SUDO(8)			  BSD System Manager's Manual		       SUDO(8)

NAME
     sudo, sudoedit -- execute a command as another user

SYNOPSIS
     sudo -h | -K | -k | -V
     sudo -v [-AknS] [-a type] [-g group] [-h host] [-p prompt] [-u user]
     sudo -l [-AknS] [-a type] [-g group] [-h host] [-p prompt] [-U user]
	  [-u user] [command]
     sudo [-AbEHnPS] [-a type] [-C num] [-c class] [-g group] [-h host]
	  [-p prompt] [-r role] [-t type] [-T timeout] [-u user] [VAR=value]
	  [-i | -s] [command]
     sudoedit [-AknS] [-a type] [-C num] [-c class] [-g group] [-h host]
	  [-p prompt] [-T timeout] [-u user] file ...

DESCRIPTION
     sudo allows a permitted user to execute a command as the superuser or
     another user, as specified by the security policy.	 The invoking user's
     real (not effective) user ID is used to determine the user name with
     which to query 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, --askpass
		 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
		 error.

     -b, --background
		 Run the given command in the background.  Note that it is not
		 possible to use shell job control to manipulate background
		 processes started by sudo.  Most interactive commands will
		 fail to work properly in background mode.

     -C num, --close-from=num
		 Close all file descriptors greater than or equal to num
		 before executing a command.  Values less than three are not
		 permitted.  By default, sudo will close all open file
		 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.

     -E, --preserve-env
		 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.

     --preserve-env=list
		 Indicates to the security policy that the user wishes to add
		 the comma-separated list of environment variables to those
		 preserved from the user's environment.	 The security policy
		 may return an error if the user does not have permission 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.

		 To help prevent the editing of unauthorized files, the fol-
		 lowing restrictions are enforced unless explicitly allowed by
		 the security policy:

		 o  Symbolic links may not be edited (version 1.8.15 and
		    higher).

		 o  Symbolic links along the path to be edited are not fol-
		    lowed when the parent directory is writable by the invok-
		    ing user unless that user is root (version 1.8.16 and
		    higher).

		 o  Files located in a directory that is writable by the
		    invoking user may not be edited unless that user is root
		    (version 1.8.16 and higher).

		 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, --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
		 to group.

     -H, --set-home
		 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.

     -h, --help	 Display a short help message to the standard output and exit.

     -h host, --host=host
		 Run the command on the specified host if the security policy
		 plugin supports remote commands.  Note that the sudoers plug-
		 in does not currently support running remote commands.	 This
		 may also be used in conjunction with the -l option to list a
		 user's privileges for the remote host.

     -i, --login
		 Run the shell specified by the target user's password data-
		 base entry as a login shell.  This means that login-specific
		 resource files such as .profile, .bash_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.  Note that
		 most shells behave differently when a command is specified as
		 compared to an interactive session; consult the shell's man-
		 ual for details.  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, --remove-timestamp
		 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-
		 dential caching.

     -k, --reset-timestamp
		 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 a command is spec-
		 ified but not allowed by the policy, sudo will exit with a
		 status value of 1.

     -n, --non-interactive
		 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.

     -P, --preserve-groups
		 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 a member of.	The
		 real and effective group IDs, however, are still set to match
		 the target user.

     -p prompt, --prompt=prompt
		 Use a custom password prompt with optional escape sequences.
		 The following percent (`%') escape sequences 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
		     specified)

		 %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 default prompt specified
		 by either the security policy or the SUDO_PROMPT environment
		 variable.  On systems that use PAM, the custom prompt will
		 also override the prompt specified by a PAM module 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.

     -S, --stdin
		 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.

     -s, --shell
		 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.  Note
		 that most shells behave differently when a command is speci-
		 fied as compared to an interactive session; consult the
		 shell's manual for details.

     -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.

     -T timeout, --command-timeout=timeout
		 Used to set a timeout for the command.	 If the timeout
		 expires before the command has exited, the command will be
		 terminated.  The security policy may restrict the ability to
		 set command timeouts.	The sudoers policy requires that user-
		 specified timeouts be explicitly enabled.

     -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
		 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, --version
		 Print the sudo version string as well as 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, --validate
		 Update the user's cached credentials, authenticating the user
		 if necessary.	For the sudoers plugin, this extends the sudo
		 timeout for another 5 minutes by default, but does not run a
		 command.  Not all security policies support cached creden-
		 tials.

     --		 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-
     mation.

COMMAND EXECUTION
     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)

   Process model
     There are two distinct ways sudo can run a command.

     If an I/O logging plugin is configured or if the security policy explic-
     itly requests it, a new pseudo-terminal (``pty'') is allocated and
     fork(2) is used to create a second sudo process, referred to as the
     monitor.  The monitor creates a new terminal session with itself as the
     leader and the pty as its controlling terminal, calls fork(2), sets up
     the execution environment as described above, and then uses the execve(2)
     system call to run the command in the child process.  The monitor exists
     to relay job control signals between the user's existing terminal and the
     pty the command is being run in.  This makes it possible to suspend and
     resume the command.  Without the monitor, the command would be in what
     POSIX terms an ``orphaned process group'' and it would not receive any
     job control signals from the kernel.  When the command exits or is termi-
     nated by a signal, the monitor passes the command's exit status to the
     main sudo process and exits.  After receiving the command's exit status,
     the main sudo passes the command's exit status to the security policy's
     close function and exits.

