Increase CentOS 7’s MTU

Ethernet interfaces normally use an MTU of 1500 bytes. I recently needed to increase the MTU use by the NICs on a point-to-point link to 9000 bytes in order to improve DRBD performance. This is sometimes referred to as enabling jumbo frames. In the past I’ve...

How to configure a BIND DNS Cache in CentOS 7

Introduction I recently configured a CentOS 7 server to run BIND as a DNS caching server. This post documents the process. Although I used CentOS 7, these instructions should be equally applicable to CentOS 5 through 7, and Red Hat Enterprise Linux 5 through 7. If you...

Reset the GroundWork Monitor 6.0 Password

The GroundWork Monitor is a simple way to deploy Nagios monitoring to networks. It does a great job of monitoring Linux servers, and anything that speaks SNMP. I recently needed to make some updates to a GroundWork Community Edition VM, and found myself in a situation...

Updating a Soekris net4511’s BIOS

I performed BIOS updates on a stack of Soekris net4511s and net4521s today. Here’s a quick-and-dirty howto for anyone who wants to do the same thing from a Linux host running minicom. Note that these instructions should work on any net45xx series Soekris board,...

Directadmin and “Error Parsing Cron File”

I migrated my web hosting servers from cPanel to Directadmin earlier this year. The transition was smooth for the most part, but one problem was that users with blank crontabs with cPanel had corrupted crontabs post-migration. They could ssh in, and issue crontab -e,...

Logging into a VMware Server stuck on the “Loading…” Page

VMware Server is a handy app to run in places where server virtualization is needed, but you can’t justify the expense or effort required to setup a VMware ESXi or Xen host. One of the reoccurring problems that I run into, even on lightly loaded servers is when...

Joining the ACM – A Linux Sysadmin’s Perpective

The ACM, or the Association of Computing Machinery describes itself as “the world’s largest educational and scientific computing society”. Until recently, I assumed that since I was out of academia, and focused more on things that sysadmins do, like...

Installing Linux using a serial console

Just a quick note on the command to use to start up a RHEL / CentOS 5.x install from the serial console. This can come in handy if you’re using a modem and serial port for out of band management, and the need to conduct a remote reinstall arises. These settings...

vsftpd's “500 OOPS: cannot change directory” error

I recently installed a vsftpd FTP server on a CentOS Linux 5.2 box. After changing the FTP user’s home directory, I received the following error message every time I attempted to login as ftp: 500 OOPS: cannot change directory500 OOPS: child died Permissions...

Resuming failed Firefox downloads

Firefox’s download manager doesn’t have a built-in mechanism for resuming failed downloads. My Internet connection was cut off just long enough this morning for a Firefox download of an ISO image to fail. To resume the download, I used the wget command,...