Failing to downgrade Kernel.

[Gat Pelsinger]

I am on Arch and for experimental purposes I need to downgrade my Kernel to 4.20.

 

First I tried letting pacman do it by providing the URL to the package from the ALA (Arch Linux Archives). The installation completed but I got an error from mkinitcpio, the program that makes the compressed initramfs image, that no modules were found in /lib/modules for the Kernel I was downgrading to. I took a look and no folder was for the Kernel, and that was to be expected. I still tried to boot the older Kernel but the system froze on me. If I disable quite mode and optionally enable Kernel Debug level logging (level 7), I see that I get a Kernel panic and it throws an error that it is unable to mount the root filesystem on an unknown block. I had this issue prior as well and fixing my initramfs which wasn't configured correctly fixed the problem. I also successfully managed to bork my system because my dumb brain forgot to make a backup of my current initramfs, and not just the current Kernel, but fixing it wasn't a big problem.

 

But the thing is, where do I configure my modules? I first tried installing the linux-headers package (of the 4.20 Kernel), but I was told that I have to compile them. But when I try to compile it using "sudo make -j8" or even just "sudo make" (sudo is required), I get an error that a Makefile is not present in a directory that is also not present. I don't think the error is important, I am probably just doing it wrong (lol forgive me. I borked my system again and so I can't check right now -_-). I still tried to install the Kernel with the linux-headers package installed (of that version) but not compiled, and nothing changed.

 

Am I supposed to compile my own modules or what? Is the older Kernel even compatible with the newest packages and the environment? Do I have to install an older version of Arch itself?

[Alex Atkin UK]

9 minutes ago, Gat Pelsinger said:

I am on Arch and for experimental purposes I need to downgrade my Kernel to 4.20.

 

First I tried letting pacman do it by providing the URL to the package from the ALA (Arch Linux Archives). The installation completed but I got an error from mkinitcpio, the program that makes the compressed initramfs image, that no modules were found in /lib/modules for the Kernel I was downgrading to. I took a look and no folder was for the Kernel, and that was to be expected. I still tried to boot the older Kernel but the system froze on me. If I disable quite mode and optionally enable Kernel Debug level logging (level 7), I see that I get a Kernel panic and it throws an error that it is unable to mount the root filesystem on an unknown block. I had this issue prior as well and fixing my initramfs which wasn't configured correctly fixed the problem. I also successfully managed to bork my system because my dumb brain forgot to make a backup of my current initramfs, and not just the current Kernel, but fixing it wasn't a big problem.

 

But the thing is, where do I configure my modules? I first tried installing the linux-headers package (of the 4.20 Kernel), but I was told that I have to compile them. But when I try to compile it using "sudo make -j8" or even just "sudo make" (sudo is required), I get an error that a Makefile is not present in a directory that is also not present. I don't think the error is important, I am probably just doing it wrong (lol forgive me. I borked my system again and so I can't check right now -_-). I still tried to install the Kernel with the linux-headers package installed (of that version) but not compiled, and nothing changed.

 

Am I supposed to compile my own modules or what? Is the older Kernel even compatible with the newest packages and the environment? Do I have to install an older version of Arch itself?

I'm not familiar with Arch or compiled a kernel in years, but  I'd think you'd have to compile the whole kernel and that entails also telling it which modules you want.

 

Compiling a newer kernel you can usually import the old configuration from your distros kernel source, but IMO theres pretty much zero chance you'll be able import a newer config into an older kernel.

 

If for some bizarre reason you need an older kernel, I'd definitely install a version of Arch that used that kernel.  But what sort of experiment you are doing that needs this ancient kernel I do not know.

[Gat Pelsinger]

@Alex Atkin UK

 

I don't see why I need to compile the Kernel again when I have the actual binary. Not that I need to do any changes to the Kernel.

 

24 minutes ago, Alex Atkin UK said:

I'd definitely install a version of Arch that used that kernel

Yeah I probably thought of that. Even if I managed to run an older Kernel, will it even run with modern Arch and its packages?

[igormp]

First of all, live boot into an arch install, chroot your system and then just use pacman to reinstall the kernel and whatnot to restore your system. Been there, done that, at least that's an easy fix.

 

Now for your actual issue, why the hell do you need such an old kernel? Anyway, you're better off building your own kernel:

https://wiki.archlinux.org/title/Kernel/Traditional_compilation

 

1 minute ago, Gat Pelsinger said:

I don't see why I need to compile the Kernel again when I have the actual binary. Not that I need to do any changes to the Kernel.

 

Your binary might not be compatible ABI-wise with your current install.

[Kilrah]

43 minutes ago, Gat Pelsinger said:

First I tried letting pacman do it by providing the URL to the package from the ALA (Arch Linux Archives).

If you don't want to compile the whole kernel and modules yourself you likely need to install the matching modules package.

[Gat Pelsinger]

13 minutes ago, Kilrah said:

If you don't want to compile the whole kernel and modules yourself you likely need to install the matching modules package.

I have no idea where I would find that. I thought linux-headers is all I needed, but it won't compile.

[Gat Pelsinger]

@igormp

 

16 minutes ago, igormp said:

First of all, live boot into an arch install, chroot your system and then just use pacman to reinstall the kernel and whatnot to restore your system.

Yes I said that I fixed my system before breaking it once again. I know this.

 

Second, I have compiled a Linux Kernel several times and this probably would work as the compilation itself generates those modules. But in my opinion, there should be zero reason for me to compile my Kernel if the binaries are already present. Just don't know where I get the modules from.

 

Also I am not THAT curious for my experimental purpose that I would spend 3-4 hours literally torturing my poor laptop processor so I would have to give a pass unless I really have to try the older Kernel.

