Adventures with the Linux kernel

fox · June 11, 2018, 06:37:17 PM

I did something interesting today. In Linux Mint 18.3, I opened up the Software application and searched for linux kernels. To my surprise, the available kernels went up to 4.15. I say surprise because the updater was only offering 4.13. Linux Mint is great for stuff like this. You can try another kernel and if it doesn't work, boot back into the old kernel and get rid of the new. Which I had to do. I installed the generic kernel, the signed version of it and the corresponding linux-image. The result: it booted but wouldn't recognize the keyboard or mouse. So I looked again at what had been installed for the old kernel, and I was missing a file: linux-image-extra. It wasn't available for the 4.15 version I installed (4.15.0-23), but it was for an older version (4.15.0-15). When I installed that kernel (all four files), everything worked OK!

Now that I know this, I'm still going to uninstall the new kernel and wait for the Mint 19 upgrade in the event that the presence of 4.15.0-15 messes up the upgrade.

I wonder how else this knowledge can be used? Going back to openSUSE, Tumbleweed works on my 5k iMac because it used the 4.15 kernel, whereas the more stable LEAP won't boot because it uses the 4.14 kernel. But openSUSE has something called a build service, which allows you to take a default installer and change things in it. Makes me wonder how hard it would be to build an openSUSE LEAP installer with the 4.15 kernel? Not that I need it for anything, but might be fun to try it as an experiment.

Jason · June 12, 2018, 02:46:36 AM

Maybe the available kernels in the Update Manager was really itself updated? Because I just checked and I can get 4.15 release kernels there (latest is 4.0.15.0-23). But the tip about the package linux-image-extra is interesting. I wonder if that would have been included if it has been installed using UM?

fox · June 12, 2018, 04:02:51 AM

You're saying that the Update Manager offered you 4.15.0-23? Or you found it in the Mint 18.3 repos? In my case, the Update Manager never offered me anything beyond 4.13, at least until I installed 4.15.0-15 on my own. Now UM offers 4.15.0-23. I'm guessing that if I install it, it will install the extra and boot up my picky iMac.

Jason · June 12, 2018, 08:38:07 PM

Quote from: fox on June 12, 2018, 04:02:51 AM
You're saying that the Update Manager offered you 4.15.0-23?

Yes. When you click on the View -> Linux Kernels, 4.15 series kernels are in there. I'm still using the default 4.13 series though.

I did a kernel update recently and noticed that it did upgrade 4 packages one of which was linux-image-extra, so yeah, looks like it's included. But if you use a method outside of UM then you'll have to include it yourself.

fox · June 13, 2018, 06:59:04 AM

In my case, I wonder if 4.15 wasn't visible because I use the 4.8 kernel. The 4.13 kernel has been available for a long time in the Update Manager. I installed it several times, but removed it each time when I found that my 5k iMac wouldn't boot from it. Might be an interesting experiment to remove the 4.15 kernel, install 4.13, but boot to the usual 4.8 (an option in grub) and then see if 4.15 shows up. I can do these experiments with impunity because I have an extra Mint 18.3 partition on the spinning HD inside my iMac (as opposed to the SSD, also inside; both being part of the "Fusion Drive").

Update: 4.15 is indeed viewable; it just didn't come up automatically in the software updater like 4.13 did. I hadn't looked before under View -> Linux Kernels. Interestingly enough, once I installed 4.15.0-15 on that other partition, Update Manager showed me that the 4.15.0-23 update was available without having to go through the View -> Linux Kernels. So I installed it, and this time it brought with it the linux-image-extra module. Rebooting in that kernel worked fine.

Now that I know this, I'm debating whether to uninstall the 4.15 kernel altogether so that when Mint 19 is released, I can try upgrading in that extra partition to make sure it works before doing so in my main partition. I am potentially concerned that leaving the 4.15 kernel in 18.3 might cause the upgrade to behave differently than it would with the 4.8 kernel installed in my main partition. Do you think I have to worry about this, Jason?

Jason · June 13, 2018, 11:40:40 PM

Quote from: fox on June 13, 2018, 06:59:04 AM
Update: 4.15 is indeed viewable; it just didn't come up automatically in the software updater like 4.13 did. I hadn't looked before under View -> Linux Kernels. Interestingly enough, once I installed 4.15.0-15 on that other partition, Update Manager showed me that the 4.15.0-23 update was available without having to go through the View -> Linux Kernels.

Of course it would, it literally is an update to 4.15.0, that's why it has the -23 on the end. Remember that Linux Mint is a LTS distro (unless you use LMDE), so it doesn't actually upgrade things like kernels. It just updates the kernel version you have, that is, until you upgrade to a newer version of LM.

QuoteNow that I know this, I'm debating whether to uninstall the 4.15 kernel altogether so that when Mint 19 is released, I can try upgrading in that extra partition to make sure it works before doing so in my main partition. I am potentially concerned that leaving the 4.15 kernel in 18.3 might cause the upgrade to behave differently than it would with the 4.8 kernel installed in my main partition. Do you think I have to worry about this, Jason?

I doubt you will have to worry about but you can certainly revert if you wish. I would imagine that the LM upgrade can handle this. It should just notice that you already have newer a kernel and just leave it alone. You can always do a Timeshift backup before you do the upgrade so if anything goes wrong, you can revert back to before the upgrade.

However, I find it puzzling that you have 4.8 series kernel because I installed Linux Mint 18.3 freshly to get the KDE version a month ago, I guess now, and I don't recall ever upgrading to a new series. so I think it came with the 4.13 series. Perhaps that is just with the KDE version though. Really not sure. And it's possible I installed a newer kernel series with Update Manager -> View -> Kernels and just forgot :-)

fox · June 14, 2018, 07:24:27 AM

Quote from: Jason Wallwork on June 13, 2018, 11:40:40 PM
....

However, I find it puzzling that you have 4.8 series kernel because I installed Linux Mint 18.3 freshly to get the KDE version a month ago, I guess now, and I don't recall ever upgrading to a new series. so I think it came with the 4.13 series. Perhaps that is just with the KDE version though. Really not sure. And it's possible I installed a newer kernel series with Update Manager -> View -> Kernels and just forgot :-)

The reason I have the 4.8 kernel is that the version of Mint I originally installed was 18.2, not 18.3. When I upgraded, I was offered a newer kernel (4.13 I think) in the software updates. Tried it, doesn't boot on my 5k iMac, so I uninstalled it. I continue to get offers to upgrade that kernel every time an update is released - I just don't install it.

Jason · June 14, 2018, 03:51:34 PM

Ohhhh. That makes sense.

Btw, I did put Linux Mint 19 Cinnamon beta on my laptop and did the steps to install KDE on it. It works to login but I haven't had to time to do more with it to make sure it actually works decently. I'll start a new topic and report back whether it works or not.