] file ...
sudoallows a permitted user to execute a command as the superuser or another user, as specified by the sudoers file. See the COMMAND EXECUTION section below for more details.
sudodetermines who is an authorized user by consulting the file /etc/sudoers. By running
-voption, a user can update the time stamp without running a command. If authentication is required,
sudowill exit if the user's password is not entered within a configurable time limit. The default password prompt timeout is
5minutes. When invoked as
-eoption (described below), is implied. The options are as follows:
sudorequires 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_ASKPASSenvironment variable is set, it specifies the path to the helper program. Otherwise, the value specified by the askpass option in sudoers(5) is used. If no askpass program is available,
sudowill exit with an error.
-a(authentication type) option causes
sudoto use the specified authentication type when validating the user, as allowed by /etc/login.conf. The system administrator may specify a list of sudo-specific authentication methods by adding an “auth-sudo” entry in /etc/login.conf. This option is only available on systems that support BSD authentication.
-b(background) option tells
sudoto run the given command in the background. Note that if you use the
-boption you cannot use shell job control to manipulate the process. Most interactive commands will fail to work properly in background mode.
sudowill 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. This option is only available when the administrator has enabled the closefrom_override option in sudoers(5).
-c(class) option causes
sudoto run the specified command with resources limited by the specified login class. The class argument can be either a class name as defined in /etc/login.conf, or a single ‘
-’ character. Specifying a class of
-indicates that the command should be run restricted by the default login capabilities for the user the command is run as. If the class argument specifies an existing user class, the command must be run as root, or the
sudocommand must be run from a shell that is already root. This option is only available on systems with BSD login classes.
-E(preserve environment) option will override the env_reset option in sudoers(5). It is only available when either the matching command has the
SETENVtag or the setenv option is set in sudoers(5).
sudowill return an error if the
-Eoption is specified and the user does not have permission to preserve the environment.
-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 sudoers file. If the user is authorized by sudoers, the following steps are taken:
EDITORenvironment variables (in that order) is run to edit the temporary files. If none of
EDITORare set, the first program listed in the editor sudoers(5) option is used.
sudois 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.
sudoruns 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
sudoto 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
-uoption 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(HOME) option option sets the
HOMEenvironment variable to the home directory of the target user (root by default) as specified by the password database. The default handling of the
HOMEenvironment variable depends on sudoers(5) settings. By default,
HOMEif env_reset or always_set_home are set, or if set_home is set and the
-soption is specified on the command line.
-h(help) option causes
sudoto print a short help message to the standard output and exit.
-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
-coption. If no command is specified, an interactive shell is executed.
sudoattempts to change to that user's home directory before running the shell. It also initializes the environment to a minimal set of variables, similar to what is present when a user logs in. The Command environment section below documents in detail how the
-ioption affects the environment in which a command is run.
-K(sure kill) option is like
-kexcept that it removes the user's time stamp file entirely and may not be used in conjunction with a command or other option. This option does not require a password.
-k(kill) option to
sudoinvalidates the user's time stamp file. The next time
sudois run a password will be required. This option does not require a password and was added to allow a user to revoke
sudopermissions from a .logout file. When used in conjunction with a command or an option that may require a password, the
-koption will cause
sudoto ignore the user's time stamp file. As a result,
sudowill prompt for a password (if one is required by sudoers) and will not update the user's time stamp file.
-L(list defaults) option will list the parameters that may be set in a Defaults line along with a short description for each. This option will be removed from a future version of
-l(list) option will list the allowed (and forbidden) commands for the invoking user (or the user specified by the
-Uoption) on the current host. If a command is specified and is permitted by sudoers, the fully-qualified path to the command is displayed along with any command line arguments. If command is specified but not allowed,
sudowill exit with a status value of 1. If the
-loption is specified with an l argument (i.e.
-ll), or if
-lis specified multiple times, a longer list format is used.
