I decided to switch all my machines to kernel 2.6. I now consider the kernel 2.6 stable enough, at least for the use of my machines. Except for my workstation on which I like to add some patches, I am using Debian kernels for my other machines. Moreover some of them are very slow (a parisc@60 MHz and a sparc@110 MHz), and building a kernel on such machines takes very long time.
I started with my a backup server, it was very easy,
Then I switched my firewall. It was not so easy as for my backup server,
as I only have a 256 MB disk (actually a compact flash card). Because of
its size, it was not possible to have two kernels at the same time on
the disk. I decided to remove the old 2.4 kernel (/boot and
/lib/modules), to install the new 2.6 kernel. Then I typed
started to pray. As I don't have neither a display nor a keyboard on
that machine, I started to look both at the hard disk's LED and at a
console on my workstation on which I started
ping fourier. After a
some time (I don't know exactly how much, in such situations seconds are
like minutes), there was some echo reply. Wonderful!
After such successes, I decided to continue and to switch my hppa machine. Again apt-get, then a quick look at the palo's documentation to know how to specify an initrd image, and then reboot. After a lot of time, it was still not possible to ping the machine. Shit! PALO has the possibilty to specify an alternate kernel in case of a problem, however in that case it seems it has failed... or the boot was mabe successfull. Half an hour later, after I plugged a screen, a keyboard and a null-modem serial cable, I understood the problem: the module for the network card was not loaded (whereas it was directly binded into the 2.4 kernel). And hotplug doesn't load it as it is not on a PCI bus. I tooked my keyboard and started to write my login. Nothing. The keyboard's module was also not loaded. I switched back to the 2.4 kernel, I put a lot of modules into /etc/modules (network card, keyboard, mouse, sound card, parallel port, serial port, etc.). And it worked!
Moral: Don't change your kernel when you only have very few time to do that. It always take a lot longer than expected.