visudo(8) - phpMan

VISUDO(8)                              MAINTENANCE COMMANDS                             VISUDO(8)


NAME
       visudo - edit the sudoers file

SYNOPSIS
       visudo [-c] [-q] [-s] [-V] [-f sudoers]

DESCRIPTION
       visudo edits the sudoers file in a safe fashion, analogous to vipw(8).  visudo locks the
       sudoers file against multiple simultaneous edits, provides basic sanity checks, and checks
       for parse errors.  If the sudoers file is currently being edited you will receive a mes-
       sage to try again later.

       There is a hard-coded list of editors that visudo will use set at compile-time that may be
       overridden via the editor sudoers Default variable.  On Debian systems, this list defaults
       to /usr/bin/editor, which is meant to be a system-wide default editor chosen through the
       alternatives system.  Normally, visudo does not honor the VISUAL or EDITOR environment
       variables unless they contain an editor in the aforementioned editors list.  However, if
       visudo is configured with the --with-enveditor flag or the env_editor Default variable is
       set in sudoers, visudo will use any the editor defines by VISUAL or EDITOR.  Note that
       this can be a security hole since it allows the user to execute any program they wish sim-
       ply by setting VISUAL or EDITOR.  Despite this potential risk, sudo on Debian is compiled
       with the --with-enveditor flag.

       visudo parses the sudoers file after the edit and will not save the changes if there is a
       syntax error.  Upon finding an error, visudo will print a message stating the line num-
       ber(s) where the error occurred and the user will receive the "What now?" prompt.  At this
       point the user may enter "e" to re-edit the sudoers file, "x" to exit without saving the
       changes, or "Q" to quit and save changes.  The "Q" option should be used with extreme care
       because if visudo believes there to be a parse error, so will sudo and no one will be able
       to sudo again until the error is fixed.  If "e" is typed to edit the  sudoers file after a
       parse error has been detected, the cursor will be placed on the line where the error
       occurred (if the editor supports this feature).

OPTIONS
       visudo accepts the following command line options:

       -c  Enable check-only mode.  The existing sudoers file will be checked for syntax and a
           message will be printed to the standard output detailing the status of sudoers.  If
           the syntax check completes successfully, visudo will exit with a value of 0.  If a
           syntax error is encountered, visudo will exit with a value of 1.

       -f  Specify and alternate sudoers file location.  With this option visudo will edit (or
           check) the sudoers file of your choice, instead of the default, /etc/sudoers.  The
           lock file used is the specified sudoers file with ".tmp" appended to it.

       -q  Enable quiet mode.  In this mode details about syntax errors are not printed.  This
           option is only useful when combined with the -c flag.

       -s  Enable strict checking of the sudoers file.  If an alias is used before it is defined,
           visudo will consider this a parse error.  Note that it is not possible to differenti-
           ate between an alias and a hostname or username that consists solely of uppercase let-
           ters, digits, and the underscore ('_') character.

       -V  The -V (version) option causes visudo to print its version number and exit.

ENVIRONMENT
       The following environment variables are used only if visudo was configured with the
       --with-env-editor option:

       VISUAL          Invoked by visudo as the editor to use

       EDITOR          Used by visudo if VISUAL is not set

FILES
       /etc/sudoers            List of who can run what

       /etc/sudoers.tmp        Lock file for visudo

DIAGNOSTICS
       sudoers file busy, try again later.
           Someone else is currently editing the sudoers file.

       /etc/sudoers.tmp: Permission denied
           You didn't run visudo as root.

       Can't find you in the passwd database
           Your userid does not appear in the system passwd file.

       Warning: undeclared Alias referenced near ...
           Either you are using a {User,Runas,Host,Cmnd}_Alias before defining it or you have a
           user or hostname listed that consists solely of uppercase letters, digits, and the
           underscore ('_') character.  If the latter, you can ignore the warnings (sudo will not
           complain).  In -s (strict) mode these are errors, not warnings.

       Warning: runas_default set after old value is in use ...
           You have a runas_default Defaults setting listed in the sudoers file after its value
           has already been used.  This means that entries prior to the runas_default setting
           will match based on the default value of runas_default (root) whereas entries after
           the runas_default setting will match based on the new value.  This is usually uninten-
           tional and in most cases the <runas_default> setting should be placed before any
           Runas_Alias or User specifications.  In -s (strict) mode this is an error, not a warn-
           ing.

SEE ALSO
       vi(1), sudoers(5), sudo(8), vipw(8)

AUTHOR
       Many people have worked on sudo over the years; this version of visudo was written by:

        Todd Miller

       See the HISTORY file in the sudo distribution or visit http://www.sudo.ws/sudo/his-
       tory.html for more details.

CAVEATS
       There is no easy way to prevent a user from gaining a root shell if the editor used by
       visudo allows shell escapes.

BUGS
       If you feel you have found a bug in visudo, 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
       visudo is provided ``AS IS'' and any express or implied warranties, including, 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                                 VISUDO(8)