Monday, November 29, 2021

Who Has Rebooted The Linux System?

There are many times that we get puzzled with this question "Who has rebooted the system?". Was this triggered by a user or done by some kernel threads? What was the reason why the server was rebooted? Of course, a running system should not be rebooted without a reason, as this incurs downtime and service disruptions. There are many ways to avoid service disruption by setting up High Availability (HA) so that one server down/reboot would not cause any downtime as the application/service would continue to work from another server in this setup. However, in Load Balancer (LB) mode where there are multiple nodes serving the applications and node down would certainly be balanced by other nodes in the LB setup. Let's come back to our main agenda which is to track the system reboot activity. Yes, in this blog post we would talk about this topic and different ways to detect/identify this from a Linux system. 

Monday, June 14, 2021

What or Why DNF?


DNF or Dandified YUM is the next generation version of yum. 


DNF is a software package manager that installs, updates, and removes packages on RPM-based Linux distributions. It automatically computes dependencies and determines the actions required to install packages. DNF also makes it easier to maintain groups of machines, eliminating the need to manually update each one using rpm. Introduced in Fedora 18, it has been the default package manager since Fedora 22. So, in this post I’m not going to discuss the usage of DNF rather on why and advantages of using it. By default, DNF comes pre-installed on RHEL8.x releases. The "yum" command is a symbolic link to the "dnf" binary now.


Wednesday, May 12, 2021

Different Fault Tolerance Options At System/Patch Level In Linux

 


As we all know, patching is an essential & integral part of any IT infrastructure. It could be cloud based systems (virtual) or an on-premise virtual systems or physical servers running in a dedicated data center. Patch management has now become an important buzzword in corporate IT organizations and business offices. Patch management is basically the process of acquiring, testing and installing multiple code changes (patches) to systems software and applications. 

Monday, December 7, 2020

The Power Of A Dot In Linux Environment


Yes, there are several places where a dot (.) is being used in Linux terminal/Shell. In addition, a dot would depict some meaning when shown in the output of a command. Let us see the different places where we would normally use a dot and explore the other places where one could get to see this in Linux. The usage of a dot that is documented here is excluding the standard or regular use that is not specific to Linux/Unix and it is common across computer environments. Such as in representing a FQDN (Fully Qualified Domain Name) separated with dot, IP Address where each bit (from 0 to 255) is separated by a dot etc, 

Monday, October 12, 2020

Some Differences Between Red Hat Satellite & SUSE Manager


Red Hat SatelliteSUSE Manager
Upstream VersionIn Red Hat Satellite (version 6 on-wards) there are multiple open-source upstream projects involved such as Foreman, Katello, Pulp, Candlepin etc,. In earlier version which is Satellite version 5, spacewalk was being used.Uyuni (a fork of Spacewalk, based on SaltStack) is the upstream for SUSE Manager 4 and later releases. "Spacewalk" was used earlier.
Current Version*Red Hat Satellite 6.7SUSE Manager 4.1

Friday, July 3, 2020

Top 10 Dangerous Operations or Commands To Be Executed Carefully In Linux


I’ve come up with these 10 categories of tasks/commands/operations which would render a system un-usable or may cause service disruption or network outage when executed without proper precaution or understanding of the impact of the command and how it works. Most of these commands would also have a forceful execution option which doesn’t even raise a prompt before execution(when run by root or any privileged sudo user). This is in addition to the notorious recursive & forceful file removal command (rm -rf /). I’ve not considered the standard shutdown/reboot commands since these are known and understood by the command itself. Some of the commands would certainly require a root privilege, but the point here is that even as a root user, such commands should never be executed without understanding the details.