added postgresql

Postgresql.md

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+---
+Classes:
+  - IT Foundations
+---
+
+# Postgresql
+Postgresql is a popular open-source relational database, and is widely available on Linux.
+
+**Note:** A graphical interface for postgresql is something that will need to be installed separately, the only way to interact with the database that is installed by default is the `psql` command. To install the pgAdmin GUI program see [pgAdmin](#pgadmin) below.
+
+## Install
+All linux distributions package postgresql and you can just install the relevant package. Some common examples are below:
+
+### Arch
+```sh
+sudo pacman -S postgresql
+```
+
+### Debian/Mint/Ubuntu
+```sh
+sudo apt install postgresql
+```
+
+### Fedora
+```sh
+sudo dnf install postgresql-server
+```
+
+## Setup
+Initially the postgres database user will not have a password to allow access. To access the database run the following:
+```sh
+sudo -u postgres psql
+```
+
+From here you can do initial setup.
+
+For a simple setup where you just want to access from a client like pgAdmin, you can set a password for the `postgres` user with the following query:
+```sql
+ALTER USER postgres WITH PASSWORD 'new_password';
+```
+
+When done you can exit with the `\q` command.
+
+# pgAdmin
+pgAdmin is a graphical interface to configure and query postgresql.
+
+## Install
+Most linux distributions don't include pgAdmin from their default repositories, but we can either use pgAdmin's official repositories, or it is available as a flatpak:
+
+### Flatpak (universal)
+If you wish to install through flatpak ensure flatpak is setup, see [Flatpak](Flatpak.md) for details if not.
+
+If you have a graphical software manager/store it should be available there, to install via command-line:
+```sh
+flatpak install org.pgadmin.pgadmin4
+```
+
+### Arch (AUR Package)
+```sh
+yay -S pgadmin4-desktop-bin
+```
+
+### Debian/Ubuntu
+```sh
+# Install the public key for the repository (if not done previously):
+curl -fsS https://www.pgadmin.org/static/packages_pgadmin_org.pub | sudo gpg --dearmor -o /usr/share/keyrings/packages-pgadmin-org.gpg
+
+# Create the repository configuration file:
+sudo echo "deb [signed-by=/usr/share/keyrings/packages-pgadmin-org.gpg] https://ftp.postgresql.org/pub/pgadmin/pgadmin4/apt/$(lsb_release -cs) pgadmin4 main" > /etc/apt/sources.list.d/pgadmin4.list
+
+# Refresh package list
+apt update
+
+# Install pgAdmin
+sudo apt install pgadmin4-desktop libnss3 libgbm-dev libasound2-dev 
+```
+
+### Fedora
+```sh
+# Add the pgadmin repository
+sudo rpm -i https://ftp.postgresql.org/pub/pgadmin/pgadmin4/yum/pgadmin4-fedora-repo-2-1.noarch.rpm
+
+# Install pgAdmin
+sudo yum install pgadmin4-desktop
+```
+
+### Linux Mint
+```sh
+# Install the public key for the repository (if not done previously):
+curl -fsS https://www.pgadmin.org/static/packages_pgadmin_org.pub | sudo gpg --dearmor -o /usr/share/keyrings/packages-pgadmin-org.gpg
+
+# Create the repository configuration file:
+echo "deb [signed-by=/usr/share/keyrings/packages-pgadmin-org.gpg] https://ftp.postgresql.org/pub/pgadmin/pgadmin4/apt/noble pgadmin4 main" > /etc/apt/sources.list.d/pgadmin4.list
+
+# Refresh package list
+apt update
+
+# Install pgAdmin
+sudo apt install pgadmin4-desktop libnss3 libgbm-dev libasound2-dev
+```
+
+## Setup
+First you will need to register your running server:
+
+![Register Server](Screenshots/psql-register-server.png)
+
+In the General tab enter a name for your postgres server, then in the connection tab enter `localhost` for Hostname/address and enter the password for the postgres user:
+
+![Postgres Connection](Screenshots/psql-connection.png)
+
+Now click save and pgAdmin should be ready to use as normal!