If you install PostgreSQL on Debian, Ubuntu, or one of the other common Linux distributions, the login procedure is different from other operating systems. You can configure PostgreSQL to login using any method you wish. However, the default login method is to switch to the ‘postgres’ user (this login method does not use a password for the ‘postgres’ account), and then you’ll have access to PostgreSQL via the CLI.
After doing this, you can then create a less privileged user with a password to use in the applications you develop.
Default Login Password For PostgreSQL On Linux
There is no default password for PostgreSQL on Ubuntu nor Debian. You would use the following commands to log in and then load the PostgreSQL CLI respectively.
sudo -i -u postgres psql