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Log Event Time Distribution (Part II)

November 11, 2015 – 2:30 am

Earlier I discussed a way to visualize frequency and distribution of messages in log files. Here’s a script to help you with that. Currently, the script works with two time formats: the one used in …

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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.


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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.

Commands & Shells »

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 gets me every time. I have various expect examples scattered throughout this site, so this is more of an attempt at organizing them. Read the full story »

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 contact 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 …

Oracle Sun SPARC Server Quick Configuration

October 20, 2015 – 6:03 pm

In the following example we’re using a SPARC T4-2. These systems ship from the manufacturer with pre-installed Solaris 11. After the system has been racked and connected to primary and ILO networks, the first step is to …

Detecting Sun ILOM with NMap

October 13, 2015 – 10:57 am

This is an oddball tech note: how to detect Sun ILOM interfaces on the network using nmap. I needed to connect to one of the Sun boxes that dropped off the network, but couldn’t remember …

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”:

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 …