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.
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Tags:
--dport,
/etc/iptables.d,
accept,
CentOS,
cloud,
input,
instance,
iptables,
Linux,
node,
port,
protocol,
rackspace,
rightscale,
rightscript,
rules,
servertemplate
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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.
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Tags:
*32,
/dev/nvidia,
256,
64,
backtrack,
Blogroll,
cuda-multiforcer,
device,
file,
input,
output
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I needed a simple way to require data in a form field before it could be submitted. There are chunks of JavaScript code all of the Internet that allow you to do this easily so I selected one and added it to my form with ease. One small issue I had was it required that the name attribute be modified for it to work which caused an issue with the application I was adding it to. The issue was the name attribute was modified thus it would not save the data to the proper database table column. Below I explain how to add this bit of JavaScript to your form and modify your form for it to function properly.
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Tags:
.js,
alt,
element,
form,
function,
input,
Javascript,
name,
onclick,
require,
submit,
tag
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Posted by alex in Insights
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.
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Tags:
.pgpass,
disk,
hard disk,
hda1,
hdparm,
input,
iostat,
output,
random,
reads,
sda1,
seeker,
sequential,
sysstat,
writes
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