Postgres.app can’t start when another server is already running on the same port (default: 5432). We recommend to uninstall other PostgreSQL installations before using Postgres.app.
Before you uninstall, make sure to back up any data you might have stored in the database using pg_dump. See Migrating data for details.
After uninstalling, open “Activity Monitor” and make sure there are no processes named “postgres” or “postmaster”; otherwise Postgres.app might not be able to start.
$ brew remove postgresql
First use the installed command to determine which version of the PostgreSQL server you have installed:
$ sudo port installed
Then uninstall the server. If you are using version 9.4, the command would be:
$ sudo port uninstall postgresql94-server
After uninstalling, the server might still be running. Use Activity Monitor to kill the server processes, or reboot your Mac.
EnterpriseDB provides an uninstaller that can automatically uninstall PostgreSQL. You can find it in the installation directory.
The default EnterpriseDB installation directory is /Library/PostgreSQL. To open this directory, use the “Go To Folder” command in Finder (⌘⇧G) and type /Library/PostgreSQL.
Then double click on the “uninstall-postgresql” application.
To uninstall the Kyng Chaos distribution, follow these instructions.