s anwar <sanwar(at)gmail(dot)com> writes:
> I have a postgres 8.1 database running under FC4 x86_64. While I was
> clustering a table, the machine died (kernel/hardware issue). When I
> restarted the machine, the space used by postgres during the cluster
> operation was still in use.
That would be in the form of a file that's not referenced by any value
of pg_class.relfilenode. I think you have to find and delete the file
by hand --- there is not any automated mechanism for this. See
http://www.postgresql.org/docs/8.1/static/storage.html
regards, tom lane