Linux

I've managed to screw up my sudoers file (using sudo visudo) and can't fix it.

Any attempt to move it or edit it or whatever gives me Permission denied.

Any attempt to move it or edit it or whatever using sudo gives me

sudo: parse error in /etc/sudoers near line 28
sudo: no valid sudoers sources found, quitting...
sudo: unable to initialise policy plug-in

Also tried using pkexec which seems to be the common suggestion, it gives me:

polkit-agent-helper-1: error response to PolicyKit daemon: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: No session for cookie
==== AUTHENTICATION FAILED ===
Error executing command as another user: Not authorized

Any suggestions. It seems a fairly circular flaw.