Other Parts of This Series:

DevOps Linux Networking (Photo Credit: Unsplash)

DevOps Linux Networking (Photo Credit: Unsplash)

Story:

Rasel learned some of the basic and necessary things of linux. Now he wanted to finish his initial linux learning with one of the most important topics like linux networking and service manager. As devOps is heavily related to networking and service management and linux networking commands and systemctl command are essential for them. After that, he wanted to practice his learning with writing a little script.

Linux Networking:

As Linux is heavily used in server side, so managing and debugging the service to service connectivity is essential. And Linux networking related commands helps here to easily manage and operate those tasks.

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ip a

This command show all network interfaces and IPs.

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ifconfig

This is also do the same, but older command (may need to install).

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ping google.com (or) ping 192.168.1.1

This check if the system can reach Google domain name, also can use ip directly.

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telnet example.com 80

This check if port 80 is open, and it is older and insecure command for testing connectivity.

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ss -tuln

This show listening ports and services.

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netstat -tuln

This also do this but older alternative (install if needed).

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nslookup a.com

This shows IP and DNS info,

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dig a.com

This show more detailed DNS query (install dig if needed).

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ssh user@192.168.1.100

This is used to log in to remote server.

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ssh -i key.pem user@host

This use SSH key to connect or log in.

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ssh-keygen –t rsa

This is used to generate a key pair.

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ssh-copy-id user@remote\_host

This copies your local key to remote.

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scp file.txt user@host:/home/user/

This securely copy file to another remote server.

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scp user@host:/path/file.txt .

This securely download file from remote.

Example:

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ip a             # Show all network interfaces and IP addresses
ifconfig         # Older command, might need installation

ping google.com        # Check internet connectivity
ping 192.168.1.1       # Ping a specific device (e.g., your router)
telnet example.com 80               # Check if port 80 is open

nslookup example.com   # Simple DNS lookup
dig example.com        # Detailed DNS info (may need install)

ss -tuln               # Show listening ports and services
netstat -tuln          # Older alternative (install if needed)

ssh user@192.168.1.100              # Log in to remote server
ssh -i key.pem user@host            # Use SSH key to connect

ssh-copy-id user@remote_host        # Copies your local key to remote
ssh-keygen –t rsa                       # Generate a key pair

scp file.txt user@host:/path/       # Copy file to remote machine
scp user@host:/path/file.txt .      # Download file from remote

Compression and Archiving:

Sometimes we need to compress and archive files, folders to reduce its original size before move from local to remote server. It saves bandwidth and perform file transfer faster. Linux gives us many ways to do so.

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tar -czvf archive.tar.gz folder/

This compress folder.

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tar -xzvf archive.tar.gz

This do the opposite and extract contents.

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zip myfile.zip file.txt

This create zip.

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unzip myfile.zip

This extract zip.

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gzip file.txt

This compress.

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gunzip file.txt.gz

This decompress.

Example:

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tar -czvf archive.tar.gz folder/     # Compress folder
tar -xzvf archive.tar.gz             # Extract contents

zip myfile.zip file.txt              # Create zip
unzip myfile.zip                     # Extract zip

gzip file.txt                        # Compress (file.txt → file.txt.gz)
gunzip file.txt.gz                   # Decompress

System / Service Manager:

In server we deployed or install services. And its natural that we need to start, stop, enable auto start on startup and know their running status. Linux systemctl commands helps us to easily do that.

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sudo systemctl start nginx

This start a service.

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sudo systemctl stop nginx

This stop a running service.

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sudo systemctl restart nginx

This restart a stopped service.

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sudo systemctl status nginx

This gives the service status.

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sudo systemctl enable nginx

This enables a service auto start on boot.

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sudo systemctl disable nginx

This disables a service auto start on boot.

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systemctl list-units --type=service

This gives list of all service.

Example:

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sudo systemctl start nginx           # Start a service
sudo systemctl stop nginx            # Stop it
sudo systemctl restart nginx         # Restart it
sudo systemctl status nginx          # Show status

sudo systemctl enable nginx          # Auto-start on boot
sudo systemctl disable nginx         # Disable auto-start

systemctl list-units --type=service  # List all services

Little Scripting:

Scripting is the way of combining multiple commands in a single file (generally a bash file) and executes all the command at all. It helps to automate repetitive task and command to execute at once.

Like below we create a simple script that will create a file, add some text and print a hello message.

Step 1 (create a bash file):

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cat simple_script.sh

Step 2 (Add the commands):

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#!/bin/bash
cat text.txt
echo "Add text to file" >> text.txt
echo "Hello, DevOps!"

Step 3 (Make it executables):

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chmod +x simple\_script.sh

Step 4 (Run it):

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./simple_script.sh

Summary:

Linux networking tools like ip, ping and ss help you check connections, IPs, and open ports. Commands like ssh helps to remote login and telnet is useful for check connectivity. For moving files between systems, scp is useful. Compression tools like tar, zip, gzip let you package and reduce file sizes. systemctl is used to manage services like web servers (e.g., start, stop, enable on boot). Finally, with basic shell scripting using bash, you can combine multiple commands together to automate repetitive tasks.