visudo(8)


NAME

     visudo --- edit the sudoers file

SYNOPSIS

     visudo [-chqsV] [-f sudoers] [-x output_file]

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 message to try
     again later.

     There is a hard-coded list of one or more editors that visudo will use
     set at compile-time that may be overridden via the editor sudoers Default
     variable.  This list defaults to /usr/bin/editor.  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-env-editor option 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 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 run 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).

     The options are as follows:

     -c, --check
             Enable check-only mode.  The existing sudoers file will be
             checked for syntax errors, owner and mode.  A message will be
             printed to the standard output describing the status of
             sudoers unless the -q option was specified.  If the check
             completes successfully, visudo will exit with a value of 0.
             If an error is encountered, visudo will exit with a value of
             1.

     -f sudoers, --file=sudoers
             Specify an 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.  In check-only mode only, the argument to -f may be '-',
             indicating that sudoers will be read from the standard input.

     -h, --help  Display a short help message to the standard output and exit.

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

     -s, --strict
             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 host name or user name that consists solely of
             uppercase letters, digits, and the underscore ('_')
             character.

     -V, --version
             Print the visudo and sudoers grammar versions and exit.

     -x output_file, --export=output_file
             Export a sudoers in JSON format and write it to output_file.
             If output_file is '-', the exported sudoers policy will be
             written to the standard output.  By default, /etc/sudoers
             (and any files it includes) will be exported.  The -f option
             can be used to specify a different sudoers file to export.
             The exported format is intended to be easier for third-party
             applications to parse than the traditional sudoers format.
             The various values have explicit types which removes much of
             the ambiguity of the sudoers format.

   Debugging and sudoers plugin arguments
     visudo versions 1.8.4 and higher support a flexible debugging framework
     that is configured via Debug lines in the sudo.conf(5) file.

     Starting with sudo 1.8.12, visudo will also parse the arguments to the
     sudoers plugin to override the default sudoers path name, UID, GID and
     file mode.  These arguments, if present, should be listed after the path
     to the plugin (i.e. after sudoers.so).  Multiple arguments may be
     specified, separated by white space.  For example:

       Plugin sudoers_policy sudoers.so sudoers_mode=0400

     The following arguments are supported:

     sudoers_file=pathname
           The sudoers_file argument can be used to override the default
           path to the sudoers file.

     sudoers_uid=uid
           The sudoers_uid argument can be used to override the default
           owner of the sudoers file.  It should be specified as a numeric
           user ID.

     sudoers_gid=gid
           The sudoers_gid argument can be used to override the default
           group of the sudoers file.  It must be specified as a numeric
           group ID (not a group name).

     sudoers_mode=mode
           The sudoers_mode argument can be used to override the default
           file mode for the sudoers file.  It should be specified as an
           octal value.

     For more information on configuring sudo.conf(5), please refer to its
     manual.

ENVIRONMENT

     The following environment variables may be consulted depending on the
     value of the editor and env_editor sudoers settings:

     VISUAL           Invoked by visudo as the editor to use

     EDITOR           Used by visudo if VISUAL is not set

FILES

     /etc/sudo.conf            Sudo front end configuration

     /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 user ID does not appear in the system passwd file.

     Warning: {User,Runas,Host,Cmnd}_Alias referenced but not defined
       Either you are trying to use an undeclared
       {User,Runas,Host,Cmnd}_Alias or you have a user or host name listed
       that consists solely of uppercase letters, digits, and the
       underscore ('_') character.  In the latter case, you can ignore the
       warnings (sudo will not complain).  In -s (strict) mode these are
       errors, not warnings.

     Warning: unused {User,Runas,Host,Cmnd}_Alias
       The specified {User,Runas,Host,Cmnd}_Alias was defined but never
       used.  You may wish to comment out or remove the unused alias.

     Warning: cycle in {User,Runas,Host,Cmnd}_Alias
       The specified {User,Runas,Host,Cmnd}_Alias includes a reference to
       itself, either directly or through an alias it includes.  This is
       only a warning by default as sudo will ignore cycles when parsing
       the sudoers file.

     visudo: /etc/sudoers: input and output files must be different
       The -x flag was used and the specified output_file has the same
       path name as the sudoers file to export.

SEE ALSO

     vi(1), sudo.conf(5), sudoers(5), sudo(8), vipw(8)

AUTHORS

     Many people have worked on sudo over the years; this version consists of
     code written primarily by:

       Todd C. Miller

     See the CONTRIBUTORS file in the sudo distribution
     (https://www.sudo.ws/contributors.html) for an exhaustive list of people
     who have contributed to sudo.

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
     https://bugzilla.sudo.ws/

SUPPORT

     Limited free support is available via the sudo-users mailing list, see
     https://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 https://www.sudo.ws/license.html for
     complete details.





Opportunity


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.





Free Software


Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.


Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.





Free Books


The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.


Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.





Education


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.


Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.