Articles in Featured
The vCenter Standalone Converter is a handy app you can run on your Windows or Linux PC to to P2V a remote server. As convenient as the Converter is, there are a few gotchas that …
If you have passwordless SSH configured on multiple servers, it’s a good idea to verify your access from time to time. This task may get rather tedious with a large number of remote systems. The simple script below will cycle through a list of servers and make sure you can access them without being prompted for a password. Any failures will be saved in the CSV file for later analysis.
This is a quick reminder on how to configure a Celerra filesystem for dual NFS/CIFS access where Windows-side permissions would translate correctly to the NFS side. By default, Celerra datamover will mount filesystems in “Native” mode. In this case, a file or folder created by a Windows user via the CIFS share will take on the default Unix permissions on the NFS side: 755 for folders and 644 for files.
Filled up filesystems is a recurring condition eating up sysadmin time on a regular basis. Some studies show that filesystems running out of space are responsible for most day-to-day issues handled by IT departments. Disk …
As we all know, Celerra and its kin can get a bit annoying with their “filesystem over 90%” warning emails. Enabling the “autoextend” feature for the filesystems is one option, but if you are a control …
In the past few days my Postfix server has been having occasional problems talking to the mail gateway. They problem would come and go. The Postfix server would timeout trying to connect to the gateway and keep …
Imagine you have an HPC cluster with a hundred compute nodes named node001-node100. The two commands below will help you generate a list of node names – either all name on one line or one name per …
A small but potentially annoying problem: on rare occasions, your iPhone/iPad may decide your calendar looks full enough and will stop syncing with your Google calendar. This is a situation where:
Calendar sync between your iDevice and …
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 …
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.
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.
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.
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.
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.
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”.
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.
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.
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.
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.
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.
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.
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.