Linux Command


sudo -v [-AknS] [-a type] [-g group] [-h host] [-p prompt] [-u user]


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 5 minutes.

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 5 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:

-A 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 /etc/sudo.conf 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

-b The -b (background) option tells sudo to run the given com-
mand 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 back-
ground mode.

-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). Val-
ues 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 closefrom_override option.

-E The -E (preserve environment) option indicates to the secu-
rity 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.

-e 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 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 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 group.

-H 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

-h The -h (help) option causes sudo to print a short help mes-
sage to the standard output and exit.

-i [command]
The -i (simulate initial login) option runs the shell speci-
fied 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.

-K 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 caching.

-k [command]
When used alone, the -k (kill) option to sudo invalidates the
user’s cached credentials. The next time sudo is run a pass-
word will be required. This option does not require a pass-
word and was added to allow a user to revoke sudo permissions
from a .logout file. Not all security policies support cre-
dential caching.

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 cached credentials.

-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 speci-
fied 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 used.

-n 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 message and exit.

-P 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:

%H 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))

%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 prompt specified by the -p option will override the sys-
tem password prompt on systems that support PAM unless the
passprompt_override flag is disabled in sudoers.

-r role The -r (role) option causes the new (SELinux) security con-
text to have the role specified by role.

-S The -S (stdin) option causes sudo to read the password from
the standard input instead of the terminal device. The pass-
word 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.

-t type The -t (type) option causes the new (SELinux) security con-
text to have the type specified by type. If no type is spec-
ified, the default type is derived from the specified role.

-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’ privi-
leges. 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, #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 this.

-V 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.

-v 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 5 minutes (or whatever the timeout is set
to by the security policy) but does not run a command. Not
all security policies support cached credentials.

-- 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 the same restrictions as normal environment variables with
one important exception. 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 variables that would otherwise be forbidden. See
sudoers(5) for more information.

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