KrazyWorks

Compress Old Log Files on Linux

Igor — Thu, 12 Jan 2012 22:06:20 +0000

Most log files located in /var/log are part of the log rotation and will be compressed automatically. However, in many cases various user applications maintain log files outside of /var/log. These logs are not managed ...

Testing SSH Connectivity to Multiple Servers

Igor — Tue, 27 Dec 2011 06:46:39 +0000

Posted in Commands & Shells

Imagine a hypothetical scenario: you support hundreds of remote servers and you need to check which server you can access via SSH and which servers are not letting you log in. Doing this manually is a tedious process that many sysadmins choose to skip. The inevitable outcome is inability to quickly access a system when it really counts.

Quick Review: Boxee Box

Igor — Tue, 27 Dec 2011 04:22:27 +0000

Posted in Featured Hardware

Some of the technical issues with Boxee Box could have been fixed if the dev team was paying more attention to addressing the bugs rather than adding "features" of dubious value. In the final analysis, for the price and ease of use, Boxee Box is the best in its class and price range. You just need to be mindful of its limitations and buy it in hope of future improvements to its usability.

Be a HERO and Help STOP SOPA Now!!

Igor — Fri, 23 Dec 2011 16:24:45 +0000

Posted in Videos

Photo Fun with iPhone 4S

Igor — Mon, 19 Dec 2011 07:16:35 +0000

Posted in Cell Phones Featured

As an avid amateur photographer I would like to have my dSLR with me at all times. And my collection of lenses. And filters. And tripods. But even if this was possible, I don't really want to be, say, sitting at a bar, looking like I just returned from a Serengeti safari. My iPhone will have to suffice and I'll just have to get more creative with the photos apps to fill in for the fancy equipment.

Disable Usage Information Sharing on iPhone

Igor — Mon, 19 Dec 2011 05:23:38 +0000

Posted in Cell Phones

Carrier IQ is software installed on your iPhone by Apple at the request of the service providers. This system utility collect detailed usage and location data on your phone and sends it to the service providers. Supposedly, this was done to improve quality of service. In reality, however, if any such improvement actually occurred, it was only a side-effect.

Writing a Linux Startup Script

Igor — Fri, 16 Dec 2011 06:11:47 +0000

Posted in Commands & Shells Featured

As basic as the task of creating a startup script may sound, even experienced sysadmins sometimes run into problems with having services start at the right time during the boot process or stop during the shutdown. Two major reasons for this: the procedure is a bit convoluted due to linking. Also, writing startup scripts is not something you have to do very often these days.

Photo Noise Reduction Apps for iPhone

Igor — Wed, 07 Dec 2011 07:59:53 +0000

Posted in Cell Phones Featured

In digital cameras, image noise (grain) is most pronounced in photos taken in low-light conditions without a flash. For such situations, the camera sets high ISO (light sensitivity of the image sensor) and a long exposure. A number of apps are available for the iPhone to reduce the appearance of grain. None of these apps are particularly impressive, especially when compared to specialized PC software. There is a good reason for this: digital noise reduction is a very CPU-intensive process that also requires a large amount of memory.

iPhone 4S HDR Performance

Igor — Tue, 08 Nov 2011 21:31:10 +0000

Posted in Cell Phones Featured

HDR - High Dynamic Range - photography is a method of achieving a degree of visual detail in highlights and shadows beyond what the camera's image sensor can record in a single exposure. The HDR processing usually involves combining two or more frames taken at different exposures. This is done on the computer or inside the camera itself. Human vision uses the HDR approach.

Fun with Call Forwarding

Igor — Tue, 01 Nov 2011 02:20:03 +0000

Posted in Cell Phones

Sometimes you don't want people to reach you on your phone, but you don't want to do something obvious, like turning the phone off. Because then they'll just leave you a message and you will still be expected to call back. Below is a list of phone number in various US area codes that you can use to forward your unwanted calls.

iPhone 4S: Photo Camera Performance

Igor — Mon, 17 Oct 2011 01:46:52 +0000

Posted in Cell Phones Featured

Here's our quick-and-dirty test of the new iPhone 4S 8-megapixel camera with LED flash and autofocus. For comparison, we took some of the same photos using a Canon G10 14.7-megapixel compact camera with a 28-140mm wide zoom lens. All photos have been corrected in Photoshop by a professional photographer to produce the best possible result for each camera. iPhone 4S was used in HDR mode.

