MirOS Manual: sudo(8), sudoedit(8)


SUDO(8)               MAINTENANCE COMMANDS                SUDO(8)

NAME

     sudo, sudoedit - execute a command as another user

SYNOPSIS

     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 [...]

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
     password is required.  Otherwise, sudo requires that users
     authenticate themselves with a password by default (NOTE: in
     the default configuration 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 /etc/sudoers.  By giving sudo the -v flag a user can
     update the time stamp without running a command. The pass-
     word prompt itself will also time out if the user's password
     is not entered within 5 minutes (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 configure 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 vari-
     able 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

1.6.8p9                   June 20, 2005                         1

SUDO(8)               MAINTENANCE COMMANDS                SUDO(8)

     sudoers lookup is still done for root, not the user speci-
     fied by SUDO_USER.

     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 sudoers file.

OPTIONS

     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 password.

     -L  The -L (list defaults) option will list out the parame-
         ters 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 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 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 specified 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 sys-
         tems 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

1.6.8p9                   June 20, 2005                         2

SUDO(8)               MAINTENANCE COMMANDS                SUDO(8)

         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 single '-' character.
         Specifying a class of - indicates that the command
         should be run restricted by the default login capabili-
         ties 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 tem-
                 porary 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 file.

     -h  The -h (help) option causes sudo to print a usage mes-
         sage 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

1.6.8p9                   June 20, 2005                         3

SUDO(8)               MAINTENANCE COMMANDS                SUDO(8)

         user's home directory before running the shell.  It also
         initializes the environment, leaving TERM unchanged,
         setting HOME, SHELL, USER, LOGNAME, and PATH, and unset-
         ting 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 for-
         bidden) commands 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 fol-
         lowing percent (`%') escapes are supported:

         %u      expanded to the invoking user's login name

         %U      expanded to the login name of the user the com-
                 mand 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 % character

     -s  The -s (shell) option runs the shell specified by the
         SHELL environment 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.  Note that if the tar-
         getpw Defaults option is set (see sudoers(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

1.6.8p9                   June 20, 2005                         4

SUDO(8)               MAINTENANCE COMMANDS                SUDO(8)

         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 conjunc-
         tion 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
     configuration/permission problem or if sudo cannot execute
     the given command.  In the latter case the error string is
     printed to stderr.  If sudo cannot 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 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.
     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,
     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.
     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 contained in
     the output of sudo -V when run as root.

     To prevent command spoofing, sudo checks "." and "" (both
     denoting current directory) last when searching for a com-
     mand 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.

1.6.8p9                   June 20, 2005                         5

SUDO(8)               MAINTENANCE COMMANDS                SUDO(8)

     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 con-
     tents 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 direc-
     tory 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. Times-
     tamps 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 expli-
     citly 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 (includ-
     ing 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.

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

1.6.8p9                   June 20, 2005                         6

SUDO(8)               MAINTENANCE COMMANDS                SUDO(8)

      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

      /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 par-
     tition.  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), sudoers(5),

1.6.8p9                   June 20, 2005                         7

SUDO(8)               MAINTENANCE COMMANDS                SUDO(8)

     passwd(5), visudo(8)

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.

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 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).

BUGS

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

SUPPORT

     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.

1.6.8p9                   June 20, 2005                         8

SUDO(8)               MAINTENANCE COMMANDS                SUDO(8)

DISCLAIMER

     Sudo is provided ``AS IS'' and any express or implied war-
     ranties, including, but not limited to, the implied warran-
     ties 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.

1.6.8p9                   June 20, 2005                         9

Generated on 2014-07-04 21:17:45 by $MirOS: src/scripts/roff2htm,v 1.79 2014/02/10 00:36:11 tg Exp $

These manual pages and other documentation are copyrighted by their respective writers; their source is available at our CVSweb, AnonCVS, and other mirrors. The rest is Copyright © 2002‒2014 The MirOS Project, Germany.
This product includes material provided by Thorsten Glaser.

This manual page’s HTML representation is supposed to be valid XHTML/1.1; if not, please send a bug report – diffs preferred.