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SUDO(8)			     MAINTENANCE COMMANDS		       SUDO(8)

NAME
       sudo - execute a	command	as another user

SYNOPSIS
       sudo  -V	| -h | -l | -L | -v | -k | -K |	-s | [ -H ] [-P	] [-S ]	[ -b ]
       | [ -p prompt ] [ -c class|- ] [	-a auth_type ] [  -u  username|#uid  ]
       command

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 (the group vector is also initialized when the	target
       user is not root).  By default, sudo requires that  users  authenticate
       themselves  with	 a password (NOTE: by default this is the user's pass-
       word, 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).

       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  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.

       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:

       -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.

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

       -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).

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

       -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.

       -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.

       -K  The -K (sure	kill) option to	sudo removes the user's	timestamp  en-
	   tirely.  Likewise, this option does not require a password.

       -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.

       -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 collaped into a  single  %
		   character

       -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.

       -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.

       -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.

       -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).

       -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.

       -P  The -P (preserve group vector) option causes	sudo to	 preserve  the
	   user's  group  vector  unaltered.  By default, sudo will initialize
	   the group vector to the list	of groups the target user is in.   The
	   real	 and  effective	group IDs, however, are	still set to match the
	   target user.

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

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

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.	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,
       KRBTKFILE, KRB5_CONFIG, LOCALDOMAIN, RES_OPTIONS, HOSTALIASES, NLSPATH,
       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.

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
       filesystem 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"

ENVIRONMENT
       sudo utilizes the following environment variables:

	PATH		       Set to a	sane value if SECURE_PATH is set
	SHELL		       Used to determine shell to run with -s option
	USER		       Set to the target user (root unless the -u option
			       is specified)
	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.
	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

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

AUTHORS
       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
       http://www.sudo.ws/sudo/history.html for	a short	history	of sudo.

BUGS
       If you feel you have found a bug	in sudo, please	submit a bug report at
       http://www.sudo.ws/sudo/bugs/

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 for complete details.

CAVEATS
       There  is  no  easy  way	to prevent a user from gaining a root shell if
       that user has access to commands	allowing shell escapes.

       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
       supports	the /dev/fd/ directory,	setuid	shell  scripts	are  generally
       safe).

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

1.6.7				March 13, 2003			       SUDO(8)

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

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