May 2011

7 Default OpenSSH Security Options You Should Change in /etc/ssh/sshd_config

by Ramesh Natarajan on May 23, 2011

OpenSSH options are controlled through the /etc/ssh/sshd_config file. This article explains the 7 default options in sshd_config file that you should change.

In sshd_config, the lines that start with # are comments. For those options that uses the default values, the sshd_config file contains a commented line with the option and its default value.

This makes it easier for us, as we can see the OpenSSH option name and the default value without having to lookup somewhere else.
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Linux File Systems: Ext2 vs Ext3 vs Ext4

by Ramesh Natarajan on May 16, 2011

ext2, ext3 and ext4 are all filesystems created for Linux. This article explains the following:

  • High level difference between these filesystems.
  • How to create these filesystems.
  • How to convert from one filesystem type to another.

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Cron Vs Anacron: How to Setup Anacron on Linux (With an Example)

by SathiyaMoorthy on May 10, 2011

Anacron is the cron for desktops and laptops.

Anacron does not expect the system to be running 24 x 7 like a server.

When you want a background job to be executed automatically on a machine that is not running 24 x 7, you should use anacron.

For example, if you have a backup script scheduled everyday at 11 PM as a regular cron job, and if your laptop is not up at 11 PM, your backup job will not be executed.

However, if you have the same job scheduled in anacron, you can be sure that it will be executed once the laptop come back up.
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10 iozone Examples for Disk I/O Performance Measurement on Linux

by Ramesh Natarajan on May 2, 2011

As we discussed in our Linux performance monitoring introduction article, measuring IO subsystem performance is very important.

If someone is complaining that a database (or any application) running on one server (with certain filesystem, or RAID configuration) is running faster than the same database or application running on another server, you might want to make sure that the performance at the disk level is same on both the server. You can use iozone for this situation.
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