Fixing PostgreSQL Connection Error: No such file or directory

When working with PostgreSQL on macOS, you may encounter the error:

psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such file or directory

This typically indicates that your PostgreSQL server isn't running or can't be accessed through the expected Unix socket. Let's explore the common causes and effective solutions.

Common Causes

• Improper shutdown: Force-quitting applications or unexpected system shutdowns
• Stale PID file: A leftover postmaster.pid file from a previous session
• Multiple PostgreSQL versions: Conflicts between different installations
• Incorrect configuration: Wrong port settings or data directory paths
• Disk space issues: Full storage preventing server startup

Step-by-Step Solutions

1. Check if PostgreSQL is Running

First, verify if PostgreSQL is actually running:

pgrep -l postgres

If no processes are listed, your server isn't running.

2. Remove Stale PID File (Most Common Fix)

The most common solution is to remove the stale postmaster.pid file and restart PostgreSQL:

Intel Mac

rm /usr/local/var/postgres/postmaster.pid
brew services restart postgresql

Apple Silicon/M1/M2/M3

rm /opt/homebrew/var/postgres/postmaster.pid
brew services restart postgresql

Specific PostgreSQL Version

rm /opt/homebrew/var/postgresql@15/postmaster.pid
brew services restart postgresql@15

WARNING

Always stop the PostgreSQL service before removing the PID file:

brew services stop postgresql
# or for specific version
brew services stop postgresql@15

3. Check PostgreSQL Logs

If the above doesn't work, examine the logs for specific error messages:

tail /usr/local/var/log/postgres.log
# or
tail /opt/homebrew/var/log/postgresql@15.log

Look for messages like "FATAL: lock file 'postmaster.pid' already exists" or other startup errors.

4. Verify Disk Space

A full disk can prevent PostgreSQL from starting:

df -H

Clear space if your root drive is near capacity.

5. Check PostgreSQL Configuration

Ensure PostgreSQL is configured to use the standard port (5432):

# Check which port PostgreSQL is using
cd /opt/homebrew/var/postgres
grep "port =" postgresql.conf

If it's using a different port, you can either:

• Change the configuration to use port 5432
• Connect using the specific port: psql -p 5433

6. Recreate Default Database

Sometimes the default database needs to be recreated:

createdb
psql -h localhost

7. Complete Reinstall (Last Resort)

If all else fails, you may need to completely reinstall PostgreSQL:

brew uninstall --force postgresql
brew install postgresql
brew services start postgresql

Prevention Tips

1. Always stop PostgreSQL properly:

   brew services stop postgresql

2. Avoid force-quitting applications that might be connected to PostgreSQL

3. Keep regular backups of important databases

4. Monitor disk space to prevent storage-related issues

Alternative: Use Docker

Consider using PostgreSQL via Docker to avoid local installation issues:

docker run --name postgres -e POSTGRES_PASSWORD=mysecretpassword -d -p 5432:5432 postgres

When to Seek Further Help

If none of these solutions work, you might have:

• File permission issues in PostgreSQL data directory
• Corrupted database files
• Conflicts with other database installations

Check PostgreSQL's official documentation or seek help in community forums with details about your specific setup and error messages from the logs.

INFO

Remember that the exact file paths may vary depending on your PostgreSQL version and installation method. Use brew info postgresql to find the correct paths for your setup.