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SUDO(8)			     MAINTENANCE COMMANDS		       SUDO(8)

NAME
       sudo, sudoedit -	execute	a command as another user

SYNOPSIS
       sudo -h | -K | -k | -L |	-l | -V	| -v

       sudo [-bEHPS] [-c class|-] [-p prompt] [-u username|#uid] [VAR=value]
       {-i | -s	| command}

       sudoedit	[-S] [-c class|-] [-p prompt] [-u username|#uid] file ...

DESCRIPTION
       sudo allows a permitted user to execute a command as the	superuser or
       another user, as	specified in the sudoers file.	The real and effective
       uid and gid are set to match those of the target	user as	specified in
       the passwd file and the group vector is initialized based on the	group
       file (unless the	-P option was specified).  If the invoking user	is
       root or if the target user is the same as the invoking user, no pass-
       word is required.  Otherwise, sudo requires that	users authenticate
       themselves with a password by default (NOTE: in the default configura-
       tion this is the	user's password, not the root password).  Once a user
       has been	authenticated, a timestamp is updated and the user may then
       use sudo	without	a password for a short period of time (5 minutes un-
       less overridden in sudoers).

       When invoked as sudoedit, the -e	option (described below), is implied.

       sudo determines who is an authorized user by consulting the file
       /usr/local/etc/sudoers.	By giving sudo the -v flag, a user can update
       the time	stamp without running a	command. The password prompt itself
       will also time out if the user's	password is not	entered	within 5 min-
       utes (unless overridden via sudoers).

       If a user who is	not listed in the sudoers file tries to	run a command
       via sudo, mail is sent to the proper authorities, as defined at config-
       ure time	or in the sudoers file (defaults to root).  Note that the mail
       will not	be sent	if an unauthorized user	tries to run sudo with the -l
       or -v flags.  This allows users to determine for	themselves whether or
       not they	are allowed to use sudo.

       If sudo is run by root and the SUDO_USER	environment variable is	set,
       sudo will use this value	to determine who the actual user is.  This can
       be used by a user to log	commands through sudo even when	a root shell
       has been	invoked.  It also allows the -e	flag to	remain useful even
       when being run via a sudo-run script or program.	 Note however, that
       the sudoers lookup is still done	for root, not the user specified by
       SUDO_USER.

       sudo can	log both successful and	unsuccessful attempts (as well as er-
       rors) to	syslog(3), a log file, or both.	 By default sudo will log via
       syslog(3) but this is changeable	at configure time or via the sudoers
       file.

OPTIONS
       sudo accepts the	following command line options:

       -b  The -b (background) option tells sudo to run	the given command in
	   the background.  Note that if you use the -b	option you cannot use
	   shell job control to	manipulate the process.

       -c  The -c (class) option causes	sudo to	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 sin-
	   gle '-' character.  Specifying a class of - indicates that the com-
	   mand	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	sudo
	   command must	be run from a shell that is already root.  This	option
	   is only available on	systems	with BSD login classes.

       -E  The -E (preserve environment) option	will override the env_reset
	   option in sudoers(5)).  It is only available	when either the	match-
	   ing command has the SETENV tag or the setenv	option is set in sudo-
	   ers(5).

       -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 sudoers file.  If
	   the user is authorized by sudoers 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 VISUAL or EDITOR environment	vari-
	       ables is	run to edit the	temporary files.  If neither VISUAL
	       nor EDITOR are set, the program listed in the editor sudoers
	       variable	is used.

	   3.  If they have been modified, the temporary files are copied back
	       to their	original location and the temporary versions are re-
	       moved.

	   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.

       -H  The -H (HOME) option	sets the HOME environment variable to the
	   homedir of the target user (root by default)	as specified in
	   passwd(5).  By default, sudo	does not modify	HOME (see set_home and
	   always_set_home in sudoers(5)).

       -h  The -h (help) option	causes sudo to print a usage message and exit.

       -i  The -i (simulate initial login) option runs the shell specified in
	   the passwd(5) entry of the user that	the command is being run as.
	   The command name argument given to the shell	begins with a `-' to
	   tell	the shell to run as a login shell.  sudo attempts to change to
	   that	user's home directory before running the shell.	 It also ini-
	   tializes the	environment, leaving TERM unchanged, setting HOME,
	   SHELL, USER,	LOGNAME, and PATH, and unsetting all other environment
	   variables.  Note that because the shell to use is determined	before
	   the sudoers file is parsed, a runas_default setting in sudoers will
	   specify the user to run the shell as	but will not affect which
	   shell is actually run.

