specified by security policy:
o real and effective user ID
o real and effective group ID
o supplementary group IDs
o the environment list
o current working directory
o file creation mode mask (umask)
o SELinux role and type
o scheduling priority (aka nice value)
When sudo runs a command, it calls fork(2), sets up the execution envi-
ronment as described above, and calls the execve system call in the child
process. The main sudo process waits until the command has completed,
then passes the command's exit status to the security policy's close
function and exits. If an I/O logging plugin is configured or if the
security policy explicitly requests it, a new pseudo-terminal (``pty'')
is created and a second sudo process is used to relay job control signals
When the command is run as a child of the sudo process, sudo will relay
signals it receives to the command. Unless the command is being run in a
new pty, the SIGHUP, SIGINT and SIGQUIT signals are not relayed unless
they are sent by a user process, not the kernel. Otherwise, the command
would receive SIGINT twice every time the user entered control-C. Some
signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not
be relayed to the command. As a general rule, SIGTSTP should be used
instead of SIGSTOP when you wish to suspend a command being run by sudo.
As a special case, sudo will not relay signals that were sent by the com-
mand it is running. This prevents the command from accidentally killing
itself. On some systems, the reboot(8) command sends SIGTERM to all non-
system processes other than itself before rebooting the system. This
prevents sudo from relaying the SIGTERM signal it received back to
reboot(8), which might then exit before the system was actually rebooted,
leaving it in a half-dead state similar to single user mode. Note, how-
ever, that this check only applies to the command run by sudo and not any
other processes that the command may create. As a result, running a
script that calls reboot(8) or shutdown(8) via sudo may cause the system
to end up in this undefined state unless the reboot(8) or shutdown(8) are
run using the exec() family of functions instead of system() (which
interposes a shell between the command and the calling process).
If no I/O logging plugins are loaded and the policy plugin has not
defined a close() function, set a command timeout or required that the
command be run in a new pty, sudo may execute the command directly
instead of running it as a child process.
Plugins may be specified via Plugin directives in the sudo.conf(5) file.
They may be loaded as dynamic shared objects (on systems that support
them), or compiled directly into the sudo binary. If no sudo.conf(5)
file is present, or it contains no Plugin lines, sudo will use the tradi-
tional sudoers security policy and I/O logging. See the sudo.conf(5)
manual for details of the /etc/sudo.conf file and the sudo_plugin(8) man-
ual for more information about the sudo plugin architecture.
Upon successful execution of a program, the exit status from sudo will
simply be the exit status of the program that was executed.
Otherwise, sudo exits with a value of 1 if there is a configuration/per-
mission problem or if sudo cannot execute the given command. In the lat-
ter case the error string is printed to the standard error. If sudo can-
not stat(2) one or more entries in the user's PATH, an error is printed
on stderr. (If the directory does not exist or if it is not really a
directory, the entry is ignored and no error is printed.) This should
not happen under normal circumstances. The most common reason for
stat(2) to return ``permission denied'' is if you are running an auto-
mounter and one of the directories in your PATH is on a machine that is
sudo tries to be safe when executing external commands.
input and/or output logged, but there will not be traditional logs for
those commands. Because of this, care must be taken when giving users
access to commands via sudo to verify that the command does not inadver-
tently give the user an effective root shell. For more information,
please see the PREVENTING SHELL ESCAPES section in sudoers(5).
To prevent the disclosure of potentially sensitive information, sudo dis-
ables core dumps by default while it is executing (they are re-enabled
for the command that is run). To aid in debugging sudo crashes, you may
wish to re-enable core dumps by setting ``disable_coredump'' to false in
the sudo.conf(5) file as follows:
Set disable_coredump false
See the sudo.conf(5) manual for more information.
sudo utilizes the following environment variables. The security policy
has control over the actual content of the command's environment.
EDITOR Default editor to use in -e (sudoedit) mode if neither
SUDO_EDITOR nor VISUAL is set.
MAIL In -i mode or when env_reset is enabled in sudoers, set
to the mail spool of the target user.
HOME Set to the home directory of the target user if -i or -H
are specified, env_reset or always_set_home are set in
sudoers, or when the -s option is specified and set_home
is set in sudoers.
PATH May be overridden by the security policy.
SHELL Used to determine shell to run with -s option.
SUDO_ASKPASS Specifies the path to a helper program used to read the
password if no terminal is available or if the -A option
SUDO_COMMAND Set to the command run by sudo.
SUDO_EDITOR Default editor to use in -e (sudoedit) mode.
SUDO_GID Set to the group ID of the user who invoked sudo.
SUDO_PROMPT Used as the default password prompt.
SUDO_PS1 If set, PS1 will be set to its value for the program
SUDO_UID Set to the user ID of the user who invoked sudo.
SUDO_USER Set to the login name of the user who invoked sudo.
To get a file listing of an unreadable directory:
$ sudo ls /usr/local/protected
To list the home directory of user yaz on a machine where the file system
holding ~yaz is not exported as root:
$ sudo -u yaz ls ~yaz
To edit the index.html file as user www:
$ sudo -u www vi ~www/htdocs/index.html
To view system logs only accessible to root and users in the adm group:
$ sudo -g adm view /var/log/syslog
To run an editor as jim with a different primary group:
$ sudo -u jim -g audio vi ~jim/sound.txt
To shut down a machine:
$ sudo shutdown -r +15 "quick reboot"
To make a usage listing of the directories in the /home partition. Note
that this runs the commands in a sub-shell to make the cd and file redi-
$ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"
su(1), stat(2), passwd(5), sudo.conf(5), sudoers(5), sudo_plugin(8),
See the HISTORY file in the sudo distribution
(http://www.sudo.ws/sudo/history.html) for a brief history of sudo.
Many people have worked on sudo over the years; this version consists of
code written primarily by:
Todd C. Miller
See the CONTRIBUTORS file in the sudo distribution
(http://www.sudo.ws/sudo/contributors.html) for an exhaustive list of
people who have contributed to sudo.
There is no easy way to prevent a user from gaining a root shell if that
user is allowed to run arbitrary commands via sudo. Also, many programs
(such as editors) allow the user to run commands via shell escapes, thus
/dev/fd/ directory, setuid shell scripts are generally safe).
If you feel you have found a bug in sudo, please submit a bug report at
Limited free support is available via the sudo-users mailing list, see
http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the
sudo is provided ``AS IS'' and any express or implied warranties, includ-
ing, but not limited to, the implied warranties of merchantability and
fitness for a particular purpose are disclaimed. See the LICENSE file
distributed with sudo or http://www.sudo.ws/sudo/license.html for com-
Sudo 1.8.9p5 December 8, 2013 Sudo 1.8.9p5
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