sudo, sudoedit - execute a command as another user
-g group name
-u user name
-g group name
] [ -U user name
[-u user name
] [ -C fd
-g group name
-u user name
] [ VAR
] [ -C fd
-g group name
-u user name
] file ...
allows a permitted user to execute a command
as the superuser
or another user, as specified by the security policy. The real and effective
uid and gid 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).
supports a plugin architecture for security policies and
input/output logging. Third parties can develop and distribute their own
policy and I/O logging modules to work seamlessly with the sudo
end. The default security policy is sudoers
, which is configured via
the file /etc/sudoers
, or via LDAP. See the PLUGINS section for more
The security policy determines what privileges, if any, a user has to run
. The policy may require that users authenticate themselves with a
password or another authentication mechanism. If authentication is required,
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
again for a period of time without requiring authentication. The
policy caches credentials for 15 minutes, unless overridden in
. 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
Security policies may log successful and failed attempts to use sudo
an I/O plugin is configured, the running command's input and output may be
logged as well.
accepts the following command line options:
- Normally, if sudo requires a password, it will read
it from the user's terminal. If the -A (askpass) option is
specified, a (possibly graphical) helper program is executed to read the
user's password and output the password to the standard output. If the
SUDO_ASKPASS environment variable is set, it specifies the path to the
helper program. Otherwise, if /etc/sudo.conf contains a line
specifying the askpass program, 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 error.
- The -b (background) option tells sudo
to run the given command in the background. Note that if you use the
-b option you cannot use shell job control to manipulate the
process. Most interactive commands will fail to work properly in
- -C fd
- Normally, sudo will close all open file descriptors
other than standard input, standard output and standard error. The
-C ( close from) option allows the user to specify a
starting point above the standard error (file descriptor three). Values
less than three are not permitted. The security policy may restrict the
user's ability to use the -C option. The sudoers policy only
permits use of the -C option when the administrator has enabled the
- The -E (preserve environment) option
indicates to the security policy that the user wishes to preserve their
existing environment variables. The security policy may return an error if
the -E option is specified and the user does not have permission to
preserve the environment.
- The -e (edit) option indicates that, instead
of running a command, the user wishes to edit one or more files. In lieu
of a command, the string "sudoedit" is used when consulting the
security policy. If the user is authorized by the policy, the following
steps are taken:
- Temporary copies are made of the files to be edited with
the owner set to the invoking user.
- 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.
- If they have been modified, the temporary files are copied
back to their original location and the temporary versions are
Unless explicitly allowed by the security policy, symbolic links will not be
opened. This helps prevent the editing of unauthorized files when the file is
located in a user-writable directory. Versions of <<sudo> prior to
1.8.5p2-1+nmu3+deb7u1 do not have this restriction. Users are never allowed to
edit device special files.
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
- Normally, sudo runs a command with the primary group
set to the one specified by the password database for the user the command
is being run as (by default, root). The -g (group) option
causes sudo to run the command with the primary group set to
group instead. To specify a gid instead of a group
name, use #gid. When running commands 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 (not root). In either case, the primary group will be set to
- The -H (HOME) option requests that the
security policy set the HOME environment variable to the home directory of
the target user (root by default) as specified by the password database.
Depending on the policy, this may be the default behavior.
- The -h (help) option causes sudo to
print a short help message to the standard output and exit.
- -i [command]
- The -i (simulate initial login) option runs
the shell specified by the password database entry of the target user 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 security policy shall initialize the environment to a minimal set of
variables, similar to what is present when a user logs 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.
- The -K (sure kill) option is like -k
except that it removes the user's cached credentials entirely and may not
be used in conjunction with a command or other option. This option does
not require a password. Not all security policies support credential
- -k [command]
- When used alone, the -k (kill) option to
sudo invalidates the user's cached credentials. 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
permissions from a .logout file. Not all security policies support
When used in conjunction with a command or an option that may require a
password, the -k 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
- -l[l] [command]
- If no command is specified, the -l
(list) option will list the allowed (and forbidden) commands for
the invoking user (or the user specified by the -U option) on the
current host. 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 specified but
not allowed, sudo will exit with a status value of 1. If the
-l option is specified with an l argument (i.e. -ll),
or if -l is specified multiple times, a longer list format is
- The -n (non-interactive) option prevents
sudo from prompting the user for a password. If a password is
required for the command to run, sudo will display an error
messages and exit.
- The -P (preserve group vector) option
causes sudo to preserve the invoking user's group vector unaltered.
