KrazyWorks

Installing Ganglia on RHEL

March 21, 2011 – 2:59 pm

This is a quick follow-up to my earlier post about installing Ganglia from source on SLES. Here we will install Ganglia from precompiled RPMs on an RHEL server. The basic cluster setup for this example remains the same: two clusters: CLUSTER1 and CLUSTER2 with head nodes head_node1 and head_node2

Opening Custom Ports in SuSE Firewall

March 4, 2011 – 2:18 pm

Most of the servers I work with are already behind an enterprise firewall, so I rarely get to configure a software firewall. In the following example, I installed Webmin and Usermin on a SLES 11 server that had SuSE firewall enabled. Webmin and Usermin by default use ports 10000 and 20000, respectively. These ports are not in the list of common services you would find in the SuSE firewall configuration GUI. There are a couple of ways of adding custom ports to the list of the allowed services.

Force NTP Time Update on Linux

February 21, 2011 – 8:36 pm

Imagine this: you created the /etc/ntp.conf file, enabled and started the ntpd service, and… the system time is still off. Is there a way to force time sync with the NTP server? It must be your lucky day. All you have to do is to connect to your box as root and run the following command…

Don’t Be Afraid to Reboot Unix Servers

February 21, 2011 – 8:11 pm

Reboot your Unix servers after making any major changes to the production environment. Should an unexpected problem come up, it will be easier to deal with it when everything is still fresh in your mind and not six months down the road, when you have to do a reboot to replace a failed system board and suddenly discover that some application wouldn’t load, by which time you forgot all about this application and have to start with the first page of the admin guide.

Fixing Your Crappy Cell Phone Photos

February 10, 2011 – 10:11 pm

Some of today’s cell phones feature camera resolution that rivals digital SLRs from two year ago. An 8-megapixel cell phone camera is no longer a novelty. Unfortunately, high resolution is the only good thing cell phone cameras have to offer and it does not translate into better pictures. If you compare photos taken with the most advanced cell phone camera to those taken with a $200 point-and-shoot digital camera, the cell phone invariably loses.

Find Command with Multiple Exec Statements

February 10, 2011 – 12:32 am

This is a very simple one, but somehow I always forget the correct syntax. I want to use the “find” command to locate files and then use several “exec” statements to perform various operations on whatever “find” finds. In the following example I am making sure that all /etc/*.conf files are owned by root and that they don’t have permissions greater than 644.

WordPress 3.0.4 – the Return of the Custom Field Bug

January 31, 2011 – 4:20 pm

After upgrading to the latest stable WordPress version 3.0.4 I ran into an old issue I haven’t see for almost two years. Clicking “Publish” or “Save Draft” when writing a new post seems to remove some custom fields. If you re-add the custom field and click “Update”, the entry stays. But it goes away again once you use the “Save Draft” or “Publish”.

LPI Invents Linux Commands

January 18, 2011 – 7:50 pm

It would appear that in order to obtain Linux Professional Institute’s LPIC-2 certification, one needs to know real Linux commands as well as imaginary ones. On the Sample Questions page for LPIC-2 Exam 2 the LPI Linux gurus pose the following question

iPhone OS 4 Upgrade: One Month Later

October 13, 2010 – 1:36 am

Over a month has passed since I upgraded my iPhone 3Gs to OS 4. There are a couple of significant issues that I noticed. First, the battery life – not particularly impressive to begin with – got shorter. Before I used to get through the day on one charge. I only charged my iPhone overnight. Now, in addition to the nightly charge, I find I need to use the car charger on the way from work to keep the iPhone alive. Since there have been no changes in how I use my iPhone, I have to assume OS 4 causes iPhone to consume more power.

Windows 7 Black Screen After Booting

October 5, 2010 – 4:07 am

I had to power-cycle my Windows 7 64-bit laptop. The bootup sequence looked normal and reached a point where I could see the black screen with the mouse cursor. After this stage my desktop would usually appears, but not this time. I could move the mouse and I could even establish a remote desktop connection to my laptop. But I could not log in. Every time it would reach the same point – the black screen with the mouse cursor – and it would stop.

