DevOps Configuration Guides and Snippets

Set up GitHub SSH connection on VPS

Terminal commands:

Generate SSH key pair: ssh-keygen -t rsa -b 2048
Navigate to SSH directory: cd ~/.ssh/
View public key: cat id_rsa.pub
Copy the entire public key content (starts with ssh-rsa)
Go to GitHub Settings → SSH and GPG Keys
Click "New SSH Key"
Paste key and save
Test connection: ssh -T git@github.com

Important Notes

Run eval "$(ssh-agent -s)" in each new session
Use SSH URLs for Git operations

Enable Firewall Using UFW

Terminal Command:

sudo ufw enable
Press y and hit Enter

Allow Applications Through UFW

List available applications: sudo ufw app list (to view available apps)
Allow an application (e.g., OpenSSH): sudo ufw allow OpenSSH (replace "OpenSSH" with your desired app)

Resolve Python Access Issue on VPS

Error Message

Terminal Command:

sudo chmod +x /usr/bin/python3

Run pgAdmin in Docker

docker run -p 5050:80 -e "PGADMIN_DEFAULT_EMAIL=admin@admin.com" -e "PGADMIN_DEFAULT_PASSWORD=admin" -d dpage/pgadmin4
Navigate to http://159.65.145.88:5050 to access pgAdmin.
Enter the email and password specified in Point 1.

Connect Local PostgreSQL to pgAdmin4 in Docker

Retrieve Docker Container IP:

docker ps
docker inspect <container_id> (replace <container_id> with your actual container ID)
Scroll down to the Network section.
Add the following line to your pg_hba.conf file:
host all all 172.17.0.2/32 md5 (ensure you add "/32" for IPv4 or "/128" for IPv6)
Click on Add Server, enter your server IP address, select a database, and provide the database password. (Using a super user account is recommended)

Free Up a Port in aaPanel

Navigate to Security > Firewall, add the desired port, and click the Open button.

Add a New User to VPS

Terminal Commands:

adduser user_name (Replace user_name with the desired username. You will be prompted to enter a password and additional information.)
adduser user_name sudo (Grant sudo privileges to the new user)

Access PostgreSQL in Terminal

Terminal Commands:

su - postgres
psql

Essential PostgreSQL Commands

\l (List all databases)
\q (Quit PostgreSQL)

Set Up Go (Golang)

Create a project directory and navigate into it:
Open the terminal in that directory.

Terminal Commands:

wget https://go.dev/dl/go1.19.4.linux-amd64.tar.gz
tar -xvf golang_download_file_name.tar.gz (Replace golang_download_file_name.tar.gz with the actual file name)
sudo mv go /usr/local (Move Go to the local directory)

Miscellaneous Tips

UFW (Uncomplicated Firewall)
Linux systems automatically create a tmp folder after booting.
Location of the tmp folder: root directory. (If not found, type cd and press Enter to navigate to the tmp folder)
Navigate inside the tmp folder.

PostgreSQL Installation and Setup

sudo apt update && sudo apt -y full-upgrade
sudo reboot
sudo apt update
sudo apt install curl gpg gnupg2 software-properties-common apt-transport-https lsb-release ca-certificates
curl -fsSL https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/postgresql.gpg
echo "deb http://apt.postgresql.org/pub/repos/apt/ $(lsb_release -cs)-pgdg main" | sudo tee /etc/apt/sources.list.d/pgdg.list
sudo apt update
sudo apt install postgresql-13 postgresql-client-13

Configure PostgreSQL for Remote Connections

Edit PostgreSQL configuration: sudo nano /etc/postgresql/13/main/postgresql.conf (replace "13" with your PostgreSQL version)

In postgresql.conf, set listen_addresses to your VPS IP address. For example:

                                listen_addresses = '192.168.10.11'

Save and close the file.
Edit pg_hba.conf: sudo nano /etc/postgresql/13/main/pg_hba.conf

Change the host entry from:

                                # Accept from anywhere
                                host all all 0.0.0.0/0 md5

To:

                                # Accept from trusted subnet
                                host all all 10.10.10.0/24 md5

Save and close pg_hba.conf.
sudo systemctl restart postgresql

GitHub CI/CD Packages for VPS Deployment

SSH Action for GitHub
SSH Key Action for GitHub

Reference Video Watch Here

CI/CD Boilerplate

Variables formatted as ${{ variable_name }} can be stored in the repository's Settings under Secrets and Variables in the Actions section.