-n(non-interactive) option prevents
sudofrom prompting the user for a password. If a password is required for the command to run,
sudowill display an error message and exit.
-P(preserve group vector) option causes
sudoto preserve the invoking user's group vector unaltered. By default,
sudowill 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) option allows you to override the default password prompt and use a custom one. The following percent (‘
%’) escapes are supported:
-uoption is also specified)
%’ characters are collapsed into a single ‘
-poption will override the system password prompt on systems that support PAM unless the passprompt_override flag is disabled in sudoers.
-r(role) option causes the new (SELinux) security context to have the role specified by role.
-S(stdin) option causes
sudoto read the password from the standard input instead of the terminal device. The password must be followed by a newline character.
-s(shell) option runs the shell specified by the
SHELLenvironment 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
-coption. If no command is specified, an interactive shell is executed.
-t(type) option causes the new (SELinux) security context to have the type specified by type. If no type is specified, the default type is derived from the specified role.
-U(other user) option is used in conjunction with the
-loption to specify the user whose privileges should be listed. Only root or a user with the
ALLprivilege on the current host may use this option.
-u(user) option causes
sudoto 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 (‘
\’). Note that if the targetpw Defaults option is set (see sudoers(5)), it is not possible to run commands with a uid not listed in the password database.
-V(version) option causes
sudoto print its version string and exit. If the invoking user is already root the
-Voption will display the arguments passed to configure when
sudowas built as well a list of the defaults
sudowas compiled with as well as the machine's local network addresses.
sudowill update the user's time stamp file, authenticating the user's password if necessary. This extends the
sudotimeout for another
5minutes (or whatever the timeout is set to in sudoers) but does not run a command.
--option indicates that
sudoshould stop processing command line arguments.
SETENVtag set or the command matched is
ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information.
sudorequires that most users authenticate themselves by default. A password is not required if the invoking user is root, if the target user is the same as the invoking user, or if the authentication has been disabled for the user or command in the sudoers file. Unlike su(1), when
sudorequires authentication, it validates the invoking user's credentials, not the target user's (or root's) credentials. This can be changed via the rootpw, targetpw and runaspw Defaults entries in sudoers. If a user who is not listed in sudoers tries to run a command via
sudo, mail is sent to the proper authorities. The address used for such mail is configurable via the mailto sudoers Defaults entry and defaults to
root. Note that mail will not be sent if an unauthorized user tries to run
-voption. This allows users to determine for themselves whether or not they are allowed to use
sudois run by root and the
SUDO_USERenvironment variable is set, its value will be used to determine who the actual user is. This can be used by a user to log commands through
sudoeven when a root shell has been invoked. It also allows the
-eoption to remain useful even when invoked via a sudo-run script or program. Note, however, that the sudoers lookup is still done for root, not the user specified by
sudouses time stamp files for credential caching. Once a user has been authenticated, the time stamp is updated and the user may then use sudo without a password for a short period of time (
5minutes unless overridden by the timeout option). By default,
sudouses a tty-based time stamp which means that there is a separate time stamp for each of a user's login sessions. The tty_tickets option can be disabled to force the use of a single time stamp for all of a user's sessions.
sudocan log both successful and unsuccessful attempts (as well as errors) to syslog(3), a log file, or both. By default,
sudowill log via syslog(3) but this is changeable via the syslog and logfile Defaults settings.
