FATAL ERROR lock file “postmaster.pid” already exists

Question

I have recently installed PostGIS on my Mac (El Capitan 10.11.4, Postgres is version 9.5.1) using Homebrew, and I am following these instructions - http://morphocode.com/how-to-

Answer 1

Since you can connect to the database, you don't need to start the server again - it's already running.

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pg_ctl is used to control the PostgreSQL server. Since your server is already started, your command:

pg_ctl -D /usr/local/var/postgres start

Returns an error, saying that there is a lock on postmaster.pid - which is true since there is already a server running under that PID.

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There are two ways:

1. The most basic way - skip that step, your server is already running!
2. Executing a needless operation - stopping the server, and then starting it again.

You could stop your server doing :

pg_ctl -D /usr/local/var/postgres stop

So that you won't have the lock on postmaster anymore and you could use your command to start it again.