Author: Sahil Suri

Understanding SysVinit system manager

Introduction On Centos/RHEL 6 systems, the grub boot loader will load the kernel and initial RAM disk. Once the kernel has finished its startup procedure, it will hand over control to a startup manager. The SysVinit program is one such startup manager which had been used in Red Hat based systems up until RHEL 6. As of RHEL 7 onwards, the SysVinit system has been replaced in favor of systemd. In this article, we will explain the functioning of init along with run levels which describe the system state. The name SysVinit has derived from system 5 Unix and has been widely adopted in Linux as the replacement for the original BSD init.   What is init? The kernel starts the init process /sbin/init with the process id 1. The init process is responsible for coordinating the start of the rest of the system services, configuring the user environment and essentially bringing the system to a functional state. Let’s take a look at the init process using the Linux top command: [sahil@linuxnix:~] $ top -p 1 -n 1 top - 14:51:28 up 210 days, 20:55, 1 user, load average: 0.00, 0.00, 0.00 Tasks: 1 total, 0 running, 1 sleeping, 0 stopped, 0 zombie Cpu(s): 1.0%us, 0.3%sy, 0.0%ni, 98.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1921184k total, 1597396k used, 323788k free, 365232k buffers Swap: 3768316k total, 88800k used, 3679516k free, 770044k...

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What are Meltdown and Spectre vulnerabilities and how patch them in RHEL/Centos

Introduction Recently researchers at Google’s Project Zero have discovered two major vulnerabilities impacting almost all the processors made in the last 20 years. These vulnerabilities have been named Meltdown and Spectre. In this article, we will describe what these vulnerabilities are, how to check if your system is affected and how to patch an affected Linux system. We will also briefly discuss the potential negative impact of applying the patch. Let’s now understand what these vulnerabilities are all about.   Meltdown Meltdown affects Intel processors and works by breaking through the barrier that prevents applications from accessing arbitrary locations in kernel memory. In simpler words, the Meltdown vulnerability allows a program to access the kernel’s private memory areas.  These memory locations contain data in unencrypted format giving the attacker access to potentially sensitive information.   Spectre The Spectre vulnerability affects Intel, AMD, and ARM processors and enables an attacker to access sensitive information misleading applications into accidentally disclosing information that would normally be inaccessible, safe inside their protected memory area. This means that a malicious program can trick other programs like your web browsers to reveal password information. The creator of Linux, Linus Torvalds has publically criticized Intel’s approach towards handling the discovery of these bugs and has raised questions as to how they treat customers even when critical bugs are discovered. Operating system vendor RedHat has assigned CVE...

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Ansible – presenting a season’s greetings playbook

Introduction As this year draws to an end i.e. today is the 31st of December as I’m writing this article. We are sure that your email and phone inboxes would be filled with wishes from your loved ones and friends. We wanted to take this opportunity to share our best wishes to you in an interesting Ansible way. In this article, we will share an Ansible playbook which prints the line “HAPPY NEW YEAR TO ALL” in a very colorful manner. We’ll show you how to execute the playbook properly but we will not do a deep dive into the plugins that are responsible for generating the output. To get started we need the GitHub repository ansible-cowmas. You can download the repository to your local system from the URL or you can clone it directly if you are using git on your local system. I’ve downloaded the repository from the URL and copied it to my local system. [root@linuxnix seasons_greetings]# ls ansible-cowmas-master.zip Let’s extract this zip file now. [root@linuxnix seasons_greetings]# unzip ansible-cowmas-master.zip Archive: ansible-cowmas-master.zip 25dda48a4be957b306dd785ee512835ee9df5711 creating: ansible-cowmas-master/ inflating: ansible-cowmas-master/.gitignore inflating: ansible-cowmas-master/LICENSE inflating: ansible-cowmas-master/README.md inflating: ansible-cowmas-master/ansible.cfg creating: ansible-cowmas-master/callback_plugins/ inflating: ansible-cowmas-master/callback_plugins/cowmas.py inflating: ansible-cowmas-master/hello_world.yml [root@linuxnix seasons_greetings]# ls ansible-cowmas-master ansible-cowmas-master.zip [root@linuxnix seasons_greetings]# Now let’s take a peek at the contents of the directory. [root@linuxnix seasons_greetings]# cd ansible-cowmas-master/ [root@linuxnix ansible-cowmas-master]# ls ansible.cfg callback_plugins hello_world.yml LICENSE README.md [root@linuxnix ansible-cowmas-master]#   The callback_plugins directory contains a python script which...

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ABOUT ME..!

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My name is Surendra Kumar Anne. I hail from Vijayawada which is cultural capital of south Indian state of Andhra Pradesh. I am a Linux evangelist who believes in Hard work, A down to earth person, Likes to share knowledge with others, Loves dogs, Likes photography. At present I work at Bank of America as Sr. Analyst Systems and Administration. You can contact me at surendra (@) linuxnix dot com.