You can create /etc/nologin
to restrict users from login into the system. Only root login will be allowed then.
--- Adding -------
Perhaps I didn't read your question properly & I thought you want to restrict users from login into system.
Anyway, you can use /sbin/nologin
shell to restrict user, but check whether this is available in your system or not.
If it's not available, then you can add /bin/false
as shell for the user whom you do not wish to give login access.
usermod -s /sbin/nologin username
usermod -s /bin/false username
In addition to /bin/false
, add /dev/null
in place of home directory in /etc/passwd
. (Note: Take backup of /etc/passwd if you manually edit it). New /etc/passwd file entry for that user will look like this: