visudo - edit the sudoers file
SYNOPSIS
visudo [ -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, 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. In the default configuration, the vi(1)
editor is used, but there is a compile time option to
allow use of whatever editor the environment variables
EDITOR or VISUAL are set to.
visudo parses the sudoers file after the edit and will not
save the changes if there is a syntax error. Upon finding
an error, a message will be printed stating the line
number(s) that the error occurred on and the user will
receive the "What now?" prompt. At this point the user
may enter "e" to re-edit the sudoers file, enter "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 execute sudo again
until the error is fixed. Any other command at this
prompt will print a short help message. When editing 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 option:
-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 upper
case letters, digits, and the underscore ('_')
character.
-V The -V (version) option causes visudo to print the
version number and exit.
ERRORS
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.
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 upper case 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.
ENVIRONMENT
The following environment variables are used only if
visudo was configured with the --with-env-editor option:
EDITOR Used by visudo as the editor to use
VISUAL Used by visudo if EDITOR is not set
FILES
/etc/sudoers List of who can run what
/etc/sudoers.tmp Lock file for visudo
AUTHOR
Many people have worked on sudo over the years, this
version of visudo was written by:
Todd Miller <Todd.Miller@courtesan.com>
See the HISTORY file in the sudo distribution for more
details.
BUGS
If you feel you have found a bug in sudo, please submit a
bug report at http://www.courtesan.com/sudo/bugs/
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 for complete 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.
SEE ALSO
sudo(8), vipw(8).
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