CentOS related tutorial/FAQ

Check how many CPUs are there in Linux system

last updated October 15, 2018 in CentOS, Debian / Ubuntu, Hardware, Linux, RedHat and Friends, Suse

I am a new Linux user. How do you check how many CPUs are there in Linux system using the command line option?

CentOS 7 Run Script When Network Interface is Up (Network Manager)

last updated October 15, 2018 in CentOS, Linux, Networking, RedHat and Friends

I want to run a shell script or other program immediately after my network interface goes up on a CentOS 7 / RHEL 7 server. I created /sbin/ifup-local, but it is not working on a CentOS 7 box but works perfectly on CentOS 6. I am using NetworkManager with CentOS 7. How do I run ifup-post or ifup-pre scripts?

Ansible reboot Linux machine or server with playbooks

last updated October 6, 2018 in CentOS, Debian / Ubuntu, FreeBSD, Linux, OpenBSD, RedHat and Friends, Suse, UNIX

I need to reboot the VM or bare metal Linux machine/server using Ansible and wait for it to come back, but it does not work with playbook as descried here. How to reboot Linux server with Ansible? How do I reboot and wait for reboot to complete in Ansible playbook for multiple Linux servers?

CentOS 7.0 Set Up OpenVPN Server In 5 Minutes

last updated September 29, 2018 in CentOS, Linux, OpenVPN

I am a new CentOS Linux 7.0 server user. How do I set up an OpenVPN Server on CentOS Linux version 7.0 server to shield my browsing activity from bad guys on public Wi-Fi, and more?

CentOS 7 dig command not found – How to install dig on CentOS

last updated September 29, 2018 in CentOS, Linux, Package Management

I deployed CentOS 7 Linux minimal deployed in the cloud. However, I am unable to find the dig command on my newly created CentOS 7 server. It says ‘-bash: dig: command not found‘ I tried yum install dig, but it failed. How do I install dig command on CentOS 7 Linux using the command line?

Linux find largest file in directory recursively using find/du

last updated September 19, 2018 in CentOS, Debian / Ubuntu, Linux, RedHat and Friends, Suse

I have 500GB SSD installed on my Linux server. My web server is running out of the disk space. I need to find a biggest or largest file concerning file size on the disk. How do I find largest file in a directory recursively using the find command?

Linux copy and clone USB stick including partitions command

last updated August 11, 2018 in CentOS, Debian / Ubuntu, Linux, RedHat and Friends, Suse

I need to copy and clone existing data from a USB stick. How do I clone a bootable USB key/pen drive on Linux? How do I clone a USB stick including partitions on Linux operating system?

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