Centos Interview Questions and Answers

CentOS is one of the Linux distribution that is affiliated with the Red Hat. It is an open-source operating system that was first launched in 2004. This free operating system officially supports x86-64 architecture which mainly targets the servers, desktop computers, and workstations. It is a community-driven free software that is consistent and easy to use.

The CentOS variant is a special edition of CentOS. With this variant, you can allow another open-source project to run more effectively using CentOS as the base platform. The CentOS variant starts with the core distribution and replaces the specific subsets of packages.

The current stable release of the CentOS is version 8.1.1911 that was released in January 2020.

The nmcli is a command-line tool in CentOS for controlling the Network manager. This tool is used to display network device status, create, edit, activate, deactivate, and delete network connections.

The Yellow Dog Updater (YUM) is the default package manager in CentOS. It is used to install and update packages in the CentOS.

The other package manager in CentOS is RPM, DNF, pip, dpkg, and aptitude.

You can use the network manager service to restart a service in the CentOS. The command used to restart a service in the CentOS is "$sudo systemctl restart NetworkManager.service". You can also use the nmcli tools to restart network service. Use the following commands in the nmcli tool to restart a network service,

$sudo nmcli networking off
$sudo nmcli networking on

To create a Sudo user on the CentOS, follow these steps on your command-line shell.

1. Log in to your server $ssh root@server_ip_address
2. Create a new user account $useradd username
3. Set the user password $passwd username
4. Add the new user to the sudo group $usermod -aG wheel username
5. To switch to the newly created user $su - username

Some of the basic CentOS commands are,

• Sudo - runs a command as superuser
• Yum - lets you install and update packages
• Ls - lists the contents of the directory
• Cd - used to change directory
• Pwd - displays the pathname
• Mv - used to move files
• Cp - used to copy files
• Mkdir - used to create a directory
• Who - used to check who is logged on
• Clear - used to clear the terminal window
• Nano - opens a text editor

You can remove a user in centos by using the userdel command

//syntax
# userdel -r user
The above command removes the user names “user”.

We can use the following command to enable or disable service on centos

To enable a service, use the following command,

Systemctl enable <service_name>

To disable a service, use the following command,

Systemctl disable <service_name>