If running XenServer on a RAID array with writeback (controller cache) enabled and no battery backup, don’t lose power. If you do, you will discover the state.db is corrupt and XAPI fails to start. Everything is down, Dom0 lost it’s network config, you’re screwed. Maybe. This tutorial assumes you’ve got a metadata backup, all your […]
In a search to replace several NetGear WNCE2001 devices which had over time, proven themselves to be so unreliable they would literally kill entire wireless AND wired networks by randomly hijacking DHCP. I tried many devices — some either couldn’t bridge at all, others ‘worked’ but had such terrible range or connection quality they were […]
One-liner recursive grep + sed search and replace for php or other file types: grep “subject” * -rl –include=*.php | xargs sed -i -e ‘s/subject/replacement/g’
Recently I upgraded my remote office connection to 100Mbps (cable) and spent almost a month dealing with slow downloads over an openVPN client connection. Uploads were fine (maxing out the pipe) but downloads were 12-20 Mbps at best and fluctuating like crazy. TCP client mode actually performed better than UDP so I knew something was […]
I cooked up a Munin plugin for my Surfboard 6141 which monitors ALL available data from the status page. If you’re having intermittant signal issues and want to keep detailed data for cable technicians, this is for you! Check it out on Github: https://github.com/djamps/munin-surfboard6141
After facing issue after issue with Idera/R1soft’s PXE and CD-ROM boot media — specifically, ancient kernels which are unable to obtain network connectivity on modern hardware, I decided to roll my own PXE boot image including the R1soft agent and a few other tools with the latest Debian stable. It turned out to be easier […]
On a new XenServer deployment EXT storage is default. Although EXT is nice (ability to manipulate raw VHD files and use sparse storage), LVM is faster and more stable. Here is how to switch between storage modes (be sure to back up all data first, as this will wipe everything in the repo): Use ‘xe […]
From time to time the du command doesn’t match up with df. This is due to deleted files that are still held open by a process. You can total the deleted but ‘still open’ file usage: lsof | awk ‘/deleted/ {sum+=$7} END {print sum}’ Or, to simply list all the files and their processes: lsof […]
Find all possible root symlinks (leftover from attempted exploits) and save them as a list ‘symlinks.txt’. ls /var/cpanel/users | grep -v “\`\|\.\|cpanel\|root\|mysql\|nobody” | \ while read CPUSER; do find /home/$CPUSER -type l -not \( -lname “/home/$CPUSER/*” \ -o -lname “*rvsitebuilder*” -o -lname “[^/]*” -o -lname “/usr/local/apache/domlogs/*” \ -o -lname “/usr/local/urchin/*” \) ; done \ > […]
This tool will poll the output of command(s) or URL(s), and send email alerts if the output changes, contains (or not contains) certain text, or becomes unavailable. It’s a light weight, reliable monitoring replacement for the pile of garbage most RAID vendors include with their cards. Complex excludes and finds can be specified as Perl […]