![8vl3onvznkopxa6ny9995yrc4gw[1]](https://i0.wp.com/www.krazyworks.com/wp-content/uploads/2021/10/8vl3onvznkopxa6ny9995yrc4gw1-175x150.jpg "Awk & sed Snippets for SysAdmins")
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openlava Quick Test
After years working with PBS and LSF, ran into Jeff Layton’s “Share the Load” review of openlava resource manager in the Feb 2013 issue of the Admin Magazine and nostalgia took over. So I built …
Jailbreaking My iPhone 4S
An iPhone 4S is a fairly sophisticated computer capable of doing many interesting things. Unfortunately, since most phone users are computer idiots, to preserve its bottom line and the sanity of its tech support staff, Apple imposes severe limitations on what you, as a user, can do with your iPhone or iPad. As a Unix sysadmin I am entirely on Apple’s side on this one. However, it would have been nice if Apple allowed an option of full access in exchange for voluntarily voiding the warranty. For those of us who know what they are doing and are not gonna run in tears to the nearest Genius Bar if something goes wrong…
Remounting Active NFS Filesystems
Here’s a scenario: you have an NFS client mounting a filesystem from server1. You need to migrate this data to NFS server2 and remount the filesystem from the client to point to the new server. The problem is that there is a user application on the client system that uses the NFS mount, preventing you from unmounting it.
Quick BTRFS Test on OpenSuse 12.2
The recent announcement from Suse Enterprise Linux that Btrfs was production-ready raised some suspicions. The last time I tested btrfs (not very long ago) the primary issues were excessive CPU utilization and filesystem space that seemed to disappear into nowhere. So, as a quick test, I put together an OpenSuse 12.2 (3.4.6-2.10-desktop, OpenSuse 12.2) 64-bit VM (ESX) with one dual-core vCPUs, 4GB RAM, the OS disk and a 6GB striped LVM filesystem consisting of 4 4-GB virtual disks.
Healthy Lifestyle
If you Google something along the lines of “make rsync faster”, the most common thing you’ll see is people saying “hey, I have a gigabit network connection and my rsync is crawling along at a hundred kilobytes per second.” Well, the issue here is not the network. Rsync needs time to analyze source and destination, generate checksums and compare timestamps, build a list of stuff to transfer and then, finally, start the copy process, one item at a time. You see the problem, I am sure.
Searching Large Network-Mounted Filesystems
Recently I ran into a small problem: I needed to find recently-modified files in a very large NFS filesystem. One of the high-level folders contained dozens of sub-folders with thousands of files in each. There is a significant performance penalty associated with placing such directory structures on network-mounted filesystems. Running the “find” command at the top of the filesystem would have taken over an hour and the problem here was not available bandwidth, but the time it takes for the “find” to request and receive attribute information for each folder and file.
Linux LVM: Reduce Filesystem and Logical Volume
The following example shows how to reduce the size of a filesystem mounted on an LVM logical volume. The instructions below are only for non-root filesystems. No reboot is required, but the filesystem will need to be unmounted. So, if there are any user applications using this filesystem, they will need to be stopped and the users will need to log out.
Playing With Time in Bash Shell
The “date” command in Bash shell offers a remarkable array of features that can be very useful in performing many system administration tasks. As you will see below, it is easy to determine date, time, day of week for any interval of time. This can be very useful for system automation tasks with “cron” and “at”.
Quick Review: Boxee Box
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.
Photo Fun with iPhone 4S
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.
Writing a Linux Startup Script
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
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
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.
iPhone 4S: Photo Camera Performance
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.
Adding LUNs to VXVM on Linux
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
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.
D-Link DNS-320 NAS Review
In the past I reviewed the DNS-321 and the major complaint there was the device’s inability to utilize gigabit network capacity due to severe memory and CPU restrictions. While the DNS-321 was initially built as a 100-Mbit NAS and later converted to gigabit, the DNS-320 was built as a gigabit-capable storage device from the very beginning. It is still a very flimsy-looking plastic box filled with cheap components. If I am lucky, it may run for a year or two before the cooling fan fails or the power supply burns out.
Microsoft Launches Office 365. Fails.
To much fanfare Microsoft launched its first “cloud” version of the Office – the Office 365. Silly name, I know, but I still decided to give it a shot. Call me an optimist, but sometimes I feel there is a chance Microsoft will come out with a product more useful than Xbox 360. For the sake of brevity, let me just say that Office 365 was not that product. I can’t really tell you how good or bad it is, because I never got past the convoluted installation procedure. My many years of experience as a sysadmin did not help.
Facebook Security for the Lazy
Every time you use Facebook, you probably have a nagging feeling in the back of your head that someone other than your friends is reading your posts. You should trust that feeling. At the same time, keep in mind that Facebook is a tool designed primarily for sharing personal information with large groups of people you barely know. Facebook is not your personal diary or a substitute for SMS. You just need to assume that everything you post on Facebook inevitably will end up in the hands of someone you don’t like very much. And then you proceed based on that assumption.
Useful iPhone Apps
Useful iPhone apps? Really? Yeah, there are a few. These may not be the best-written apps, or the easiest to use, or the most aesthetically appealing, but they perform a function that benefits your bottom line. And what else can you want from computer software if not that? So let me get started in no particular order.
Don’t Be Afraid to Reboot Unix Servers
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.
iPhone OS 4 Upgrade: One Month Later
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.
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![DSCF5361[1]](https://i1.wp.com/www.krazyworks.com/wp-content/uploads/2020/10/DSCF53611-80x80.jpg "Processing Videos with ffmpeg and Lightroom")
![Cat-Devouring-A-Bird-Pablo-Picasso[1]](https://i0.wp.com/www.krazyworks.com/wp-content/uploads/2020/10/Cat-Devouring-A-Bird-Pablo-Picasso1-80x80.jpg "Searching Twitter")
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![iwoau71okwxqh4jv3k4ook32qps[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/08/iwoau71okwxqh4jv3k4ook32qps1-80x80.jpg "Finding Cron Jobs")
![5gtysva4wkc8mzc1k3e66vaycxx[1]](https://i1.wp.com/www.krazyworks.com/wp-content/uploads/2021/08/5gtysva4wkc8mzc1k3e66vaycxx1-80x80.jpg "Understanding Memory Utilization in Linux")
![sy2zeb1vp2h8itlxfbbylw0jrm0[1]](https://i0.wp.com/www.krazyworks.com/wp-content/uploads/2019/12/sy2zeb1vp2h8itlxfbbylw0jrm01-80x80.jpg "Validating HTTPS Cache Peers for Squid")
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