Did I Already Install Postgres?

1. Check if the psql client exists

psql --version

If installed, you’ll see something like:

psql (PostgreSQL) 15.3

If not installed:

command not found

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2. Check if the postgres service exists

systemctl status postgresql

• If installed + running → you’ll see active (running)
• If installed but stopped → inactive
• If not installed → “Unit postgresql.service could not be found”

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3. Check installed packages (more definitive)

dpkg -l | grep postgres

This will list anything like:

postgresql
postgresql-15
postgresql-client-15

👉 This is the most reliable “is it installed at all” check.

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4. Check if the binary exists directly

which psql

• If installed → /usr/bin/psql
• If not → no output

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5. Bonus: check if a server is actually running

pg_isready

• If running → accepting connections
• If not → no response

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Quick mental model (very you-friendly)

• psql → “can I talk to postgres?”
• systemctl → “is postgres running as a service?”
• dpkg → “is postgres installed at all?”