Solution for psql: FATAL: Peer authentication failed for user "postgres" - arrivu/beacon GitHub Wiki
if we get this following error while using su -U postgres
psql: FATAL: Peer authentication failed for user "postgres"
For avoiding this error we need to edit the below file and change the permission to the localhost in line number 59
# vim /var/lib/pgsql/9.3/data/postgresql.conf
Then Edit the file pg_hba.conf and change the ident to trust in line number 80 & 82
# vim /var/lib/pgsql/9.3/data/pg_hba.conf
Then restart the postgresql service to take effect the modification
# /etc/init.d/postgresql-9.3 restart