Getting dump from old version

Hi!

I use postgres6.1. Before install new version I do not make dump_all, but
I move /usr/local/pgsql to /usr/local/pgsql_bk. After that I successfuly
install new version to /usr/local/pgsql. But now I need some data from old
postgres. I try to do this:
% kill postmaster_id
% mv /usr/local/pgsql /usr/local/pgsql-7.4
% mv /usr/local/pgsql_bk /usr/local/pgsql
% su -l pgsql -c 'exec
/usr/local/pgsql/bin/postmaster -D/usr/local/pgsql/data -S -o -F -d 3 >&
/usr/local/pgsql/errlog' &
% ps axu | grep postmaster show me postmaster process running:
postgres 14442 ?? Is 0:00.00
/usr/local/pgsql/bin/postmaster -D/usr/local/pgsql/data -S -o -F -d 3
(postgres)

I try to exec pg_dumpall as postgres user:
./pg_dumpall
Connection to database 'template1' failed.
PQexec() -- Request was sent to backend, but backend closed the channel
before r
esponding. This probably means the backend terminated abnormally before or
whil
e processing the request.
......

I try to connect as postgres user:
% /usr/local/pgsql/bin/psql
Connection to database 'postgres' failed.
FATAL 1:Database postgres does not exist in pg_database

% ls -al /usr/local/pgsql/data/base
drwxr-xr-x 2 postgres postgres 1024 Apr 2 2000 postgres
drwx------ 2 postgres postgres 1024 Apr 1 2000 template1
[ .. some other bases .. ]

Could someone help me? I need to get dump from old DB.

Thanks.