When installing PostgreSQL 9.1 through Debian Backports, you'll notice a key difference from the standard installation path. Instead of the traditional /etc/postgresql/9.1/ directory structure, the backports package uses a more modern approach with /etc/postgresql-common/.

The Debian PostgreSQL maintainers changed the configuration directory structure in newer versions to better handle multiple PostgreSQL instances. The postgresql-common package now centralizes configuration management. This is actually an improvement, though it might be confusing coming from older installations.

Your main configuration files are now located in:

/etc/postgresql-common/
|-- pg_createcluster.conf
|-- pg_ctl.conf
|-- postgresql.conf
|-- user_clusters

For cluster-specific configurations (equivalent to the old 9.1 directory), check:

/etc/postgresql/<version>/<cluster_name>/

First, verify your PostgreSQL installation is complete and running:

sudo service postgresql status
pg_lsclusters

If you need the traditional directory structure, you can create a new cluster:

sudo pg_createcluster 9.1 main --start

This will create the expected /etc/postgresql/9.1/main/ directory structure.

To migrate existing configurations to the new structure:

sudo pg_dropcluster --stop 9.1 main
sudo pg_createcluster 9.1 main --start
# Then copy your custom configurations from backup

Key files to be aware of in the new structure:

/etc/postgresql-common/postgresql.conf - Global defaults
/var/lib/postgresql/9.1/main/ - Data directory
/etc/postgresql/9.1/main/ - Cluster-specific configs (after cluster creation)

If your applications expect the old configuration path, you might need to update connection strings or configuration references. For example, in PHP:

// Old way
$host = '/var/run/postgresql/.s.PGSQL.5432';

// New recommended way
$host = 'localhost';
$port = '5432';

To verify everything is working correctly:

sudo -u postgres psql -c "SELECT version();"
sudo netstat -tulnp | grep postgres

If after these steps you still can't locate your configuration files or the service won't start, check:

sudo apt-get install --reinstall postgresql-9.1 postgresql-client-9.1 postgresql-common
sudo dpkg-reconfigure postgresql-common

If problems persist, consider filing a bug report with:

reportbug postgresql-9.1

---

When installing PostgreSQL 9.1 from backports on Debian Squeeze, you might notice the configuration files aren't where you'd normally expect them. Instead of /etc/postgresql/9.1/main, you only find /etc/postgresql-common. This is actually expected behavior in Debian's packaging.

# Expected traditional structure:
/etc/postgresql/
└── 9.1
    └── main
        ├── postgresql.conf
        ├── pg_hba.conf
        └── pg_ident.conf

# Actual structure in this case:
/etc/postgresql-common/
├── pg_upgradecluster.d
├── postgresql.conf
└── user_clusters

Debian's postgresql-common package introduced a new multi-version clustering system. The traditional directory structure was replaced with a more flexible approach:

• Configuration files are now managed through symlinks
• Multiple PostgreSQL versions can coexist more easily
• Cluster management is handled through pg_createcluster and pg_ctlcluster

Even without the traditional directory structure, your configuration files still exist. You can locate them with:

# List all clusters
pg_lsclusters

# Expected output:
Ver Cluster Port Status Owner    Data directory               Log file
9.1 main    5432 online postgres /var/lib/postgresql/9.1/main /var/log/postgresql/postgresql-9.1-main.log

The actual configuration files will be in the data directory under postgresql.conf:

# View the main configuration file
sudo nano /var/lib/postgresql/9.1/main/postgresql.conf

If you prefer the traditional layout, you can create it manually:

sudo mkdir -p /etc/postgresql/9.1/main
sudo cp /var/lib/postgresql/9.1/main/postgresql.conf /etc/postgresql/9.1/main/
sudo cp /var/lib/postgresql/9.1/main/pg_hba.conf /etc/postgresql/9.1/main/
sudo chown -R postgres:postgres /etc/postgresql

# Then edit the data_directory parameter in postgresql.conf
data_directory = '/var/lib/postgresql/9.1/main'

The newer approach actually provides more flexibility. Key commands to know:

# Create a new cluster
sudo pg_createcluster 9.1 mycluster --start

# Start/stop a cluster
sudo pg_ctlcluster 9.1 main start
sudo pg_ctlcluster 9.1 main stop

# Upgrade a cluster
sudo pg_upgradecluster 9.1 main

If services aren't starting properly, check:

# View PostgreSQL logs
tail -f /var/log/postgresql/postgresql-9.1-main.log

# Check service status
sudo service postgresql status

# Verify cluster is registered
sudo pg_lsclusters

Remember that in this packaging approach, the init script (/etc/init.d/postgresql) manages all clusters collectively rather than individually.