[elrepo] Downgrading between kernel versions that use kmod-megaraid_sas

[Phil Perry]

On 26/02/2021 19:50, Roger Sewell wrote:
> 
> Having successfully got a test kernel to run using kmod-megaraid_sas,
> I'm now having difficulty working out how to downgrade to my previous
> kernel needing the same driver.
> 
> (I do have a backup disc image, so I'm not up a creek without a paddle,
> but I want to understand how to do it properly and whether or not I'm
> experiencing a bug.)
> 
> I originally had running
> 
> kernel-4.18.0-193.6.3.el8_2.x86_64 and
> kmod-megaraid_sas-07.710.50.00-1.el8_2.elrepo.x86_64 .
> 
> I was sent
> 
> kernel-4.18.0-287.el8.test.x86_64
> 
> and its associated devel etc packages. I compiled kmod-megaraid_sas from
> its 8.3 src package for this new kernel giving
> 
> kmod-megaraid_sas-07.714.04.00-1r.el8_3.test.x86_64.rpm
> 
> which installed successfully. Apart from unrelated issues this new
> kernel ran OK. However, with this setup, the original kernel wouldn't
> run any more, instead it hung after the first occurrence of "Reached
> target Basic System" in boot.log .
> 
> Now I want to downgrade to the original kernel and kmod-megaraid_sas
> package. My first instinct was to simply do
> 
> yum --cacheonly downgrade kmod-megaraid_sas-07.710.50.00-1.el8_2.elrepo.x86_64.rpm
> 
> (providing that package in the current directory) thinking that this
> would result in the 8_2 package in place (it did) and the 8_2 kernel now
> working (with the test kernel now not working).
> 
> However, instead, both kernels hang at the first occurrence of "Reached
> target Basic System", before finding the root device.
> 
> Moreover, the 8_2 kernel's initramfs file did not get its last
> modification time updated during the downgrade, although when installing
> kmod-megaraid_sas to start with, the initramfs file appeared to get
> longer and have its modification time updated.
> 
> Questions:
> 
> a) Should what I did have worked ?
> b) Is there a bug in the kmod-megaraid_sas package suggested ?
> c) What alternative procedure should I have used ?
> d) Do you need any additional info to work out what's going on ?
> 
> With thanks in advance,
> Roger Sewell.

Hi Roger,

In principle, what you did should have worked.

As it looks like your initramfs didn't update, I would try forcing a 
manual update with 'dracut -f ...' to see if that fixes things.

Phil