[Yum] Weird yum/kernel problem

Anders Blomdell anders.blomdell at control.lth.se
Fri Dec 12 14:58:33 UTC 2014

Hash: SHA1

On 2014-12-12 05:03, Bob McKay wrote:
> I’m not sure whether the problem I’m about to describe is a yum
> problem, or a problem with the way the kernel packages are set up in
> our Fedora 20 server. If this is the wrong place to ask, I’d really
> appreciate a pointer to the right one (the Fedora mechanism for yum
> kernel updates seems to be particularly complex, and I haven’t
> properly understood it yet, which is why I’m not sure where the real
> problem lies).
> I have some RAID hardware that requires a driver module to be built
> after every kernel update (all updates are performed with yum, not
> package-manager). My process is to disable the hardware, boot to the
> newly-updated kernel, build and install the module, then re-enable
> the harware and reboot. Since about mid year, I have been having
> repeated problems building the module. When I build it, the build
> appears to succeed, but install fails, saying that the module wasn’t
> built against the running kernel. This seems to be correct - when I
> manually check the magic of the built module, it shows the preceding
> kernel (i.e. at the moment, 3.17.2), although it  was built under a
> running 3.17.3 kernel, and is installed in the correct location for
> 3.17.3 modules.
> By the way, I have no clear idea how I got to a working 3.17.2 kernel
> - the problem originally occurred at 3.16.3, and I was stuck in that
> kernel for a long while. Fortunately I had some free time on the
> server a few weeks ago. Somehow something in a complex sequence of
> grub2-install, grub2-mkconfig , removals and reinstallations of the
> corresponding kernel and kernel-devel, and module rebuilds changed
> something, and I managed to get the 3.17.2 update working. But I
> haven’t been able to figure out what it was, or to reproduce it
> since.
> Why it looks like it should build correctly: at the time of building,
> all kernel components have been fully updated. For example, at the
> moment, I have kernel, kernel-devel, kernel-modules-extra and kernel
> devel all at 3.17.3 (but of course, I also have earlier versions of
> kernel, kernel-headers and kernel-modules-extra installed as well -
> in this case, including 3.17.2). When I try to do the build and
> install, it is booted in 3.17.3. So I don’t understand why it builds
> a 3.17.2 module.
> It seems that at the time it is building the module, the system is
> somehow defaulting to building for 3.17.2. That suggests that a
> necessary flag recording the current kernel version isn’t being
> updated when the kernel is updated or booted - I haven’t been able to
> figure out how the system decides what the current kernel is, so I
> don’t know where this flag might be. Any suggestions on how this is
> done (and why it might be failing, or how to check it) would be
> really appreciated.
> There is more detail on the problem at: 
> http://forums.fedoraforum.org/showthread.php?t=300863 
> https://bugzilla.redhat.com/show_bug.cgi?id=1167222 but unfortunately
> no responses in either place yet (possibly because there isn’t
> sufficient detail - but I have no idea what else to supply).
> The system is a production server; it’s currently running stably with
> 3.17.2, and I can’t reboot very often, so any suggestions that would
> help me to diagnose this problem without rebooting would be
> particularly appreciated.
Use appropriate scripts in /etc/kernel/postinst.d or /etc/kernel/postinst.d/dkms
and kernel modules can be rebuilt right after a new kernel is installed
(of course you need kernel-devel).


- -- 
Anders Blomdell                  Email: anders.blomdell at control.lth.se
Department of Automatic Control
Lund University                  Phone:    +46 46 222 4625
P.O. Box 118                     Fax:      +46 46 138118
SE-221 00 Lund, Sweden

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