Linux

This tutorial explains the process of building useful multi­-part commands piece by piece.

To build complex commands in the terminal, we need to understand piping. Piping is basically taking the output of one command and sending it to another command as input. This is done with the | (pipe) symbol.

Last month, a small project required me to repeatedly read similar XML files to provide test data for another program. I would have to do it so frequently that it would be annoying to have to download, save, parse and repeat. The basic requirements were:
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logstash-logoLogstash is an open source central log file management application.

You can collect logs from multiple servers, multiple applications, parse those logs, and store it in a central place. Once it is stored, you can use a web GUI to search for logs, drill-down on the logs, and generate various reports.

This tutorial will explain the fundamentals of logstash and everything you need to know on how to install and configure logstash on your system.
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7 Patch Command Examples to Apply Diff Patch Files in Linux

by Lakshmanan Ganapathy on December 2, 2014

When there is a security fix available for a particular software, we typically do a binary upgrade using the package management tools like yum or apt-get.

But, there might be situation where you have installed a software by compiling it from the source code.

In those situation, how do you apply the security fix to the software?

The answer is to download the security patch and apply it to the original source code and re-compile the software.

This tutorial explains how to create a patch file using diff, and apply it using patch command.
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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.
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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.
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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.
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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.
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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.
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