Tips for Testing the 2.5 Kernel (Linux Journal)

Okay, now that you actually have been convinced to try the 2.5 Linux kernel (see previous article), how can you test this kernel out. And, what should you do if you have any problems?

Well...yeah. I wish all of this information had been provided in the first place. If the first article was meant to convince me to test and then wait for a second article on the best specifics of how, I would have waited to do so.

If you are familiar with building 2.4 kernels, don't jump straight in to a 2.5. The What to expect from 2.5 document is still a must-read. It will save you a lot of pain.

But, having said that, I've already submitted one bug to the kernel bugzilla database (looks like an ACPI issue). One big no-no I've found: don't install the new modutils RPM on a Redhat 9 machine and then do the kernel upgrade available on upgrades.redhat.com. The 'new' 2.4 kernel won't boot, complaining that it needs an old modutils and that /bin/insmod.old doesn't exist (of course it doesn't - and that lies in /sbin anyway). I haven't tried it yet, but perhaps building the Redhat kernel*.src.rpm will fix that problem.

Other observations:

• 2.4 works well with USB and an IBM docking station for a Thinkpad laptop. 2.5 has more trouble with the passthrough. It needs quantification.
• ACPI is functional enough to work with most hardware devices, but not all, if enabled. The Thinkpad network card I have breaks if ACPI is enabled.
• Be careful about using LABEL boot statements. Best to have LILO or Grub boot with device names instead, in my experience. LABEL statements have alternatively worked and broken for me.

My layman's observation is that with Redhat 9, the 2.5 kernel mostly works, but most of Redhat's automatic module loading is broken. (E.g., if you have a network device 'bound' to eth0, you will probably need to manually load the module in rc.local at the end, rather than rely on the net scripts to load them for you. Anybody get this autoloading to work?) A different Toshiba laptop of mine also seems to run hotter than under 2.4.x, so be careful if you use this on heat sensitive laptops - ACPI power management is still in testing.

I'm curious what other people's experiences, if any, have been...

(of course one can't test HW support or speed with this but for testing generic features or patches (e.g. secure linux) this is great)

I've been testing 2.5 on an older P2 system. Mostly it runs smoothly. Only two issues found:

-The new GLIBC threading library (NPTL) as shipped in Redhat 9 breaks with the vanilla 2.5.67. This affects some programs, most notably rpm. The workaround is: run "export LD_ASSUME_KERNEL=2.2.5" before using rpm.

-The system tends to lock-up during X shutdown.

I am especially happy with the inclusion of the KAME IPSec suite.