A particular nasty local denial of service attack is a fork bomb. It's dead simple: A program just replicate itself, which again replicate itself and so on until all resources are exhausted. Fortunately, protection against fork bombs are easy - but rarely used at all.

RHEL provides a crash dump facility called netdump (network crashdump = netdump). Traditionally UNIX writes the kernel dump to the swap partition. A classical crash dump facility first need to recover the dump before it's reused as swap. Other crash dump facilities enables kernel dumps to be written to disk. Diskdump is such a facility. However, great care must be taken as to not overwrite important data on the file system. Netdump solves that by writing the kernel dump to the network destined to a netdump server.

SysRq (System Request) is probably one of those keys on your keyboard that you rarely use. On Linux, you can use it to perform system functions if the system becomes unresponsive. You can sync disks, reboot or crash the kernel if that is what you want.

Linpro held the annual "Linuxdagen" ("Linuxday") 7. May 2007. It was the usual mix of interesting and not so interesting presentations. There was a lot more people attending this year than last year - which was great. My presentation about SELinux dealt with how SELinux enforces "mandatory access control" (MAC) instead of the traditional "discretional access control" (DAC) on Linux. Handout can be found here (norwegian).

Update! 16. September 2007: I've posted a follow up on this story here.

A friend of mine asked me to have a look at his Linux-server. "It behaves strangely" he said, most notably the web-server apache refused to start. It turned out to be more than just a problem with apache.

At work I need both Windows and Linux. So I've had a KVM switchbox from blackbox to easily switch between Windows and Linux. The KVM switch is showing it's age, since the display has lately become somewhat fuzzy. Recently I received two new LCD screens, and I decided to get rid of the old fuzzy KVM-switch. I wanted to try out Synergy - which enables two or more screens to be connected to different computers using one mouse and keyboard.

In a server rack, one console are usually shared by several different servers. One rack may contain servers belonging to different departments. One of those departments are usually doomed to have one trigger happy sysadmin. This sysadmin may reboot the wrong server accidentally using Ctrl+Alt+Del. Ever been exposed to one of those? Luckily, it easy to disable Ctrl+Alt+Del on Linux.

Recently, I bumped into a problem: I had received pictures from same event from three different sources (cameras). How could I sort these based on when the pictures were taken? A small Perl script are born to the rescue.