What is warm rebooting?
Recent Linux kernels support a new feature called kexec. Basically it allows you to load a new kernel image into memory, and then boot into that kernel directory without having to do a full reboot of the machine. This can speed up reboots significantly.
Where do I get it?
Download it here:
You'll also need Python version 2.4 installed, as well as the kexec-tools package.
How do I install it?
If you downloaded the .deb version, then running
dpkg -i kexec-chooser_0.1_all.deb should work.
If you downloaded the .tar.gz version, then your best bet is to copy kexec-chooser into /usr/sbin. This package is really designed to work on Debian, so your milage may vary on other distributions.
How do I use it?
will print a list of available kernels.
will indicate that you want to warm-reboot into the 2.6.17 kernel. Note that this won't actually reboot your machine. When you reboot via the reboot command, or GNOME's Shut Down/Reboot dialog, then kexec-chooser will warm-reboot into the kernel you specified.
See the man page for more information.