Bootstrapping Fedora 12 …. A simple review……

February 12, 2010

A GNU/Linux system , in general , has three phases of booting: kernel and initrd load , system and then services initialisation.In the first phase , the bootloader (GRUB ) loads the kerneland the initial RAM drive (initrd) into the memory. In the second phase , the essential initialisation task , like a file system check , UDEV device node generation , filesystem  mounts , network initialisation , setting the hostname , date and time and other basic stuff are done. And in the third  phase, as the system enters a run level, daemons and services like cups, httpd and the like are started.

Dracut – The current incarnation of mkinitrd sucks for a variety of reasons. Fedora developers took up the charge of creating “initramfs infrastructure” that has “…as little as possible hard coded into the initramfs”. And it looks like they made it big. The Dracut architecture is event-driven and make use of a Bash shell , eliminating Nash from initrd’s picture. This has a three fold advantage over using a minimal shell or a home grown replacement.  The end result is that Nash isn’t really required any more , and it will be dropped in a future release. However , in Fedora 12 , Nash is still used in a few places including Anaconda , the system installer.

KMS and Plymouth – In simple terms , in KMS (Kernel Modesetting ) , setting the screen resolution and colour depth as well as the video memory is managed by the kernel itselft.The advantage?Here’s an easy one : the transition from the splash screen to the display manager becomes flicker free.Since the kernel itselft manages the video memory instead of the X11 video driver , in case a Kernel Oops or panic occurs , the kernel can wipe out the X11 display and then show an error message. Compare this with the pre-KMS era where it would simply freeze up the system requiring a manual reset. Plymouth has already tasted mainstream success , being included with the current Mandriva release. It is slated to replace Ubuntu’s USplash , and with all the inherent problems of Bootsplash and the fact that Plymouth can work with UMS and KMS , we should be able to see most , if not all distro switch to Plymouth to provide a graphical boot.

Well , the infrastructure is now in place. All it needs is a bit of tweaking to get it to where the system boots in less than 15 seconds . There’s this unresolved bug , which causes Plymouth to be the first job to get killed when the system is shutting down , creating a blank screen(but it’s still flicker free) and dampening the shutdown experience. This thing will be corrected once UED’s make an appearance in Fedora.That’s the only way to fix it without using what we call ugly hacks.


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