Meet with buildroot - Custom Linux

I was thinking about having a really small linux system for cloud images. I already knew about the concept of JeOS (Just enough OS), but I still can't agree having more than 100MB as a disk. Actually, I would like to be able to have something around 50 MB. I knew about CirrOS, which we use for functional testing OpenStack. CirrOS is small, the qcow image is 10 Megs. So I looked at the launchpad site, and discovered, that cirros is using buildroot to create the root filesystem. That was enough inspiration for me to try to create a very minimal Linux. First build

$ mkdir myl
$ cd myl
$ wget -qO - http://buildroot.uclibc.org/downloads/buildroot-2013.02.tar.gz | tar -xzf -
$ cd buildroot*
$ make qemu_x86_defconfig
$ time make

Before starting make, I looked into the configuration, and it turned out, that qemu_x86_defconfig includes building a kernel, so I expect the build to last at least for an hour. In the meanwhile, it makes sense to read how I will start the machine:

$ cat board/qemu/x86/readme.txt

In the end, it was quicker than I expected:

real 26m5.626s
user 32m15.753s
sys  3m55.447s

And, let's see how it boots!

qemu-system-i386 -M pc \
-kernel output/images/bzImage \
-drive file=output/images/rootfs.ext2,if=ide \
-append root=/dev/sda

Wow! that was fast. To get a feeling on how fast it is, see this video And you might be interested in the size of the whole stuff:

$ du -shc output/images/

3.2M output/images/
3.2M total