Recently while working on some node or instance automation using RightScale I needed to have some extra iptables rules created automatically when a new node booted. Initially I was just trying to do this via iptables commands which I note below but it would never work. After digging through the logs I realized that the iptables commands created by RightScale for the ServerTemplate I was using flushed iptables at the very end of the boot process and thus wiped out the iptables entries created by the RightScript I had created. To accomplish permanent iptables entries for a RackSpace node via RightScale you need to output the iptables command to a file in the location where the boot process picks them up after flushing the current ruleset. Below I describe my first attempt followed by the correct way to have iptables entries picked up by RightScale.
As every one knows Alex and I do lots of work with Nvidia Graphics cards and CUDA password cracking. I recently encountered the following error when trying to boot Backtrack 4 Linux on our CUDA server. Below I explain the error and why it happens and how to fix it.
There are a couple useful utilities on Linux to test disk input/ouput.
Sequential Disk Access: hdparm
The hdparm command will test sequential disk access and can be used with the below command. Replace /dev/sda1 with the mounted disk you would like to test such as /dev/hda1.
- hdparm -t /dev/sda1
The results will output similar to the below.