Featured »

March 2, 2022 – 2:00 pm

Books have been written on the subject of awk and sed. Here’s a small sample of commands I put together over the years that are useful for everyday system administration tasks. Most of these tasks …

Read the full story »
Networking

Unix and Linux network configuration. Multiple network interfaces. Bridged NICs. High-availability network configurations.

Applications

Reviews of latest Unix and Linux software. Helpful tips for application support admins. Automating application support.

Data

Disk partitioning, filesystems, directories, and files. Volume management, logical volumes, HA filesystems. Backups and disaster recovery.

Monitoring

Distributed server monitoring. Server performance and capacity planning. Monitoring applications, network status and user activity.

Commands & Shells

Cool Unix shell commands and options. Command-line tools and application. Things every Unix sysadmin needs to know.

Home » Archive by Month

Article Archive for May 2011

Disabling WordPress X-FRAME-OPTIONS Support

May 30, 2011 – 3:37 pm

Staring with version 3.1.3, WordPress introduced X-FRAME-OPTIONS support for the admin and login pages. This is a simple defensive measure against sneaky characters trying to encapsulate your blog within their own Web sites using iframes. So this new security was a welcome addition to WP for most users. I was not one of those users.

Password-less SSH and Autofs

May 15, 2011 – 4:04 am
Computer Password Security

Recently I’ve ran into an unusual problem with SSH on SLES 11 SP1. The system – a small HPC cluster – is configured to use NIS for authentication and automounter maps. Whenever a user logs in, the home directory is automounted from an external NAS. Each user has a ~/.ssh directory with the authorized_keys2 and known_hosts required for password-less SSH access among the cluster nodes.

Troubleshooting InfiniBand Connections

May 4, 2011 – 10:36 am
network_cable_01

The following is a brief troubleshooting guide for an InfiniBand network found in common HPC Linux clusters. Running these commands requires OFED 1.5.2 or later package installed on your systems. Additionally, the “pdsh” (parallel shell) command is part of the HP CMU cluster management software (version 4.2.1 used in our example) installed on the head node.