The idea is based on a posting I recently found on fedora-devel-list: http://www.redhat.com/archives/fedora-devel-list/2004-July/msg01399.html
I recently installed Fedora Core 3, and I thought I should give this trick a whirl as it looks promising and is easy to implement. And it should also work with other Linux distributions with a modified script.
Before trying this out, however, it is always a good idea to disable any unused services from your installation. It also saves a few seconds and helps performance in general to disable the "Red Hat Graphical Boot", SELinux and exec-shield (but do not disable SELinux and exec-shield if you are running a multiuser system or a server). Also, I have 256 megs of RAM on this laptop, and I have never found the "readahead" thingy to have any benefits on my boot time.
You will first need to disable prefdm from /etc/inittab and place the modified prefdm from the zip file in /etc/init.d/. You will then need to activate this new prefdm service within SysVinit by creating the appropriate links as follows:
cd /etc/rc.d/rc5.d ln -s S26prefdm ../init.d/prefdm cd ../rc6.d ln -s K01prefdm ../init.d/prefdmMoreover, X.org needs xfs, and possibly netfs if your home is located on the network, so you will need to have them started earlier than usual:
cd /etc/rc.d/rc5.d mv S90xfs S25xfs mv S75netfs S25netfsIn prefdm you will find a "sleep" command. It is used to let gdm/kdm/xdm start quickly and completely before loading the rest of the services in the background. I used 10 seconds, but you can try more or less, depending on your needs and your computer.
With this setup, I am down to ~45 seconds to the gdm login prompt, and to between ~1:15 and ~1:25 minutes, depending on the services loading in the background, to a fully loaded GNOME 2.8 desktop. In comparison, Windows XP takes respectively ~40 seconds and ~1:05 minutes. Not too shabby!
Also for laptops, check out Software Suspend 2. On this laptop, version 2.1.5 suspends to disk in 15 seconds, and resumes in 20 seconds! Moreover nothing is broken after a resume! I am truly amazed. You will however need to use a vanilla 2.6.9 kernel as the kernel panics with the Red Hat patches.