Linux live core changes

written by Tomas M. 276 days ago

The last version of Linux Live scripts dates back to the year 2009. A lot of time passed since then and the core concepts should be reconsidered.

Current approach is following:
- maintain a fixed size initrd image
- use busybox for everything
- use huge kernel (in order to support as much hardware out of the box as possible without loading modules)
- when done with booting, keep initrd in memory

The current approach has several disadvantages.

First of all, the fixed-size initrd is a filesystem (currently ext2) which needs to be decompressed and loop-mounted in memory. As long as the initrd stays available (which is forever in Slax), it consumes the same amount of memory all the time (currently 4MB). For that reason, there is a pressure to make the initrd small, which contradicts the need to include lots of useful stuff there (eg. network card drivers).

Being an ext2 filesystem in general, it is more complicated to create and maintain. If initrd is replaced by initramfs, it wouldn't be even necessary to include ext2 directly in kernel, and furthermore it would be much easier to cleanup the parts of it from memory which are no longer needed (eg. drivers). One can simply 'rm' the stuff and memory can be reused.

The 'huge' kernel (as Slackware calls it) is great for general purpose booting, but it boots much slower than the base kernel without all unnecessary drivers.

Busybox is also great for embeded systems, but it usually cares about memory usage and binary size, which is not our point of interest any longer. The most important factor today is SPEED, and FEATURES. Several parts of linux live scripts are coded especially for busybox's ash usage, it makes the coding more complicated. I would prefer to use bash instead of busybox's ash. And if bash is added (including its dependencies), there is nothing easier to even add the other linux utilities like mkdir, touch, and so on.

While thinking about it, it may be even more interesting to include full core of the operating system in initramfs, maybe even including udev and linux drivers. This needs further investigation.

So the key modifications which I would like to happen could be sumarized as:
- replace initrd by initramfs
- include more stuff in initramfs, and delete it when it's no longer needed
- possibly include full-featured bash
- use smaller kernel for faster booting
- investigate the possibility to use minimal Slackware install even in initramfs, take into consideration how to attach the other filesystem parts (how to setup aufs union and add squashfs modules)