How to Completely Remove and Reinstall PostgreSQL on Ubuntu

Postgresql: This refers to the open-source relational database management system you want to remove and reinstall.

Ubuntu: This is the Linux operating system where PostgreSQL is installed. Ubuntu uses a package manager to handle software installations and removals.

Uninstallation: This refers to the process of removing PostgreSQL completely from your system.

Here's how the purging and reinstalling process works:

1. Uninstalling PostgreSQL:

   • The apt-get command is used to interact with the Ubuntu package manager.
   • The purge flag with remove tells apt-get to uninstall the software and also remove any leftover configuration files.
   • postgresql and postgresql-* (wildcard) target the main PostgreSQL package and any additional packages associated with it.

2. Cleaning Up (Optional):

   • While purge removes most files, there might be lingering data directories.
   • The commands dpkg -l | grep postgres or find / -name postgresql can help locate leftover traces (use with caution).

Additional Notes:

• This process completely removes any existing databases or configurations. Back up your data if needed before purging.
• If you just want to reset a single PostgreSQL server (cluster), there are tools like pg_dropcluster available, which might be preferable to a full purge and reinstall.

sudo apt-get --purge remove postgresql\*

This command uses sudo to run with administrator privileges, apt-get to interact with the package manager, --purge flag to remove configuration files, and remove to uninstall the packages. Finally, postgresql\* targets the main PostgreSQL package and any additional packages starting with "postgresql".

Option 1: Using dpkg

dpkg -l | grep postgres

This command uses dpkg for low-level package management and grep to filter the output. It will list any installed packages with "postgres" in the name, helping you identify leftover traces.

Option 2: Using find (use with caution)

sudo find / -name postgresql

This command searches the entire system for directories or files named "postgresql". Use caution as this can return a large amount of data and might include unrelated files. It's recommended for experienced users only.

sudo apt-get install postgresql

By default, apt-get installs the latest PostgreSQL version available in your Ubuntu repositories. If you want a specific version, you can specify it during installation. Here's an example for installing version 14:

sudo apt-get install postgresql-14

Using Repositories for Latest Versions:

The official Ubuntu repositories might not have the most recent PostgreSQL version. You can add external repositories maintained by the PostgreSQL project itself. This method requires extra configuration and might have compatibility risks with your Ubuntu version. Refer to the official PostgreSQL documentation for detailed instructions on adding repositories:

Dropping unwanted PostgreSQL servers (clusters):

If your goal is to reset a single PostgreSQL server (cluster) and not the entire installation, you can use the pg_dropcluster tool. This approach is less disruptive than a full purge and reinstall. Here's an example:

sudo su - postgres -c psql -h localhost -p <port_number> -U postgres -c "DROP CLUSTER <cluster_name>;"

Important notes for pg_dropcluster:

• Replace <port_number> with the port your PostgreSQL server is running on (default 5432).
• Replace <cluster_name> with the actual name of the cluster you want to drop.
• This command requires running the command as the postgres user.

Using a Different Database Management System:

If your needs have changed, consider using a different database management system altogether. Here are some popular alternatives to PostgreSQL:

• MySQL: Another open-source relational database system with a large user base.
• MariaDB: A community-developed fork of MySQL, known for its compatibility and stability.
• SQLite: A lightweight, embedded database suitable for smaller projects or local data storage.