Simple Host Monitoring with SSH

Igor — Fri, 23 Sep 2011 04:10:06 +0000

Posted in Monitoring

Sometimes you just need something very simple to monitor a server or an application on a temporary basis. A basic ping monitor is fine, but it will only tell you if a server is responding on the network. It will not tell you if there is some other problem on the system. The script below relies on passwordless SSH setup to periodically log into the monitored nodes and check on their health by executing a local or remote script.

Viewing “man” Pages in a Web Browser

Igor — Fri, 16 Sep 2011 04:43:16 +0000

Posted in Commands & Shells

The Unix "man" pages are an indispensable tool even for the most experienced of sysadmins. Unfortunately, in a terminal window the text may be hard to read and getting a hard copy to take with you down to the datacenter will really test your Unix skills. The following quick script will convert the "man" page of your choice into formatted text and open it in the Web browser.

Autorebooting Servers on Low or High Load

Igor — Wed, 14 Sep 2011 21:03:14 +0000

Posted in Commands & Shells

Recently I ran into a situation where I needed to reboot several HPC cluster compute nodes. A couple of systems were still running user jobs that I did not want to interrupt. I also didn't want to sit around and watch those jobs, as there was not way of telling how long they could take to complete. The solution was to write a short script that looks something like this...

Changing Process CPU Affinity on Linux

Igor — Tue, 13 Sep 2011 20:58:37 +0000

Posted in Performance

A common real-life scenario: on a multi-CPU system Oracle processed have taken over and the system has ground to a crawl. The average system load is in double-digits and even logging in takes several minutes. The possible root causes for the problem can range from inefficient SQL queries (the common problem) to insufficient system resources. But at this point you just need to make the system a bit more responsive, so you can start troubleshooting.

Adding LUNs to VXVM on Linux

Igor — Tue, 06 Sep 2011 18:03:30 +0000

Posted in Disks and Volumes Featured

The following is a brief overview of the process for adding LUNs to VXVM under Linux. In our example we have an RHEL 5 server with existing LUNs and VXVM volume groups. Two new LUNs with multipathing were allocated from SAN and need to be added to the system to grow one of the volumes and the corresponding filesystem.

Testing RAM in Linux

Igor — Fri, 02 Sep 2011 15:42:08 +0000

Posted in Commands & Shells Featured

A number of good and mostly free tools are available for testing RAM hardware. However, most of these applications are designed to operate in stand-alone mode that requires shutting down the OS. Still, tare a few ways to run memory integrity checks from inside the operating environment. Here we will look at using dd and memtester.

Red Hat: Changing Hostname and IP

Igor — Wed, 31 Aug 2011 17:47:35 +0000

Posted in Networking

Changing hostname and IP is frequently required when a server is being moved from testing or development to production. The process is a fairly simple one, but steps must be performed in a certain order to avoid complications.

Using Expect with SSH and Su

Igor — Mon, 29 Aug 2011 14:47:08 +0000

Posted in Commands & Shells

We have discussed using expect with sudo in an SSH session. Another common way to run commands on remote servers as root is to use the su - root command, where sudo is not configured. The trick to automating su operations using expect is to launch the su command with the spawn ssh command.

Enable Foreign Keyboard on iPhone

Igor — Tue, 16 Aug 2011 17:38:20 +0000

Posted in Cell Phones

This is a simple one, but people are always asking: how do I type in Russian, Swedish, Spanish, whatever on my iPhone? Go to Settings -> General -> International -> Keyboards -> Add New Keyboard -> select your language -> select Hardware Keyboard Layout (if applicable).

Moving Average with Excel and Shell Script

Igor — Thu, 11 Aug 2011 16:41:54 +0000

Posted in Commands & Shells

In this example we will show you how to calculate simple moving average using Excel and a shell script. As more data is added to the file, the shell script and the Excel formula will automatically use the specified number of the latest data points to calculate the moving average.

Configuring Passwordless SSH

Igor — Sat, 23 Jul 2011 15:02:39 +0000

Posted in Commands & Shells

Passwordless SSH works by pre-sharing public encryption keys. It is important to understand that setting up passwordless SSH opens your servers to certain security risks. A compromised user account on one server may allow the attacker to gain access to multiple systems on the network. Try to avoid using passwordless access for accounts with elevated privileges.