Simplicity is a form of art...

The Linux ".d" approach

Many services on a Linux system use a *.d directory approach to make their configuration easily configurable by other services. This is a remarkably simple yet efficient method for exposing services towards other applications. Let's look into how this .d approach works.

Take a look at the /etc/pam.d …

Qemu-KVM monitor tips and tricks

When running KVM guests, the Qemu/KVM monitor is a nice interface to interact with the VM and do specific maintenance tasks on. If you run the KVM guests with VNC, then you can get to this monitor through Ctrl-Alt-2 (and Ctrl-Alt-1 to get back to the VM display). I …

photorec to the rescue

Once again PhotoRec has been able to save files from a corrupt FAT USB drive. The application scans the partition, looking for known files (based on the file magic) and then restores those files. The files are not named as they were though, so there is still some manual work …

Comparing performance with sysbench: performance analysis

So in the past few posts I discussed how sysbench can be used to simulate some workloads, specific to a particular set of tasks. I used the benchmark application to look at the differences between the guest and host on my main laptop, and saw a major performance regression with …

Comparing performance with sysbench: memory, threads and mutexes

In the previous post, I gave some feedback on the cpu and fileio workload tests that sysbench can handle. Next on the agenda are the memory, threads and mutex workloads.

When using the memory workload, sysbench will allocate a buffer (provided through the --memory-block-size parameter, defaults to 1kbyte) and each …

Comparing performance with sysbench: cpu and fileio

Being busy with virtualization and additional security measures, I frequently come in contact with people asking me what the performance impact is. Now, you won't find the performance impact of SELinux here as I have no guests nor hosts that run without SELinux. But I did want to find out …

Why would paid-for support be better?

Last Saturday evening, I sent an e-mail to a low-volume mailinglist regarding IMA problems that I'm facing. I wasn't expecting an answer very fast of course, being holidays, weekend and a low-volume mailinglist. But hey - it is the free software world, so I should expect some slack on this, right …

nginx as reverse SMTP proxy

I've noticed that not that many resources are online telling you how you can use nginx as a reverse SMTP proxy. Using a reverse SMTP proxy makes sense even if you have just one mail server back-end, either because you can easily switch towards another one, or because you want …

devops - how hard can it/it can be

Dieter made a good reference to devops and the open source community and (correctly) points out that, even in a more collaborative scene such as the free software communities', there is still distinction between development and operations. And it isn't hard to see commonalities between enterprise organizations and free software …

qemu monitor cd change

I've been playing around with kvm (which uses qemu) to try out other operating systems and Linux distributions. Up until now, little progress on that part (not because it is difficult, just little time) but there are a few things worth mentioning. For this post, let's start with a quicky …