By default, the sudoers policy will initialize the group vector to
the list of groups the target user is in. The real and effective group
IDs, however, are still set to match the target user.
- -p prompt
- The -p (prompt) option allows you to override
the default password prompt and use a custom one. The following percent
(`%') escapes are supported by the sudoers policy:
- expanded to the host name including the domain name (on if
the machine's host name is fully qualified or the fqdn option is
set in sudoers(5))
- expanded to the local host name without the domain
- expanded to the name of the user whose password is being
requested (respects the rootpw, targetpw and runaspw
flags in sudoers(5))
- expanded to the login name of the user the command will be
run as (defaults to root unless the -u option is also specified)
- expanded to the invoking user's login name
- two consecutive % characters are collapsed into a single %
The prompt specified by the -p
option will override the system password
prompt on systems that support PAM unless the passprompt_override
is disabled in sudoers
- The -S (stdin) option causes sudo to
read the password from the standard input instead of the terminal device.
The password must be followed by a newline character.
- -s [command]
- The -s (shell) option runs the shell
specified by the SHELL environment variable if it is set or the
shell as specified in the password database. 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.
- -U user
- The -U (other user) option is used in
conjunction with the -l option to specify the user whose privileges
should be listed. The security policy may restrict listing other users'
privileges. The sudoers policy only allows root or a user with the
ALL privilege on the current host to use this option.
- -u user
- The -u (user) option causes sudo to
run the specified command as a user other than root. To specify a
uid instead of a user name, use #uid. When running
commands as a uid, many shells require that the '#' be escaped with
a backslash ('\'). Security policies may restrict uids to those
listed in the password database. The sudoers policy allows
uids that are not in the password database as long as the
targetpw option is not set. Other security policies may not support
- The -V (version) option causes sudo to
print its version string and the version string of the security policy
plugin and any I/O plugins. If the invoking user is already root the
-V option will display the arguments passed to configure when
sudo was built and plugins may display more verbose information
such as default options.
- When given the -v (validate) option,
sudo will update the user's cached credentials, authenticating the
user's password if necessary. For the sudoers plugin, this extends
the sudo timeout for another 15 minutes (or whatever the timeout is
set to in sudoers) but does not run a command. Not all security
policies support cached credentials.
- The -- option indicates that sudo should stop
processing command line arguments.
Environment variables to be set for the command may also be passed on the
command line in the form of VAR
. Variables passed on the
command line are subject to the same restrictions as normal environment
variables with one important exception. If the setenv
option is set in
, the command to be run has the SETENV tag set or the command
matched is ALL, the user may set variables that would otherwise be forbidden.
for more information.
Plugins are dynamically loaded based on the contents of the
file. If no /etc/sudo.conf
file is present, or it
contains no Plugin lines, sudo
will use the traditional sudoers
security policy and I/O logging, which corresponds to the following
# Default /etc/sudo.conf file
# Plugin plugin_name plugin_path plugin_options ...
# Path askpass /path/to/askpass
# Path noexec /path/to/sudo_noexec.so
# Debug sudo /var/log/sudo_debug all@warn
# Set disable_coredump true
# The plugin_path is relative to /usr/libexec unless
# fully qualified.
# The plugin_name corresponds to a global symbol in the plugin
# that contains the plugin interface structure.
# The plugin_options are optional.
Plugin policy_plugin sudoers.so
Plugin io_plugin sudoers.so
A Plugin line consists of the Plugin keyword, followed by the symbol_name
and the path
to the shared object containing the plugin. The
is the name of the struct policy_plugin or struct io_plugin
in the plugin shared object. The path
may be fully qualified or
relative. If not fully qualified it is relative to the /usr/libexec
directory. Any additional parameters after the path
are passed as
arguments to the plugin's open
function. Lines that don't begin with
Plugin, Path, Debug or Set are silently ignored.
For more information, see the sudo_plugin(8)
A Path line consists of the Path keyword, followed by the name of the path to
set and its value. E.g.
Path noexec /usr/lib/sudo/sudo_noexec.so
Path askpass /usr/X11R6/bin/ssh-askpass
The following plugin-agnostic paths may be set in the /etc/sudo.conf
- The fully qualified path to a helper program used to read
the user's password when no terminal is available. This may be the case
when sudo is executed from a graphical (as opposed to text-based)
application. The program specified by askpass should display the
argument passed to it as the prompt and write the user's password to the
standard output. The value of askpass may be overridden by the
SUDO_ASKPASS environment variable.
