After updating 11.04 to 11.10 using 'do-release-upgrade', installer did not updated PostgreSQL 8.4 to 9 version, saying that i have to do it manually. But how? I heard many problems, for example data loss, or dissapered config files after updating manually from 8.4 to 9 in Ubuntu. Sow how to update, to avoid data damage or other problems? Thanks.
Start by making a backup of your database, worse case scenerio I would hope you could re-install 11.04 and restore postgresql from backup. You may need to re-install postgresql 8.4 first.
Stop postgresql and any services that use it (apache ?)
su - postgres pg_dumpall >backup_db exit
Save a copy of
backup_db to 2 safe locations, /root and a flash drive.
Now purge 8.4 and install 9.0
apt-get purge postgresql-8.4 apt-get install postgresql-9.0
Now restore your data
su - postgres psql <backup_db exit
Restart postgresql and your other services, check your data.
Good luck =)