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       sudo, sudoedit -	execute	a command as another user

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

       sudo [-HPSb] [-a	auth_type] [-c class|-]	[-p prompt] [-u	username|#uid]
       {-e file	[...] |	-i | -s	| command}

       sudoedit	[-S] [-a auth_type] [-p	prompt]	[-u username|#uid] file	[...]

       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
       unless 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 can	log both successful and	unsuccessful attempts (as well as
       errors) 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 sudo-
       ers file.

       sudo accepts the	following command line options:

       -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)).

       -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

       -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).

       -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.

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

       -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.

       -a  The -a (authentication type)	option causes sudo to use the speci-
	   fied	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 where sudo has been configured with the
	   --with-bsdauth option.

       -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 where sudo has
	   been	configured with	the --with-logincap option.

       -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
		   variables 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 removed.

	   If the specified file does not exist, it will be created.  Note
	   that	unlike most commands run by sudo, the editor is	run with the
	   invoking user's environment unmodified.  If,	for some reason, sudo
	   is unable to	update a file with its edited version, the user	will
	   receive a warning and the edited copy will remain in	a temporary

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

       -p  The -p (prompt) option allows you to	override the default password
	   prompt and use a custom one.	 The following percent (`%') escapes
	   are supported:

	   %u	   expanded to the invoking user's login name

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

	   %h	   expanded to the local hostname without the domain name

	   %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)

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

       -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

       -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.  Note that if the targetpw Defaults option is set (see	sudo-
	   ers(5)) it is not possible to run commands with a uid not listed in
	   the password	database.

       -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.

       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.

       sudo tries to be	safe when executing external commands.	Variables that
       control how dynamic loading and binding is done can be used to subvert
       the program that	sudo runs.  To combat this the LD_*, _RLD_*,
       SHLIB_PATH (HP-UX only),	and LIBPATH (AIX only) environment variables
       are removed from	the environment	passed on to all commands executed.
       sudo will also remove the IFS, ENV, BASH_ENV, KRB_CONF, KRBCONFDIR,
       PATH_LOCALE, TERMINFO, TERMINFO_DIRS and	TERMPATH variables as they too
       can pose	a threat.  If the TERMCAP variable is set and is a pathname,
       it too is ignored.  Additionally, if the	LC_* or	LANGUAGE variables
       contain the / or	% characters, they are ignored.	 If sudo has been com-
       piled with SecurID support, the VAR_ACE,	USR_ACE	and DLC_ACE variables
       are cleared as well.  The list of environment variables that sudo
       clears is contained in the output of sudo -V when run as	root.

       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.

       For security reasons, if	your OS	supports shared	libraries and does not
       disable user-defined library search paths for setuid programs (most
       do), you	should either use a linker option that disables	this behavior
       or link sudo statically.

       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 and	only writable by 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 directory 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 create
       /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 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 command
       does not	inadvertently give the user an effective root shell.

       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 sudo was configured with
			       the --with-secure-path option

	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

	/usr/local/etc/sudoers		 List of who can run what
	/var/run/sudo		   Directory containing	timestamps

       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"

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

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

	       Todd Miller
	       Chris Jepeway

       See the HISTORY file in the sudo	distribution or	visit for	a short	history	of sudo.

       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 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 whe 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).

       If you feel you have found a bug	in sudo, please	submit a bug report at

       Commercial support is available for sudo, see for	details.

       Limited free support is available via the sudo-users mailing list, see to subscribe or search
       the archives.

       Sudo is provided	``AS IS'' and any express or implied warranties,
       including, but not limited to, the implied warranties of	merchantabil-
       ity and fitness for a particular	purpose	are disclaimed.	 See the
       LICENSE file distributed	with sudo or for	complete details.

1.6.8			      September	 8, 2004		       SUDO(8)


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