.\"
.\" Copyright (c) 1996,1998-2005, 2007-2013
.\"	Todd C. Miller <Todd.Miller@courtesan.com>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" Sponsored in part by the Defense Advanced Research Projects
.\" Agency (DARPA) and Air Force Research Laboratory, Air Force
.\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
.\"
.Dd December 16, 2013
.Dt VISUDO 8
.Os Sudo 1.8.9p5
.Sh NAME
.Nm visudo
.Nd edit the sudoers file
.Sh SYNOPSIS
.Nm visudo
.Op Fl chqsV
.Bk -words
.Op Fl f Ar sudoers
.Ek
.Bk -words
.Op Fl x Ar file
.Ek
.Sh DESCRIPTION
.Nm visudo
edits the
.Em sudoers
file in a safe fashion, analogous to
.Xr vipw 8 .
.Nm visudo
locks the
.Em sudoers
file against multiple simultaneous edits, provides basic sanity checks,
and checks for parse errors.
If the
.Em sudoers
file is currently being edited you will receive a message to try again later.
.Pp
There is a hard-coded list of one or more editors that
.Nm visudo
will use set at compile-time that may be overridden via the
.Em editor
.Em sudoers
.Li Default
variable.
This list defaults to
.Li "/usr/local/bin/vi" .
Normally,
.Nm visudo
does not honor the
.Ev VISUAL
or
.Ev EDITOR
environment variables unless they contain an editor in the aforementioned
editors list.
However, if
.Nm visudo
is configured with the
.Li --with-env-editor
option or the
.Em env_editor
.Li Default
variable is set in
.Em sudoers ,
.Nm visudo
will use any the editor defines by
.Ev VISUAL
or
.Ev EDITOR .
Note that this can be a security hole since it allows the user to
execute any program they wish simply by setting
.Ev VISUAL
or
.Ev EDITOR .
.Pp
.Nm visudo
parses the
.Em sudoers
file after the edit and will
not save the changes if there is a syntax error.
Upon finding an error,
.Nm visudo
will print a message stating the line number(s)
where the error occurred and the user will receive the
.Dq What now?
prompt.
At this point the user may enter
.Ql e
to re-edit the
.Em sudoers
file,
.Ql x
to exit without saving the changes, or
.Ql Q
to quit and save changes.
The
.Ql Q
option should be used with extreme care because if
.Nm visudo
believes there to be a parse error, so will
.Nm sudo
and no one
will be able to
.Nm sudo
again until the error is fixed.
If
.Ql e
is typed to edit the
.Em 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).
.Pp
The options are as follows:
.Bl -tag -width Fl
.It Fl c , -check
Enable
.Em check-only
mode.
The existing
.Em sudoers
file will be
checked for syntax errors, owner and mode.
A message will be printed to the standard output describing the status of
.Em sudoers
unless the
.Fl q
option was specified.
If the check completes successfully,
.Nm visudo
will exit with a value of 0.
If an error is encountered,
.Nm visudo
will exit with a value of 1.
.It Fl f Ar sudoers , Fl -file Ns No = Ns Ar sudoers
Specify an alternate
.Em sudoers
file location.
With this option,
.Nm visudo
will edit (or check) the
.Em sudoers
file of your choice,
instead of the default,
.Pa /etc/sudoers .
The lock file used is the specified
.Em sudoers
file with
.Dq \.tmp
appended to it.
In
.Em check-only
mode only, the argument to
.Fl f
may be
.Ql - ,
indicating that
.Em sudoers
will be read from the standard input.
.It Fl h , -help
Display a short help message to the standard output and exit.
.It Fl q , -quiet
Enable
.Em quiet
mode.
In this mode details about syntax errors are not printed.
This option is only useful when combined with
the
.Fl c
option.
.It Fl s , -strict
Enable
.Em strict
checking of the
.Em sudoers
file.
If an alias is used before it is defined,
.Nm 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
.Pq Ql _
character.
.It Fl V , -version
Print the
.Nm visudo
and
.Em sudoers
grammar versions and exit.
.It Fl x Ar file , Fl -export Ns No = Ns Ar file
Export
.Em sudoers
in JSON format and write it to
.Ar file .
If
.Ar file
is
.Ql - ,
the exported
.Em sudoers
policy will to be written to the standard output.
The exported format is intended to be easier for third-party
applications to parse that the traditional
.Em sudoers
format.
The various values have explicit types which removes much of the
ambiguity of the
.Em sudoers
format.
.El
.Sh ENVIRONMENT
The following environment variables may be consulted depending on
the value of the
.Em editor
and
.Em env_editor
.Em sudoers
settings:
.Bl -tag -width 15n
.It Ev VISUAL
Invoked by
.Nm visudo
as the editor to use
.It Ev EDITOR
Used by
.Nm visudo
if
.Ev VISUAL
is not set
.El
.Sh FILES
.Bl -tag -width 24n
.It Pa /etc/sudoers
List of who can run what
.It Pa /etc/sudoers.tmp
Lock file for visudo
.El
.Sh DIAGNOSTICS
.Bl -tag -width 4n
.It Li sudoers file busy, try again later.
Someone else is currently editing the
.Em sudoers
file.
.It Li /etc/sudoers.tmp: Permission denied
You didn't run
.Nm visudo
as root.
.It Li Can't find you in the passwd database
Your user ID does not appear in the system passwd file.
.It Li 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
.Pq Ql _
character.
In the latter case, you can ignore the warnings
.Po
.Nm sudo
will not complain
.Pc .
In
.Fl s
(strict) mode these are errors, not warnings.
.It Li 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.
In
.Fl s
(strict) mode this is an error, not a warning.
.It Li 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
.Nm sudo
will ignore cycles when parsing
the
.Em sudoers
file.
.El
.Sh SEE ALSO
.Xr vi 1 ,
.Xr sudoers 5 ,
.Xr sudo 8 ,
.Xr vipw 8
.Sh AUTHORS
Many people have worked on
.Nm sudo
over the years; this version consists of code written primarily by:
.Bd -ragged -offset indent
Todd C. Miller
.Ed
.Pp
See the CONTRIBUTORS file in the
.Nm sudo
distribution (http://www.sudo.ws/sudo/contributors.html) for an
exhaustive list of people who have contributed to
.Nm sudo .
.Sh CAVEATS
There is no easy way to prevent a user from gaining a root shell if
the editor used by
.Nm visudo
allows shell escapes.
.Sh BUGS
If you feel you have found a bug in
.Nm visudo ,
please submit a bug report at http://www.sudo.ws/sudo/bugs/
.Sh 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.
.Sh DISCLAIMER
.Nm visudo
is provided
.Dq 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
.Nm sudo
or http://www.sudo.ws/sudo/license.html for complete details.
