I've lost sudo access and I don't really understand why

[Colin Law]

On Thu, 19 Mar 2020 at 12:17, Chris Green <cl at isbd.net> wrote:
> ...
> Yes, dead simple, it took only a minute or so.  Reboot, hit ESC,
> select recovery mode and then 'drop to root prompt'.  Do the required
> usermod command, restart and all is well again.

You may well find various other things don't work because you have
removed those groups to, so you may have to add them back as you find
them.  To save hassle it might be a good idea to create a new user
with admin permissions and then look at what groups that is in, and
then add them to yourself too.  Otherwise you may find in six months
time that something you use only rarely does not work and you won't
necessarily think of the missing group problem.

Colin