Create Variables

In the Actions section of Secrets and Variables, click on New Repository Secret, then enter a Name and Secret.
Example: Name: HOST Secret: localhost
Access your secret key using ${{ secrets.HOST }}

Check Running Service Status

systemctl status <service_name> (e.g., nginx, mysql)
systemctl restart <service_name>
systemctl stop <service_name>

Angular Configuration for Nginx

                        location / {
                            # First attempt to serve request as file, then
                            # as directory, then redirect to index(angular) if no file found.
                            try_files $uri $uri/ /index.html;
                        }

Resolve "node: Permission Denied" Error

sudo chmod 777 -R Your_Dir/ (Replace Your_Dir with your directory)

Deploy a Static Website

sudo apt install nginx
sudo ufw app list (to check if Nginx HTTP and Nginx HTTPS exist)
sudo ufw enable
sudo ufw allow 'Nginx HTTP'
sudo ufw allow 'Nginx HTTPS'
systemctl status nginx (to check Nginx status)
sudo mkdir -p /var/www/html/your_folder
sudo chown -R $USER:$USER /var/www/your_folder
sudo chmod -R 755 /var/www/your_folder
sudo nano /etc/nginx/sites-available/your_domain

Configure Nginx by replacing your_folder with your directory and your_domain with your domain name. Ignore sections managed by Certbot.

                            server {
                                root /var/www/your_folder;
                                index index.html index.htm index.nginx-debian.html;
                                
                                server_name your_domain;
                                
                                location / {
                                    try_files $uri $uri/ /index.html;
                                }
                                
                                listen [::]:443 ssl ipv6only=on; # managed by Certbot
                                listen 443 ssl; # managed by Certbot
                                ssl_certificate /etc/letsencrypt/live/path/fullchain.pem; # managed by Certbot
                                ssl_certificate_key /etc/letsencrypt/live/path/privkey.pem; # managed by Certbot
                                include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
                                ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
                            }
                            server {
                                if ($host = your_domain) {
                                    return 301 https://$host$request_uri;
                                } # managed by Certbot
                                
                                listen 80;
                                listen [::]:80;
                                
                                server_name your_domain;
                                return 404; # managed by Certbot
                            }

sudo ln -s /etc/nginx/sites-available/your_domain /etc/nginx/sites-enabled/
sudo nginx -t

Deploy a Node.js Application

Run your Node.js backend.
Update Nginx configuration as shown below, replacing http://localhost:3000/ with your application's URL.

                            server {
                                server_name nodejs.your_domain.com;
                                
                                location / {
                                    proxy_set_header X-Real-IP $remote_addr;
                                    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                                    proxy_set_header Host $host;
                                    proxy_set_header X-NginX-Proxy true;
                                    proxy_pass http://localhost:3000/;
                                    proxy_redirect http://localhost:3000/ https://$server_name/;
                                }
                                
                                listen 443 ssl; # managed by Certbot
                                ssl_certificate /etc/letsencrypt/live/path/fullchain.pem; # managed by Certbot
                                ssl_certificate_key /etc/letsencrypt/live/path/privkey.pem; # managed by Certbot
                                include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
                                ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
                            }
                            server {
                                if ($host = your_domain) {
                                    return 301 https://$host$request_uri;
                                } # managed by Certbot
                                
                                listen 80;
                                server_name your_domain;
                                return 404; # managed by Certbot
                            }

Ensure your Node.js app is running on port 3000 or update the proxy settings accordingly.

Add Free SSH with Certbot

sudo apt install snapd
sudo snap install --classic certbot
Run certbot in your terminal:
You will see a list of hosted websites. Select the desired site and generate an R3 SSL certificate.