Featured »


Finding Prime Numbers

April 22, 2016 – 2:09 pm

I have no intention of competing with GIMPS. To me this is a fun scripting exercise that may produce useful results beyond this initial application. Our goal is to take a bunch of integers and …

Read the full story »

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.

Security »

Increasing Entropy Pool in Linux

June 28, 2016 – 9:48 pm

The pool of random numbers in Linux is derived primarily from user interaction (keystrokes and mouse movement). A server does not have such a source and the random pool may start running low, especially during periods of low system activity. This negatively affects security of many system services that use cryptography, making them more predictable. Read the full story »

Fixing NIC Name in Cloned VMWare Linux Machines

June 28, 2016 – 12:32 pm
network switch

A suspected bug with certain versions of VMware ESX causes cloned Linux VMs to obtain a sequentially-number NIC. For example, if the parent VM had eth0, the clone will have eth1, and the clone of …

Better ‘date’ Functionality in Solaris

June 28, 2016 – 8:53 am

The Solaris date command does not have many of the useful features of its GNU equivalent. A workaround is to use Tcl. This requires tclsh to be installed (which tclsh). You can implement this workaround as …

Create NFS share from QNAP CLI

June 13, 2016 – 2:21 pm

In this example we create the “test” NFS share on a QNAP NAS from CLI and export it to client_ip_01 and client_ip_02. Things to keep in mind: this only creates an NFS share – not …

Speed Up Shell Loops Using Arrays

June 7, 2016 – 9:02 am

Just a quick note on addressing a common issue of running redundant commands when using shell loops. Let’s say you needed to get a count of network connections to an Oracle database server for each connection …

Kodi Volume Control Stops Working

May 22, 2016 – 1:01 am

All of a sudden, when using the remote (either radio or IR), Kodi sound controls stop responding. The volume level does not change and the mute button doesn’t work. These are possible symptoms of an …

VMWare VMDK Locked Error

May 21, 2016 – 10:27 pm

So, being a Unix admin on-call for the week, I just spent half of my Saturday fixing a dead Windows VM. Very annoying. The best I can tell, the issue occurred during the snapshot operation. …

Decrypting Mac Disk

May 20, 2016 – 11:41 am

It is generally a good idea to use full-disk encryption, especially on a laptop. However, this becomes bothersome if you are trying to re-partition your disk, say, to make the system dual-boot. Here’s a quick …

Useful Bash One-Liners

May 2, 2016 – 8:43 am

Here’s a  loosely-organized pile ‘o shell quickies I kept googling now and then and finally decided to write ’em down.

Monitoring NetBackup Daemons

April 27, 2016 – 9:25 pm
tape dlt backup

Here’s an example of a script you can use to monitor NetBackup server daemons in a Linux environment. The main difficulty with keeping track of these services is that there are so many of them. …

Using JTR to Crack Office Documents

April 22, 2016 – 5:35 pm
Macro computer screen shot with binary code and password tex, great concept for computer, technology  and online security.

John the Ripper is a free multi-platform password-cracking software. This article is not intended to be a comprehensive guide to jtr, rather a quick how-to. Starting with version 1.7.9, jumbo patch 6, jtr supports password …

Counting Beer Calories

February 24, 2016 – 10:58 pm

Calories in beer come mainly from alcohol, unfermented sugar, and residual yeast. You’ve heard of the beer belly, but there’s nothing special about beer calories. A bottle of Heineken (150 calories) won’t make you any …

Monitoring Application Network Connections

February 11, 2016 – 3:12 pm
network switch

A Java application on one of my servers has been causing problems by opening up too many network connections and now closing them quickly enough. I needed to be notified when the number of connections …

Run Cron Jobs at Arbitrary Intervals

January 27, 2016 – 10:24 am
time clock watch

Current versions of cron support sophisticated syntax making creating weird schedules a breeze. With older versions of cron you normally had to schedule multiple jobs to fill every time slot in a complex schedule. The …

Diff on Output of Remote Commands

January 25, 2016 – 1:47 pm

Let’s say you run the same command on two remote servers and you want to compare the output. Here’s a quick example:

Show NIC Bandwidth Utilization

January 15, 2016 – 12:43 am
network switch

Just a quick script that will measure bandwidth utilization in KB/s for all NICs on your server over the specified period of time. You can call the script with an optional time wait parameter in seconds.

Find + Rsync + Xargs

December 22, 2015 – 11:09 am

Just some quick syntax for running multiple rsync threads in parallel using find and xargs. In many cases (especially if NFS is involved)  this can greatly speed up the copy operation.

Taking Linux Temperature

December 14, 2015 – 12:21 am

Just some notes on setting up temperature monitoring and alerting on CentOS/RHEL running on HP ProLiant. The first step is to install lm_sensors:

Bash and Expect Snippets

November 25, 2015 – 1:12 pm

A small collection of maybe helpful examples of how to use expect with Bash. This is a very useful tool, especially when writing a better script is just too much work, but the funky syntax …

Deleting Lots of Files Quickly

November 17, 2015 – 9:03 am

I am not talking about hundreds or thousands of files. I am talking about hundreds of thousands. The usual “/bin/rm -rf *” may work, but will take a while. Or it may fail with the …

When Was that Server Built?

November 11, 2015 – 11:49 am

Just a quick note on how to (sort of) figure out when a server first came online. This can be useful to various folks in your bean-counting department working on maintenance contract renewals and whatnot. …

Testing Email Server Response

November 7, 2015 – 5:37 pm
colorful shells

A little while ago I ran into a situation when connections to the relay email server would occasionally time out. The issue seemed sporadic resulting in a controversy regarding its source. The perimeter email server …

Tuesday Morning Rant

October 27, 2015 – 11:27 am

So I just got around to installing CentOS 7. What a pile of shit with bugs all over it. The installation GUI completely messed up network configuration. On the first try, the network config I …