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SUDO(8)			FreeBSD	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] [-u user] [VAR=value]	[-i | -s]
	  [command]
     sudoedit [-AknS] [-a type]	[-C num] [-c class] [-g	group] [-h host]
	  [-p prompt] [-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
     /usr/local/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.

     -c	class, --login-class=class
		 Run the command with resource limits and scheduling priority
		 of the	specified login	class.	The class argument can be
		 either	a class	name as	defined	in /etc/login.conf, or a sin-
		 gle `-' character.  If	class is -, the	default	login class of
		 the target user will be used.	Otherwise, the command must be
		 run as	the superuser (user ID 0), or sudo must	be run from a
		 shell that is already running as the superuser.  If the com-
		 mand is being run as a	login shell, additional
		 /etc/login.conf settings, such	as the umask and environment
		 variables, will be applied, if	present.  This option is only
		 available on systems with BSD login classes.

     -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.

     -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.

		 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	1.8.15 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, --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 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.

     -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 command is speci-
		 fied but not allowed, 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 system password prompt on
		 systems that support PAM unless the passprompt_override flag
		 is disabled in	sudoers.

     -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.

     -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
		 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	 BSD login class

     +o	 scheduling priority (aka nice value)

   Process model
     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
     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.  As a special case, if the policy	plugin does not	define a close
     function and no pty is required, 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.  Unless the command is	being run in a
     new pty, the 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 sig-
     nals, 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 /usr/local/etc/sudo.conf	file and the
     sudo_plugin(8) manual for more information	about the sudo plugin archi-
     tecture.

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 signal	that
     terminated	the command.

     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
     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 rea-
     son 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.  Likewise,	users should
     never be granted sudoedit permission to edit a file that resides in a
     directory the user	has write access to.  A	user with directory write
     access could replace the legitimate file with a link to some other, arbi-
     trary, file.  Starting with version 1.8.15, sudoedit will refuse to open
     a symbolic	link unless the	security policy	explicitly permits it.	How-
     ever, it is still possible	to create a hard link if the directory is
     writable and the link target resides on the same file system.

     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.

     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
     /usr/local/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:

	   $ 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-
     rection work.

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

SEE ALSO
     su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudoers(5),
     sudo_plugin(8), sudoreplay(8), visudo(8)

HISTORY
     See the HISTORY file in the sudo distribution (http://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
     (http://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
     http://bugzilla.sudo.ws/

SUPPORT
     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
     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 http://www.sudo.ws/license.html for complete
     details.

Sudo 1.8.15		      September	27, 2015		   Sudo	1.8.15

NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER

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