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 didnt run visudo as root.
Cant 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 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.
1.6.8p12 June 20, 2005 VISUDO(8)
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