Modifying Solaris Services

September 9, 2010 – 4:33 pm

Recently I ran into an issue: the sshd service on a Solaris 10 box needed to be used with a custom configuration file. By default, the sshd service will use /etc/ssh/sshd_config. I needed it to use /etc/ssh/sshd_config_custom. I could not just modify the default configuration file. Don’t ask why – it’s complicated. So here’s what I ended up doing and this process is applicable to modifying any other Solaris 10 (and above) service.

Substitute Commands Depending on User ID

September 9, 2010 – 2:44 pm

Here is a quick example of how to substitute system commands based on who tries to run them. A customer of mine has recently deployed a security audit application on his servers. The application has a few bugs that the vendor has not yet resolved. For example, the security audit agent looks at the output of the “mount” command to see if any filesystems are mounted without the “nosuid” option.

iPhone 3GS OS4 Upgrade

September 4, 2010 – 5:23 pm

iTunes for Windows must be one of the buggiest, most poorly written applications out there. In terms of wasted months of your life it definitely ranks up there with Lotus Notes and Media Player 12. I don’t know how well iTunes works on a Mac (I like computer mice with twenty buttons, so I never was a big Mac fan), but I think I read somewhere that iTunes for Windows is the leading cause of suicides among iPhone owners.

NFS “Not Owner” Error

August 30, 2010 – 11:34 pm

The “not owner” error is displayed on the client system (usually Solaris) when attempting to mount an NFS share from a server. This error may appear even though the share is correctly exported and the client system has full access. If you are getting a “permission denied” error, then this article is not for you and you should check here instead.

WordPress 3.0 and 3.0.1 Upgrade Bug

August 23, 2010 – 4:01 pm

Ignoring my own advice to never install latest WordPress releases as soon as they come out, I upgraded my installation to WP 3.0 and shortly after to 3.0.1. Doing so broke a few things. Automatic plugin updates or installs seem to hang and so does automatic WordPress upgrade. Let me illustrate. According to this screenshot, I need to update one of the plugins.

Gadget Review: D-Link DNS-321 NAS

August 1, 2010 – 10:51 am

The D-Link DNS-321 is among the least expensive dual-disk RAID NAS systems currently on the market. This small device offers an impressive array of features such as FTP, Samba, NFS, iTunes, DHCP, HTTP and UPnP …

Gadget Review: Sony PRS-900 eBook Reader

April 26, 2010 – 3:37 am

I have a ton of technical documentation in PDF format. Sometimes I need to browse this collection to find some specific piece of information. In other cases I may need to read an entire book …

Book Review: CompTIA Linux+ Certification Study Guide

March 29, 2010 – 4:06 pm

For all of you hungry certification seekers, today on the menu we have Brian Barber’s CompTIA Linux+ Certification Study Guide. The CompTIA Linux+ certification, as you may or may not know, is designed for novice sysadmins with six to twelve months of Linux experience.

Server and Network Monitoring with iPhone

February 25, 2010 – 6:53 pm

What is a Unix sysadmin doing with an iPhone, you ask? It was a birthday present, if that’s all right with you. I know, I should have gotten something odd with a beta version of …

How to Really Kill Computer Viruses

February 21, 2010 – 6:34 am

How do you know if your computer has a virus? Is it connected to the Internet? Then it has a virus. Many computer viruses and other malicious applications are very resilient and will actively resist any attempts to deactivate and remove them. Some viruses can even delete your antivirus application or prevent it from working properly. Many viruses cannot be effectively removed once they are loaded in memory and active.

Forcing Linux to Reboot

January 29, 2010 – 3:21 pm

Until I branched out a few years ago from supporting Unix server to working with Linux clusters, I never really encountered this issue: you type “reboot”, “init 0”, or “shutdown” as root and… nothing happens. Or the system starts going down but then hangs on unmounting a filesystem or unloading a module. I think this happened once to a colleague of mine who was rebooting a Solaris server, but this is a common problem with Linux.

Upgrading from Vista to Windows 7

January 27, 2010 – 10:45 pm

Recently I upgraded a client’s Vista computer (Toshiba Qosmio, 4Gb, Intel Core Duo P7350, 7200-RPM 200-Gb disk) from Vista Ultimate 64-bit to Windows 7 Ultimate 64-bit. Being a Unix sysadmin this is not something I usually do. How did the experience compare to upgrading HP-UX, Solaris or SLES? In a nutshell: I’d rather walk around all day in wet underwear than attempt to upgrade Vista ever again.

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