visudo

edit the sudoers file

References

Synopsis

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

visudo edits the sudoers file in a safe fashion, analogous to vipw.
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.

-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.
-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.
……

visudo

After using visudo to grant all privileges to a new user :

$ sudo vim /etc/hosts
sudo: must be setuid root

Solution

Getting message sudo: must be setuid root, but sudo IS already owned by root - Stack Overflow : https://stackoverflow.com/a/16682298

$ su root
$ chmod u+s /usr/bin/sudo
$ su non_root_user
# then test