       -K  The -K (sure	kill) option is	like -k	except that it removes the
	   user's timestamp entirely.  Like -k,	this option does not require a
	   password.

       -k  The -k (kill) option	to sudo	invalidates the	user's timestamp by
	   setting the time on it to the Epoch.	 The next time sudo is run a
	   password will be required.  This option does	not require a password
	   and was added to allow a user to revoke sudo	permissions from a
	   .logout file.

       -L  The -L (list	defaults) option will list out the parameters that may
	   be set in a Defaults	line along with	a short	description for	each.
	   This	option is useful in conjunction	with grep(1).

       -l  The -l (list) option	will list out the allowed (and forbidden) com-
	   mands for the invoking user on the current host.

       -P  The -P (preserve group vector) option causes	sudo to	preserve the
	   invoking user's group vector	unaltered.  By default,	sudo will ini-
	   tialize 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  The -p (prompt) option allows you to	override the default password
	   prompt and use a custom one.	 The following percent (`%') escapes
	   are supported:

	   %H  expanded	to the local hostname including	the domain name	(on if
	       the machine's hostname is fully qualified or the	fqdn sudoers
	       option is set)

	   %h  expanded	to the local hostname without the domain name

	   %p  expanded	to the user whose password is being asked for (re-
	       spects the rootpw, targetpw and runaspw flags in	sudoers)

	   %U  expanded	to the login name of the user the command will be run
	       as (defaults to root)

	   %u  expanded	to the invoking	user's login name

	   %%  two consecutive % characters are	collapsed into a single	%
	       character

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

       -s  The -s (shell) option runs the shell	specified by the SHELL envi-
	   ronment variable if it is set or the	shell as specified in
	   passwd(5).

       -u  The -u (user) option	causes sudo to run the specified command as a
	   user	other than root.  To specify a uid instead of a	username, use
	   #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  The -V (version) option causes sudo to print	the version number and
	   exit.  If the invoking user is already root the -V option will
	   print out a list of the defaults sudo was compiled with as well as
	   the machine's local network addresses.

       -v  If given the	-v (validate) option, sudo will	update the user's
	   timestamp, prompting	for the	user's password	if necessary.  This
	   extends the sudo timeout for	another	5 minutes (or whatever the
	   timeout is set to in	sudoers) but does not run a command.

       --  The -- flag indicates that sudo should stop processing command line
	   arguments.  It is most useful in conjunction	with the -s flag.

       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_LI-
       BRARY_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 overwise be forbidden.  See
       sudoers(5) for more information.

RETURN VALUES
       Upon successful execution of a program, the return value	from sudo will
       simply be the return value of the program that was executed.

       Otherwise, sudo quits with an exit value	of 1 if	there is a configura-
       tion/permission problem or if sudo cannot execute the given command.
       In the latter case the error string is printed to stderr.  If sudo can-
       not 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 auto-
       mounter 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.

       There are two distinct ways to deal with	environment variables.	By de-
       fault, the env_reset sudoers option is enabled.	This causes commands
       to be executed with a minimal environment containing TERM, PATH,	HOME,
       SHELL, LOGNAME, USER and	USERNAME in addition to	variables from the in-
       voking process permitted	by the env_check and env_keep sudoers options.
       There is	effectively a whitelist	for environment	variables.

       If, however, the	env_reset option is disabled in	sudoers, any variables
       not explicitly denied by	the env_check and env_delete options are in-
       herited from the	invoking process.  In this case, env_check and
       env_delete behave like a	blacklist.  Since it is	not possible to	black-
       list all	potentially dangerous environment variables, use of the	de-
       fault 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 sudo allows 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 se-
       tuid executables, including sudo.  Depending on the operating system
       this may	include	_RLD*, DYLD_*, LD_*, LDR_*, LIBPATH, SHLIB_PATH, and
       others.	These type of variables	are removed from the environment be-
       fore sudo even begins execution and, as such, it	is not possible	for
       sudo to preserve	them.

