Speed up dracut building CentOS 6.5 initrd in qemu64

paulfurtado · 12-16-2014, 08:46 PM

We use qemu 64 bit virtualization without KVM to generate CentOS 6.5 images with kickstart. This works great, but it spends upwards of an hour building the initrd with dracut which is by far the biggest bottleneck. I've tested that the bottleneck does not occur when using KVM, however on our production build system KVM is unavailable and it would be great to make this work without KVM.

I'm curious what tricks/hacks there are for speeding up this process.

Are there significant unnecessary steps in dracut which can be disabled?
Can we disable dracut and use mkinitcpio? (would mkinitcpio even be faster?)
Can we pre-build the initramfs and skip dracut?
Maybe the way that qemu is emulating some device is what's slowing it down?
Other suggestions?

jefro · 12-17-2014, 08:24 PM

There is little one can do if they don't enable the host's ability to interact with the vm. I assume this is what you mean.

You may be able to simply make these images on a system that you can add in hardware support.

I'd assume the bottleneck is the processor on host emulating the virtual computer. If ram or hard drive space or even cpu allocation then you might just make changes to base client.

The last thing might be to pre-allocate the virtual hard drive.