The tc command in Linux can be used for fine-grained control over bandwidth throughput. In this case I have limited public outbound traffic to 50Mbps, and internal network traffic to 450Mbps. The syntax of tc is quite complex. So much so, I found a neat utility called ‘tcng’ (Traffic Control Next Generation) that interprits a […]
The Intel D945GCLF (Atom 230) main board has a serious bug in the Realtek gigabit NIC firmware. Any sustained transfer over 100Mbps will eventually cause the NIC to go offline until the network stack is reloaded or machine rebooted. I reproduced the issue in CentOS, Debian, and Windows. No driver fixes the issue; you have […]
Here’s a simple ‘skeleton’ script that will allow your Bash scripts to use a PID file, or ‘lockfile’. This ensures that only one instance can run at a time which is useful for daily Cron activities such as mirror updates. #!/bin/bash pidfile=/var/run/sync.pid if [ -e $pidfile ]; then pid=`cat $pidfile` if kill -0 &>1 > […]
If you aren’t storing critical system files on a partition, you can free up a ton of space. This will reduce the ‘reserved’ space on a Linux partition to 0%. I freed up 45Gb of ‘lost’ space on a 900Gb partition using the following command: tune2fs -m 0 /dev/sda4 Note: DO NOT set the reserved […]
I use the Unattended Project to deploy various Windows 2003 server versions via PXE. The following describes how to get Unattended Linuxboot (tftp or pxe boot method) to properly compile on a CentOS5 based Linux system. The CentOS machine was deployed with minimum software packages, so your mileage may vary depending on what you already […]
Foundry and Cisco both implement port grouping (load sharing) but are very different. The following code snippets describe the configuration needed between the two very different platforms to create a working Etherchannel trunk. On the Cisco, ports 23 and 24 form the group for port-channel1: port-channel load-balance src-dst-ip interface Port-channel1 switchport trunk encapsulation dot1q switchport […]
If it’s .tar.bz2, then you can use Code: tar xjvf cornbread.tar.bz2 to extract it all at once. If it’s just .bz2, then use Code: bunzip2 spankythefish.bz2
Twice now, I have had the (dis)pleasure of expanding our local storage on a couple of XenServer boxes. In a nutshell, here is how it works: 1. Expand physical disk (add more RAID members, ect). Use the procedure specific to your RAID card. 2. Use fdisk to expand the partition your Local Storage resides on: […]
One way to make your data legible is to apply cell shading to every other row in a range. Excel’s Conditional Formatting feature (available in Excel or later) makes this a simple task. Select the range that you want to format Choose Format, Conditional Formatting In the Conditional Formatting dialog box, select Formula Is from […]
Spammers love nothing more than launching dictionary attacks on unsuspecting domains using the ‘catch-all’ feature. This causes multiple problems — the main issues are excessive server load, disk usage, and spam volume. The worse issue is that once spammers catch on to the fact your domain has a catch-all, they will launch spam campaigns with […]