- The fully-qualified path to a shared library containing
dummy versions of the execv(), execve() and fexecve()
library functions that just return an error. This is used to implement the
noexec functionality on systems that support LD_PRELOAD or its
equivalent. Defaults to /usr/lib/sudo/sudo_noexec.so.
versions 1.8.4 and higher support a flexible debugging framework
that can help track down what sudo
is doing internally if there is a
A Debug line consists of the Debug keyword, followed by the name of the program
to debug ( sudo
), the debug file name
and a comma-separated list of debug flags. The debug flag syntax used by
and the sudoers
plugin is subsystem
but the plugin is free to use a different format so long as it does not
include a command ,.
Debug sudo /var/log/sudo_debug all@warn,plugin@info
would log all debugging statements at the warn
level and higher in
addition to those at the info
level for the plugin subsystem.
Currently, only one Debug entry per program is supported. The sudo Debug entry
is shared by the sudo
front end, sudoedit
and the plugins. A
future release may add support for per-plugin Debug lines and/or support for
multiple debugging files for a single program.
The priorities used by the sudo
front end, in order of decreasing
severity, are: crit
. Each priority, when
specified, also includes all priorities higher than it. For example, a
priority of notice
would include debug messages logged at notice
The following subsystems are used by sudo
- matches every subsystem
- command line argument processing
- user conversation
- command execution
- sudo main function
- network interface handling
- communication with the plugin
- plugin configuration
- pseudo-tty related code
- SELinux-specific handling
- utility functions
- utmp handling
Upon successful execution of a program, the exit status from sudo
simply be the exit status of the program that was executed.
exits with a value of 1 if there is a
configuration/permission problem or if sudo
cannot execute the given
command. In the latter case the error string is printed to the standard error.
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
to return "permission denied" is if you are running
an automounter and one of the directories in your PATH is on a machine that is
tries to be safe when executing external commands.
To prevent command spoofing, sudo
checks "." and ""
(both denoting current directory) last when searching for a command in the
user's PATH (if one or both are in the PATH). Note, however, that the actual
PATH environment variable is not
modified and is passed unchanged to
the program that sudo
Please note that sudo
will normally only log the command it explicitly
runs. If a user runs a command such as sudo su or sudo sh, subsequent commands
run from that shell are not subject to sudo
's security policy. The same
is true for commands that offer shell escapes (including most editors). If I/O
logging is enabled, subsequent commands will have their 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 inadvertently 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
disables 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 /etc/sudo.conf
Set disable_coredump false
Note that by default, most operating systems disable core dumps from setuid
programs, which includes sudo
. To actually get a sudo
you may need to enable core dumps for setuid processes. On BSD and Linux
systems this is accomplished via the sysctl command, on Solaris the coreadm
command can be used.
utilizes the following environment variables. The security policy
has control over the content of the command's environment.
- Default editor to use in -e (sudoedit) mode if
neither SUDO_EDITOR nor VISUAL is set
- In -i mode or when env_reset is enabled in
sudoers, set to the mail spool of the target user
- 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
- May be overridden by the security policy.
- Used to determine shell to run with -s option
- Specifies the path to a helper program used to read the
password if no terminal is available or if the -A option is
- Set to the command run by sudo
- Default editor to use in -e (sudoedit) mode
- Set to the group ID of the user who invoked sudo
- Used as the default password prompt
- If set, PS1 will be set to its value for the program being
- Set to the user ID of the user who invoked sudo
- Set to the login of the user who invoked sudo
- Set to the target user (root unless the -u option is
- Default editor to use in -e (sudoedit) mode if
SUDO_EDITOR is not set
- sudo front end configuration
Note: the following examples assume a properly configured security policy.
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 shutdown 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 redirection
$ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"
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
for a list of people who have
contributed to sudo
See the HISTORY file in the sudo
for a brief history of 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 avoiding
's checks. However, on most systems it is possible to prevent shell
escapes with the sudoers(5)
It is not meaningful to run the cd command directly via sudo, e.g.,
$ sudo cd /usr/local/protected
since when the command exits the parent process (your shell) will still be the
same. Please see the EXAMPLES section for more information.
Running shell scripts via sudo
can expose the same kernel bugs that make
setuid shell scripts unsafe on some operating systems (if your OS has a
/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
to subscribe or search the
is provided ``AS IS'' and any express or implied warranties,
including, but not limited to, the implied warranties of merchantability and
fitness for a particular purpose are disclaimed. See the LICENSE file
distributed with sudo