Author Archives: Randy

Limiting Bandwidth in Linux

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 […]

Intel D945GCLF Ethernet timeouts; firmware bug

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 […]

Lockfiles in Bash

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/ if [ -e $pidfile ]; then pid=`cat $pidfile` if kill -0 &>1 > […]

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Reclaim ‘missing’ space on a Linux partition with tune2fs

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 […]

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Etherchannel 802.1q trunk between Cisco and Foundry

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 […]

Alternate Row Shading in Excel

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 […]

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Cpanel – Globally disabling the Email Catch-All feature

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 […]

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