     If no pty is used, sudo calls fork(2), sets up the execution environment
     as described above, and uses the execve(2) system call to run the command
     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.	As a special case, if the policy plugin does
     not define a close function, sudo will execute the command directly
     instead of calling fork(2) first.	The sudoers policy plugin will only
     define a close function when I/O logging is enabled, a pty is required,
     or the pam_session or pam_setcred options are enabled.  Note that
     pam_session and pam_setcred are enabled by default on systems using PAM.

   Signal handling
     When the command is run as a child of the sudo process, sudo will relay
     signals it receives to the command.  The SIGINT and SIGQUIT signals are
     only relayed when the command is being run in a new pty or when the sig-
     nal was sent by a user process, not the kernel.  This prevents the com-
     mand from receiving SIGINT twice each time the user enters 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
     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(5) man-
     ual for more information about the sudo plugin architecture.

EXIT VALUE
     Upon successful execution of a command, the exit status from sudo will be
     the exit status of the program that was executed.	If the command termi-
     nated due to receipt of a signal, sudo will send itself the same signal
     that terminated the command.

     If the -l option was specified without a command, sudo will exit with a
     value of 0 if the user is allowed to run sudo and they authenticated suc-
     cessfully (as required by the security policy).  If a command is speci-
     fied with the -l option, the exit value will only be 0 if the command is
     permitted by the security policy, otherwise it will be 1.

     If there is an authentication failure, a configuration/permission problem
     or if the given command cannot be executed, sudo exits with a value of 1.
     In the latter case, the error string is printed to the standard error.
     If sudo cannot stat(2) one or more entries in the user's PATH, an error
     is printed to the standard error.	(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 PATH is on a
     machine that is currently unreachable.

SECURITY NOTES
     sudo tries to be safe when executing external commands.

     To prevent command spoofing, sudo checks "." and "" (both denoting cur-
     rent 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 envi-
     ronment variable is not modified and is passed unchanged to the program
     that sudo executes.

     Users should never be granted sudo privileges to execute files that are
     writable by the user or that reside in a directory that is writable by
     the user.	If the user can modify or replace the command there is no way
     to limit what additional commands they can run.

     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 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).  This historical practice dates from a time
     when most operating systems allowed setuid processes to dump core by
     default.  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.

ENVIRONMENT
     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	      Set to the mail spool of the target user when the -i
		      option is specified or when env_reset is enabled in
		      sudoers (unless MAIL is present in the env_keep list).

     HOME	      Set to the home directory of the target user when the -i
		      or -H options are specified, when the -s option is spec-
		      ified and set_home is set in sudoers, when
		      always_set_home is enabled in sudoers, or when env_reset
		      is enabled in sudoers and HOME is not present in the
		      env_keep list.

     LOGNAME	      Set to the login name of the target user when the -i
		      option is specified, when the set_logname option is
		      enabled in sudoers or when the env_reset option is
		      enabled in sudoers (unless LOGNAME is present in the
		      env_keep list).

     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
		      is specified.

     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 unless the -p option
		      was specified.

     SUDO_PS1	      If set, PS1 will be set to its value for the program
		      being run.

     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.

     USER	      Set to the same value as LOGNAME, described above.

     USERNAME	      Same as USER.

     VISUAL	      Default editor to use in -e (sudoedit) mode if
		      SUDO_EDITOR is not set.

FILES
     /etc/sudo.conf	       sudo front end configuration

EXAMPLES
     Note: the following examples assume a properly configured security pol-
     icy.

     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:

	   $ sudoedit -u www ~www/htdocs/index.html

     To view system logs only accessible to root and users in the adm group:

	   $ sudo -g adm more /var/log/syslog

     To run an editor as jim with a different primary group:

	   $ sudoedit -u jim -g audio ~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-
     rection work.

	   $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"

SEE ALSO
     su(1), stat(2), passwd(5), sudo.conf(5), sudoers(5), sudo_plugin(5),
     sudoreplay(8), visudo(8)

HISTORY
     See the HISTORY file in the sudo distribution (https://www.sudo.ws/his-
     tory.html) for a brief history of sudo.

AUTHORS
     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
     (https://www.sudo.ws/contributors.html) for an exhaustive list of people
     who have contributed to sudo.

CAVEATS
     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 sudo's checks.  However, on most systems it is possible to pre-
     vent shell escapes with the sudoers(5) plugin's noexec functionality.

     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).

BUGS
     If you feel you have found a bug in sudo, please submit a bug report at
     https://bugzilla.sudo.ws/

SUPPORT
     Limited free support is available via the sudo-users mailing list, see
     https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search
     the archives.

DISCLAIMER
     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 https://www.sudo.ws/license.html for complete
     details.

Sudo 1.8.23			March 21, 2018			   Sudo 1.8.23