problem backup/restore PSQL DB

Hi all,
I am trying to backup a psql database in one system(Debian), and restore
it to another system(ubuntu) which has a fresh installed psql db. However,
I got the following errors. Can anyone give me some help on solving it. Many
thanks.

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OME Restore
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\_ Extracting postgres database ome and checking archive version
/bin/tar --preserve-permissions --same-owner --directory /tmp -xf
'ome_backup_2006-07-24.tar' OMEmaint omeDB_backup \_ Checking archive for
OMEIS files
/bin/tar -tf 'ome_backup_2006-07-24.tar' Files/lastFileID
\_ Restoring postgress database ome
Checking database
Database ome (version 2.23) was found and it will be overwritten. Continue
? [y/n]: y
su postgres -c '/usr/bin/createuser --adduser --createdb ome'
createuser: creation of new user failed: ERROR: user "ome" already exists
su postgres -c '/usr/bin/createdb -T template0 ome'
CREATE DATABASE
su postgres -c '/usr/bin/pg_restore -O -d ome
--use-set-session-authorization /tmp/omeDB_backup'
pg_restore: [archiver (db)] could not execute query: ERROR: user "rajesh"
does not exist