Making PostgreSQL backup from standby server

backup_standby.sh

# 1. Pause replication

sudo -u postgres psql -c 'SELECT pg_xlog_replay_pause();'

# 2. Perform backup

sudo -u postgres pg_dump -Fc DBNAME > /path/to/backup

#3. Resume replication

sudo -u postgres psql -c 'SELECT pg_xlog_replay_resume();'

#Keep in mind that running above commands will cause recovery lag on the slave, which might be quite large, depending on you database size. Also, take into account the space WAL segments will take, as they will not be replayed on slave during the pause.