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Create ISO Images

October 2, 2015 – 5:56 pm

The genisoimage has been around for a few years, but is relatively little-known. It is is a pre-mastering program to generate ISO9660/Joliet/HFS hybrid filesystems and is particularly good for creating portable data backups. Here are a …

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Unix and Linux network configuration. Multiple network interfaces. Bridged NICs. High-availability network configurations.


Reviews of latest Unix and Linux software. Helpful tips for application support admins. Automating application support.


Disk partitioning, filesystems, directories, and files. Volume management, logical volumes, HA filesystems. Backups and disaster recovery.


Distributed server monitoring. Server performance and capacity planning. Monitoring applications, network status and user activity.

Commands & Shells

Cool Unix shell commands and options. Command-line tools and application. Things every Unix sysadmin needs to know.

Processes »

Upping the Soft nproc Limit

October 5, 2015 – 11:12 am

This is just a quick note to myself about increasing the “soft nproc” value. On one of the RHEL 6 Tomcat servers I got the following error when trying to “su – tomcat”: Read the full story »

Hold Off on iOS 9 iPhone Upgrade

September 21, 2015 – 2:16 pm

If you haven’t updated your iPhone 6/6 Plus to the recently-released iOS 9, I’d suggest you hold off for a few weeks. Several bugs – including a significant security hole – have surfaced that will …

Removing Metadata from Images

September 8, 2015 – 12:09 pm
binoculars watch security rifle gun

Phones and cameras record a surprising amount of personally-sensitive information with the photos they create. This data includes timestamps, GPS coordinates, software used to process the images and lots of other details you may not …

Reduce SNMPd Logging Level

September 8, 2015 – 11:01 am

By default, (on RHEL/CentOS, at least) snmpd will log all connection attempts, which can turn your /var/log/messages into a giant mess, looking something like this…

Arthemia jCarousel Number of Posts

September 4, 2015 – 3:45 am

This is primarily just a note to myself on how to change the number of visible items in the jCarousel implementation for the WordPress Arthemia theme. Recently I finally updated to the current version and …

Tuesday Night Rant: LED Light Bulbs

September 1, 2015 – 9:51 pm
Row of light bulbs

An off-topic for sure, but after a brief conversation about LED bulbs with a friend – an electrician – I found I had more arguments then I was willing to spill on Facebook. I am …

Collectl & Colplot Sytem Performance Analysis Tools

August 26, 2015 – 11:17 am

It is not often that I run into Unix performance analysis tool that, a), I haven’t seen before and, b), is worth my attention. Collectl is both. It is a very useful combination of iostat, …

Installing Perl Modules with YUM

August 17, 2015 – 5:30 pm

Just a quick note on how to install Perl modules with YUM. Due to differences in the naming conventions, YUM package name for a Perl module may differ from the the module’s native name in …

Brief Guide to PDSh

August 17, 2015 – 12:53 pm

PDSh (Parallel Distributed Shell) is a high-performance parallel remote shell utility allowing you to execute commands on multiple remote hosts simultaneously. The utility was originally developed by LLNL and is currently available under GNU CPLv2. …

Find Available IP Addresses

June 18, 2015 – 10:58 am

After a while, available IP addresses on the subnet may become hard to come by. Whatever spreadsheet you used to track IP allocations is likely out of date. Here’s a simple script that will scan …

Multi-Cluster Ganglia Configuration

June 17, 2015 – 11:28 am

I’ve discussed Ganglia configuration and RHEL/CentOS installation in the past. The usual structure is where every node belongs to one cluster. Recently I ran into a requirement to have nodes assigned to more than one cluster. …

Enabling dmesg Timestamps in RHEL

June 12, 2015 – 5:04 pm

By default, CentOS/RHEL dmesg timestamps are disabled. Here are the instructions to enable timestamps and a quick script to display time in a human-readable format.

Raspberry Pi 2 OpenELEC Player

June 10, 2015 – 4:37 pm

Just some quick documentation, mostly for myself, but feel free to try. This is a Raspberry Pi 2 with OpenELEC. The design is intended for overclocking, good wireless performance, and convenience of dual remotes. This …

Saving Postfix Messages

June 3, 2015 – 3:08 pm

Sometimes for testing purposes you need to save all messages going through Postfix active queue. There are a couple of ways of doing this.

Detecting Synology NAS with nmap

May 29, 2015 – 3:07 pm

Just a quick note for myself on how to find Synology NAS servers on the network without having to use the bulky Windows utility that ships with these systems.

Dealing With Prolific Emailers

May 26, 2015 – 2:39 pm

So you come back from vacation, open Outlook and see thousands of unread emails. Who sends all this stuff? There’s an easy way to identify the sources of this background noise. In Outlook’s inbox, select …

BASH History Control

May 12, 2015 – 12:01 pm

The standard output of the “history” command will show you the last one thousand commands executed by the user. This is useful, of course, but there are a few issues. Sometimes it’s important to know …

Verify Email SSL Certificate from CLI

May 8, 2015 – 10:36 am

Just a quick reference for validating SSL certs on mail servers. This is not something I have to do often, but when the need arises, I find myself googling the answer every single time. So …

Extending Swap on LVM2 Logical Volume

May 7, 2015 – 11:16 am

To grow swap on LVM you will need to temporarily disable the swap LV. This will leave without swap space, which may upset some applications (Oracle). So the first step should be to set up …

Faking the Uptime in Linux

May 4, 2015 – 10:05 pm

If, for whatever reason, you need to fake the Linux server uptime, there is a hacked kernel module you can use. The instructions are below.

Resetting HP ILO from OS

May 4, 2015 – 11:02 am

You can use ipmitool package in Linux to reset your HP server’s ILO password. The basic instructions are below.

Removing CTRL-M from Unix Files

April 16, 2015 – 4:44 pm

This is a simple but annoying and persistent problem: text files edited on Windows and the uploaded to Unix acquire the “^M” character at the end of each line. In my experience, this little problem …

Observium Agent Installation on Pidora

April 13, 2015 – 11:50 am

Just some quick notes on installing Observium agent on Raspberry Pi running Pidora. Pretty much the same process applies to any Fedora-like flavor.