sudoalso supports logging a command's input and output streams. I/O logging is not on by default but can be enabled using the log_input and log_output Defaults flags as well as the
sudoprovides a means to restrict which variables from the user's environment are inherited by the command to be run. There are two distinct ways sudoers can be configured to handle with environment variables. By default, the env_reset option is enabled. This causes commands to be executed with a new, minimal environment. On AIX (and Linux systems without PAM), the environment is initialized with the contents of the /etc/environment file. On BSD systems, if the use_loginclass option is enabled, the environment is initialized based on the path and setenv settings in /etc/login.conf. The new environment contains the
SUDO_*variables in addition to variables from the invoking process permitted by the env_check and env_keep options. This is effectively a whitelist for environment variables. If, however, the env_reset option is disabled, any variables not explicitly denied by the env_check and env_delete options are inherited from the invoking process. In this case, env_check and env_delete behave like a blacklist. Since it is not possible to blacklist all potentially dangerous environment variables, use of the default env_reset behavior is encouraged. In all cases, environment variables with a value beginning with
()are removed as they could be interpreted as bash functions. The list of environment variables that
sudoallows or denies is contained in the output of “
sudo -V” when run as root. Note that the dynamic linker on most operating systems will remove variables that can control dynamic linking from the environment of setuid executables, including
sudo. Depending on the operating system this may include
SHLIB_PATH, and others. These type of variables are removed from the environment before
sudoeven begins execution and, as such, it is not possible for
sudoto preserve them. As a special case, if
-ioption (initial login) is specified,
sudowill initialize the environment regardless of the value of env_reset. The
TERMvariables remain unchanged;
LOGNAMEare set based on the target user. On AIX (and Linux systems without PAM), the contents of /etc/environment are also included. On BSD systems, if the use_loginclass option is enabled, the path and setenv variables in /etc/login.conf are also applied. All other environment variables are removed. Finally, if the env_file option is defined, any variables present in that file will be set to their specified values as long as they would not conflict with an existing environment variable.
sudoexecutes a command, the sudoers file specifies the execution envionment for the command. Typically, 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
-Poption was specified). The sudoers file settings affect the following execution parameters:
sudohas been configured with PAM support or if I/O logging is enabled,
sudomust wait until the command has completed before it will exit. In the case of PAM,
sudomust remain running so that it can close the PAM session when the command is finished. If neither PAM nor I/O logging are configured,
sudowill execute the command without calling fork(2). In either case,
sudosets up the execution environment as described above, and calls the execve system call (potentially in a child process). If I/O logging is enabled, a new pseudo-terminal (“pty”) is created and a second
sudoprocess is used to relay job control signals between the user's existing pty and the new pty the command is being run in. This extra process makes it possible to, for example, suspend and resume the command. Without it, the command would be in what POSIX terms an “orphaned process group” and it would not receive any job control signals.
sudoprocess (due to PAM or I/O logging),
sudowill relay signals it receives to the command. Unless the command is being run in a new pty, the
SIGQUITsignals are not relayed unless they are sent by a user process, not the kernel. Otherwise, the command would receive
SIGINTtwice every time the user entered control-C. Some signals, such as
SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule,
SIGTSTPshould be used instead of
SIGSTOPwhen you wish to suspend a command being run by
sudo. As a special case,
sudowill not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) command sends
SIGTERMto all non-system processes other than itself before rebooting the systyem. This prevents
sudofrom relaying the
SIGTERMsignal 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, however, that this check only applies to the command run by
sudoand not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via
sudomay 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).
sudoexits with a value of 1 if there is a configuration/permission problem or if
sudocannot execute the given command. In the latter case the error string is printed to the standard error. If
sudocannot 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 automounter and one of the directories in your
PATHis on a machine that is currently unreachable.
sudocan log events using either syslog(3) or a simple log file. In each case the log format is almost identical.
date hostname progname: username : TTY=ttyname ; PWD=cwd ; \ USER=runasuser ; GROUP=runasgroup ; TSID=logid ; \ ENV=env_vars COMMAND=command
sudowas run on. This field is only present when logging via syslog(3).
sudowas run on, or “unknown” if there was no terminal present.
sudowas run in.
