postgres in debian

// switch to root 

// create the file as below
nano /etc/apt/sources.list.d/pgdg.list

// save the link in above file: 
deb http://apt.postgresql.org/pub/repos/apt/ your_debian_version-pgdg main

// import the repository signing key
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add -

// update the package list
apt-get update 

// install postgres
apt install postgresql-version_you_want_to_install

// start postgressql
systemctl start postgresql

// change password
sudo -u postgres psql postgres

postgres=# \password postgres
Enter new password: set_your_new_password_here
Enter it again: enter_your_new_password_again