visudo



VISUDO(8)                    MAINTENANCE COMMANDS                    VISUDO(8)




NAME

       visudo - edit the sudoers file


SYNOPSIS

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


DESCRIPTION

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

       There is a hard-coded list of editors that visudo will use set at com-
       pile-time that may be overridden via the editor sudoers Default vari-
       able.  This list defaults to the path to vi(1) on your system, as
       determined by the configure script.  Normally, visudo does not honor
       the VISUAL or EDITOR environment variables unless they contain an edi-
       tor in the aforementioned editors list.  However, if visudo is config-
       ured with the --with-enveditor flag or the enveditor 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 simply by setting VISUAL or EDITOR.

       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 number(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 differentiate between an alias and
           a hostname or username that consists solely of uppercase letters,
           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 config-
       ured 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 unintentional 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 warning.


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/history.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

       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.


DISCLAIMER

       Visudo 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.



1.6.8p8                         March 12, 2005                       VISUDO(8)

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