       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
       environment variable is not modified and	is passed unchanged to the
       program that sudo executes.

       sudo will check the ownership of	its timestamp directory	(/var/run/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 timestamp
       directory is located in a directory writable by anyone (e.g., /tmp), it
       is possible for a user to create	the timestamp directory	before sudo is
       run.  However, because sudo checks the ownership	and mode of the	direc-
       tory and	its contents, the only damage that can be done is to "hide"
       files by	putting	them in	the timestamp dir.  This is unlikely to	happen
       since once the timestamp	dir is owned by	root and inaccessible by any
       other user, the user placing files there	would be unable	to get them
       back out.  To get around	this issue you can use a directory that	is not
       world-writable for the timestamps (/var/adm/sudo	for instance) or cre-
       ate /var/run/sudo with the appropriate owner (root) and permissions
       (0700) in the system startup files.

       sudo will not honor timestamps set far in the future.  Timestamps with
       a date greater than current_time	+ 2 * TIMEOUT will be ignored and sudo
       will log	and complain.  This is done to keep a user from	creating
       his/her own timestamp with a bogus date on systems that allow users to
       give away files.

       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 will not be	logged,	nor will sudo's	access
       control affect them.  The same is true for commands that	offer shell
       escapes (including most editors).  Because of this, care	must be	taken
       when giving users access	to commands via	sudo to	verify that the	com-
       mand does not inadvertently give	the user an effective root shell.  For
       more information, please	see the	PREVENTING SHELL ESCAPES section in
       sudoers(5).

ENVIRONMENT
       sudo utilizes the following environment variables:

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

       HOME	       In -s or	-H mode	(or if sudo was	configured with	the
		       --enable-shell-sets-home	option), set to	homedir	of the
		       target user

       PATH	       Set to a	sane value if the secure_path sudoers option
		       is set.

       SHELL	       Used to determine shell to run with -s option

       SUDO_PROMPT     Used as the default password prompt

       SUDO_COMMAND    Set to the command run by sudo

       SUDO_USER       Set to the login	of the user who	invoked	sudo

       SUDO_UID	       Set to the uid of the user who invoked sudo

       SUDO_GID	       Set to the gid of the user who invoked sudo

       SUDO_PS1	       If set, PS1 will	be set to its value

       USER	       Set to the target user (root unless the -u option is
		       specified)

       VISUAL	       Default editor to use in	-e (sudoedit) mode

FILES
       /usr/local/etc/sudoers  List of who can run what

       /var/run/sudo	       Directory containing timestamps

EXAMPLES
       Note: the following examples assume suitable sudoers(5) entries.

       To get a	file listing of	an unreadable directory:

	$ sudo ls /usr/local/protected

       To list the home	directory of user yazza	on a machine where the file
       system holding ~yazza is	not exported as	root:

	$ sudo -u yazza	ls ~yazza

       To edit the index.html file as user www:

	$ sudo -u www vi ~www/htdocs/index.html

       To shutdown a machine:

	$ sudo shutdown	-r +15 "quick reboot"

       To make a usage listing of the directories in the /home partition.
       Note that this runs the commands	in a sub-shell to make the cd and file
       redirection work.

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

SEE ALSO
       grep(1),	su(1), stat(2),	login_cap(3), passwd(5), sudoers(5), visudo(8)

AUTHORS
       Many people have	worked on sudo over the	years; this version consists
       of code written primarily by:

	       Todd C. Miller
	       Chris Jepeway

       See the HISTORY file in the sudo	distribution or	visit
       http://www.sudo.ws/sudo/history.html for	a short	history	of 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 es-
       capes, thus avoiding sudo's checks.  However, on	most systems it	is
       possible	to prevent shell escapes with sudo's noexec functionality.
       See the sudoers(5) manual for details.

       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.

       If users	have sudo ALL there is nothing to prevent them from creating
       their own program that gives them a root	shell regardless of any	'!'
       elements	in the user specification.

       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://www.sudo.ws/sudo/bugs/

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, in-
       cluding,	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/sudo/license.html for
       complete	details.

1.6.9p17			 Jun 21, 2008			       SUDO(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | RETURN VALUES | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | SEE ALSO | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER

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