Explore information related to networking


Linux IP Command with Examples - An overview ?

This article covers the practical use cases of the Linux IP command. IP stands for Internet Protocol. IP command is used to show or manipulate routing, devices, and tunnels. It is similar to ifconfig command but it is much more powerful with more functions and facilities attached to it. It can perform several other tasks like configuring and modifying the default and static routing, setting up tunnel over IP, listing IP addresses and property information, modifying the status of the interface, assigning, deleting and setting up IP addresses and routes.


Linux system commands:

  • arp — Manipulate the system ARP cache.
  • ifconfig — View or modify the configuration of network interfaces.
  • netstat — Print information about network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.
  • route — Display and manipulate the IP routing table.
  • tcpdump — Capture raw network traffic.

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Prevent SSH From Timing Out - Best Method ?

This article covers different ways of keeping SSH sessions alive and preventing them from needlessly timing out. These are handy tips that you can use especially when there are no associated risks with someone taking over your SSH session when you are away. SSH sessions will timeout and the client will automatically be disconnected from the server after being idle or inactive for a while. 


To Avoid SSH timeout from the server:

1. Edit SSHd configuration file using your favorite editor,

$ sudo vi /etc/ssh/sshd_config

2. Set these options as the followings:

TCPKeepAlive no 
ClientAliveInterval 30
ClientAliveCountMax 240

Here, the server will not send the TCP alive packet to check if the client's connection is working, yet will still send the encrypted alive message every 30 seconds. It will only disconnect after at least 2 hours of inactivity. 

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Change the SSH Port on Ubuntu 20.04 Linux Server

This article covers how to change SSH port on your Linux system. SSH (Secure shell) is a cryptographic network protocol used to connect to a remote server securely and it transfer the data in encrypted form between the host and the client.

The default TCP port for SSH is 22, and by changing this default port to the other, it can prevent automated bots and malicious users from being brutally forced into the server.

Before changing the default SSH port number, can check the current port with the below command:

# netstat -ntlp | grep ssh


To change the SSH port:

1. Open the main SSH daemon configuration file /etc/ssh/sshd_config:

# vi /etc/ssh/sshd_config

2. Now search line begins with Port 22 and add hashtag (#) in front of that line. 

3. Then add a new Port line below with the custom port.

Note: Replace the sample port number with the custom port number that needs to be set.

4. Save and exit.


How to Restart the SSH daemon for the changes to take effect ?

Run the below commands to restart the SSH daemon and verify that the port changed:

# systemctl restart sshd
# netstat -ntlp | grep ssh

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Configure Static IP Addresses on Ubuntu 18.04 Server - Step by Step Process ?

This article covers method to set up a static IP address on Ubuntu 20.04. Basically, in most network configurations, the IP address is assigned dynamically by the router DHCP server. 

The recommended way to assign a static IP address to a device on your LAN is to configure a Static DHCP on your router. Static DHCP or DHCP reservation is a feature found on most routers which makes the DHCP server to automatically assign the same IP address to a specific network device, each time the device requests an address from the DHCP server. This works by assigning a static IP to the device's unique MAC address.


To Get the name of network interface and the default gateway in Linux:

You can either use ip command or the network manager CLI like this:

$ nmcli d

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Step by step process to install and configure HAproxy on Ubuntu 20.04 LTS ?

This article will guide you on how to #install and configure #HAproxy load balancer on the #Linux system. 

You will learn the basic setup and configuration of HAproxy as a load balancer for #Apache web servers. Also, we looked at some commands for managing the HAproxy server. In the end, we tested the load balancing through the browser and the #curl command. 

HAProxy is free, open source #software that provides a high availability #load #balancer and proxy server for #TCP and HTTP-based applications that spreads requests across multiple servers.

To Deploy on Linux :

1. Download the source code of HAProxy.

2. Unzip the file into the desired location tar xvzf haproxy-1.8-dev1.

3. Compile the source code.

4. Create config file haproxy.cfg with the configuration details.

5. Start the haproxy with ./haproxy -f haproxy.

6. Access the status page on http:localhost:9999/stats.

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Steps to restart network services in Linux ?

This article will guide you on how to start, stop, and restart the #network service on different Linux distribution like Ubuntu, #Debian, Linux Mint, and CentOS 8. Moreover, you can troubleshoot the network #error through the #NetworkManager tool on #CentOS 8.

Please don't stop services if you have a remote ssh connection that may create a problem.

Restarting networking on a desktop machine will cause dbus and a bunch of #service to stop and never be started again, usually leading to the whole system being unusable.

To restart a Linux service:

1. Linux provides fine-grained control over system services through #systemd, using the systemctl command.

2. To verify whether a service is active or not, run this command: sudo systemctl status apache2.

3. To stop and restart the service in Linux, use the command: sudo systemctl restart SERVICE_NAME.

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