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SUDO(8)                      MAINTENANCE COMMANDS                      SUDO(8)

       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 (15 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
       /etc/sudoers.  By giving sudo the -v flag a user can update the time
       stamp without running a command. The password prompt itself will not
       time out in Debian's version (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 15 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, CDPATH, ENV, BASH_ENV, KRB_CONF, KRB-
       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.  Environment
       variables with a value beginning with () are also removed as they could
       be interpreted as bash functions.  If sudo has been compiled 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 con-
       tained 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

        /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
       http://www.sudo.ws/sudo/history.html 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
       http://www.sudo.ws/sudo/support.html for details.

       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.

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

1.6.8p7                        February 5, 2005                        SUDO(8)