-noption was specified but a password was required.
sudowill log a message and, in most cases, send a message to the administrator via email. Possible errors include:
sudoencountered an error when parsing the specified file. In some cases, the actual error may be one line above or below the line number listed, depending on the type of error.
sudofrom running, but the sudoers file should be checked using
sudotries to open sudoers using group permissions to avoid this problem.
sudowill split up log messages that are larger than 960 characters (not including the date, hostname, and the string “sudo”). When a message is split, additional parts will include the string “(command continued)” after the user name and before the continued command line arguments. /var/log/sudo. When logging to a file, sudoers uses a format similar to syslog(3), with a few important differences:
!’), word wrap will be disabled.
sudotries to be safe when executing external commands. To prevent command spoofing,
sudochecks "." 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
PATHenvironment variable is not modified and is passed unchanged to the program that
sudowill check the ownership of its time stamp directory (/var/adm/sudo by default) and ignore the directory's contents if it is not owned by root or if it is writable by a user other than root. On systems that allow non-root users to give away files via chown(2), if the time stamp directory is located in a world-writable directory (e.g., /tmp), it is possible for a user to create the time stamp directory before
sudois run. However, because
sudochecks the ownership and mode of the directory and its contents, the only damage that can be done is to “hide” files by putting them in the time stamp dir. This is unlikely to happen since once the time stamp dir is owned by root and inaccessible by any other user, the user placing files there would be unable to get them back out.
sudowill not honor time stamps set far in the future. Time stamps with a date greater than current_time + 2 *
TIMEOUTwill be ignored and sudo will log and complain. This is done to keep a user from creating his/her own time stamp with a bogus date on systems that allow users to give away files if the time stamp directory is located in a world-writable directory. On systems where the boot time is available,
sudowill ignore time stamps that date from before the machine booted. Since time stamp files live in the file system, they can outlive a user's login session. As a result, a user may be able to login, run a command with
sudoafter authenticating, logout, login again, and run
sudowithout authenticating so long as the time stamp file's modification time is within
5minutes (or whatever the timeout is set to in sudoers). When the tty_tickets sudoers option is enabled, the time stamp has per-tty granularity but still may outlive the user's session. On Linux systems where the devpts filesystem is used, Solaris systems with the devices filesystem, as well as other systems that utilize a devfs filesystem that monotonically increase the inode number of devices as they are created (such as Mac OS X),
sudois able to determine when a tty-based time stamp file is stale and will ignore it. Administrators should not rely on this feature as it is not universally available. Please note that
sudowill normally only log the command it explicitly runs. If a user runs a command such as
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
sudoto 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,
sudodisables core dumps by default while it is executing (they are re-enabled for the command that is run). For information on the security implications of sudoers entries, please see the SECURITY NOTES section in sudoers(5).
sudoutilizes the following environment variables:
-e(sudoedit) mode if neither
-imode or when env_reset is enabled in sudoers, set to the mail spool of the target user.
-Hare specified, env_reset or always_set_home are set in sudoers, or when the
-soption is specified and set_home is set in sudoers.
-Aoption is specified.
PS1will be set to its value for the program being run.
-uoption is specified).
-e(sudoedit) mode if
SUDO_EDITORis not set.
-imode on AIX and Linux systems
$ sudo ls /usr/local/protected
$ sudo -u yaz ls ~yaz
$ sudo -u www vi ~www/htdocs/index.html
$ sudo -g adm view /var/log/syslog
$ sudo -u jim -g audio vi ~jim/sound.txt
$ sudo shutdown -r +15 "quick reboot"
cdand file redirection work.
$ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"
sudodistribution (https://www.sudo.ws/sudo/history.html) for a brief history of sudo.
sudoover the years; this version consists of code written primarily by:
sudodistribution (https://www.sudo.ws/sudo/contributors.html) for an exhaustive list of people who have contributed to
sudo. Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding
sudo's checks. However, on most systems it is possible to prevent shell escapes with
sudo ' snoexec functionality. See the sudoers(5) manual for details. It is not meaningful to run the
cdcommand directly via sudo, e.g.,
$ sudo cd /usr/local/protected
sudocan 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).
sudo, please submit a bug report at https://www.sudo.ws/sudo/bugs/ https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives.
sudois 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
sudoor https://www.sudo.ws/sudo/license.html for complete details.