"Ed L." <pgsql@bluepolka.net> writes:
> Killed the stuck postmaster with sigkill, edited the file,
> restarted postmaster, and it re-wrote the file with the bogus
> entry. I don't have any superuser sessions open. Is there
> another route?
What you're going to need to do is stop the postmaster, start
a standalone backend (see the "postgres" man page entry if you
never did that before) and issue the ALTER USER in the standalone
backend. Then you can restart normal operations.
regards, tom lane