Linux

Yum ExcludeWhen you perform yum update, it will download the latest version of all the packages that are installed on your system, and upgrade them to the latest version.

You may be in situation where you might not want yum to automatically update one (or more) specific package.

In those situations, use the yum exclude option as shown in the examples below.
(more…)

10 pidstat Examples to Debug Performance Issues of Linux Process

by Balakrishnan Mariyappan on November 12, 2014

pidstat stands for PID Statistics.

This tool can monitor an individual process that is managed by kernel and generate a report. It can monitor either a specific PID (process id), or all the process running on the system.

pidstat is a part of sysstat utility.

This tool reports various statistics including CPU used by a process, disk usage statistics of a process, statistics for threads associated with selected tasks and child processes.
(more…)

How to Install Linux KVM and Create Guest VM with Examples

by Karthikeyan Sadhasivam on October 20, 2014

Linux KVMKVM stands for Kernel-based Virtual Machine.

As the name suggests, this is kernel based virtualization technology for Linux OS on hardware that supports virtualization.

The guest operating systems can be fully virtualized or para virtualized.
(more…)

How to Fix Bash Shellshock CVE-2014-6271, CVE-2014-7169 on Linux

by Ramesh Natarajan on September 29, 2014

bash promptCVE-2014-6271 is a high impact critical fix. If you are running a Linux system, you should fix this vulnerability.

This CVE-2014-6271 (and CVE-2014-7169) vulnerability is also called as Shellshock.

A flaw was found in the way Bash evaluated certain specially crafted environment variables. An attacker could use this flaw to override or bypass environment restrictions to execute shell commands. Certain services and applications allow remote unauthenticated attackers to provide environment variables, allowing them to exploit this issue.
(more…)

How to Speedup Linux Boot Process using Startpar Command Examples

by Karthikeyan Sadhasivam on September 10, 2014

In a typical scenario, during the boot process, the run-level system startup scripts are executed one-by-one.

A particular run level startup script will not execute until the previous script is executed completely. If a particular service during the startup is hanging for some reason, it might take a while before it times-out and move on to the next startup script.

Startpar utility is used to run multiple run-level scripts in parallel. This helps to speed up the boot process of your server.
(more…)

How to Add Multiple Routes in Linux Using ip Command Examples

by Karthikeyan Sadhasivam on August 21, 2014

Apart from the default route, you can also configure additional routes.

For example, your server you might have 2 interfaces (eth0 and eth1). By default, all the traffic is routed through interface eth0 irrespective of what IP address you have configured on eth1.

To route the incoming and outgoing traffic through eth1, other than the default route (eth0), you also need to add additional routes for eth1 .
(more…)

15 aptitude Command Examples for Package Management in Linux

by Balakrishnan Mariyappan on August 11, 2014

For Debian based systems like Ubuntu, you can use aptitude command for package management from the command line.

This article explains several aptitude command examples including the following:

  • Install a specific version of a package
  • Install multiple packages using pattern
  • Search for a package using pattern
  • Get packages under a section
  • Don’t update a specific package (Using hold and keep)
  • Mark a package with a specific install type
  • Perform system update
  • Perform safe upgrade

(more…)

10 insserv Command Examples for Linux System Init Scripts

by Karthikeyan Sadhasivam on August 6, 2014

insserv command is used to control the start and stop order of the services that are on a Linux system.

It enables an installed system init script (boot script) by reading comment header of the init script and calculating the dependencies between all the scripts.

Insserv scans for the system facilities in the configuration file /etc/insserv.conf and the directory /etc/insserv.conf.d.
(more…)