[Kilrah]

Where did you get the precompiled kernel from? Same place should have modules.

 

And yes it's entirely possible a bunch of other things break if you downgrade just those.

[igormp]

14 minutes ago, Gat Pelsinger said:

Just don't know where I get the modules from.

They come from the kernel repo itself, hence why you need to build them, as you should know since you've done it before.

[Nayr438]

1 hour ago, Gat Pelsinger said:

I took a look and no folder was for the Kernel, and that was to be expected.

Then something went wrong installing the package.

Spoiler

 

1 hour ago, Gat Pelsinger said:

 Is the older Kernel even compatible with the newest packages and the environment?

Probably not. Various packages are built around the current kernel api/abi and filesystems are really not backwards compatible with older kernels.
There is also a chance how the initial ramdisk is made has changed since it ships its own mkinitcpio preset, meanwhile newer kernels don't.

 

1 hour ago, Gat Pelsinger said:

Do I have to install an older version of Arch itself?

This really isn't a option unless you want to manually grab every package version matched from the archive, a base install is around 200 packages.
 

[Gat Pelsinger]

@Nayr438

30 minutes ago, Nayr438 said:

Then something went wrong installing the package.

I just did "sudo pacman -U https://asia.archive.pkgbuild.com/packages/l/linux/linux-4.20.10.arch1-1-x86_64.pkg.tar.xz". I am using the Asian mirror. So I just grabbed a standalone package, and nothing else.

 

31 minutes ago, Nayr438 said:

This really isn't a option unless you want to manually grab every package version matched from the archive, a base install is around 200 packages.

Wait so you are saying using an older Kernel or older version of Arch or any other distro is just not possible? Even after compiling the Kernel yourself?

[Nayr438]

1 hour ago, Gat Pelsinger said:

Wait so you are saying using an older Kernel or older version of Arch or any other distro is just not possible? Even after compiling the Kernel yourself?

The kernel itself is likely to be problematic on Arch current if it works at all.

If anything you might be able to pull the current PKGBUILD and reversion it, but I would still expect problems.

In terms of running an old version of Arch, the problem is Arch itself isn't versioned, there is no set release. If you wanted to run an old version of Arch you would need to grab an old archiso and manually pull in packages based on versioning.

 

As far as other distros, I know ubuntu keeps a archive of old releases and archives packages similar to Arch. If I recall you can even replace the mirrorlist urls with the the archive mirrors to use apt as you would normally, they would just be out of date packages based around that release.

https://old-releases.ubuntu.com/releases/
https://askubuntu.com/questions/91815/how-to-install-software-or-upgrade-from-an-old-unsupported-release/91821#91821
 

[Gat Pelsinger]

@Nayr438

 

Freak Ubuntu, CAN I DO THIS DEBIAN?

[xAcid9]

I got few errors when installing but it runs. 

 

[Gat Pelsinger]

@xAcid9

 

HOW?

 

I see you are using Manjaro rather than Arch, but idk if that makes much difference.

 

Just please elaborate your steps. Where did you download the Kernel, and what else you downloaded with it if any, and what did mkinitcpio say, I mean were the modules present in /lib/modules? 

[xAcid9]

4 hours ago, Gat Pelsinger said:

@xAcid9

 

HOW?

 

I see you are using Manjaro rather than Arch, but idk if that makes much difference.

 

Just please elaborate your steps. Where did you download the Kernel, and what else you downloaded with it if any, and what did mkinitcpio say, I mean were the modules present in /lib/modules? 

I just installed both the kernel and the kernel header from the link you provided with pacman -U 
Yeah there's some missing modules errors, libcrypt something. I don't  remember mkinitcpio output.

Kernels: https://asia.archive.pkgbuild.com/packages/l/linux/
Headers: https://asia.archive.pkgbuild.com/packages/l/linux-headers/

 

[Nayr438]

12 hours ago, Gat Pelsinger said:

Freak Ubuntu, CAN I DO THIS DEBIAN?

Old Ubuntu actually wasn't that bad. I'm not familiar enough with Debian to know.

 

4 hours ago, Gat Pelsinger said:

I mean were the modules present in /lib/modules? 

They are part of the "linux" package, if "/usr/lib/modules/4.20.10-arch1-1-ARCH/" doesn't exist then it didn't install correctly. Try reinstalling it, or manually extracting it and re-running "mkinitcpio -p linux".

[Sauron]

20 hours ago, Gat Pelsinger said:

I have no idea where I would find that. I thought linux-headers is all I needed, but it won't compile.

Likely because it expects your system to have old packages. This, by the way, is the reason Arch Linux officially discourages partial upgrades or downgrades.

 

What are you even trying to do that requires an old unsupported kernel? Will 4.19 LTS do? https://aur.archlinux.org/packages/linux-lts419 https://aur.archlinux.org/packages/linux-lts419-headers

 

If you MUST have 4.20 I would recommend taking the 4.19 PKGBUILD from the aur package and changing it to pull 4.20 instead, the required steps are likely the same.

4 hours ago, xAcid9 said:

I just installed both the kernel and the kernel header from the link you provided with pacman -U 
Yeah there's some missing modules errors, libcrypt something. I don't  remember mkinitcpio output.

Kernels: https://asia.archive.pkgbuild.com/packages/l/linux/
Headers: https://asia.archive.pkgbuild.com/packages/l/linux-headers/

 

It's worth noting that your system may have packages installed that OP's does not. Also you may have different versions of various packages.

[goatedpenguin]

Doing this will result in no good. Packages, libs, dependencies depend on some stuff from the newer kernel that the older kernel does not have. You should always do this stuff on a vm and not your physical installation…l