mirror.dongdigua.github.io/org/fix_tty.org

[Custom Kernel] Fix TTY after Fedora 37 Upgrade

• What Happened
• Ask for help
• Thought

What Happened

After switching to f37, something changed:

• sddm don't work
• sway don't have environment variables
• v2rayA don't start automatically

but those are not vital. One day I wanted to login to tty, it just stuck. However, default kernel works. I wonder how~ I wonder why~

But before this, I noticed some other scenario:

• old f36 kernel and kernel built on f36 won't boot
• newly built kernel don't have startup screen with fedora logo
• when I added a new kernel, the grub select the f37 kernel by default

I didn't take them seriously, until my kernel goes wrong as above.

How to fix that? is there any suspicious config I added? So I rolled back to an older version of my config but still don't work.

Ask for help

I think I can't solve this, therefore, I asked for help at #kernel on libera.chat (weechat is really great… to have English-only chat)

chat log

<digua> hello, I made a custom kernel, but I cannot switch tty
<tdr> thats not usually a kernel problem.
<digua> but if I switch to fedora default kernel, it work
<tdr> did you include everything your init system uses/needs?
<tdr> its your init that needs to spawn the other tty getty's / logins
<tdr> so systemd or whatever init system youre using
<digua> what getty need to include?
<tdr> ok i guess i said im wrong there, it can be either
<jn> if you use the same userspace with both kernels, the next thing to check is the configs
<jn> /boot/config-* or /proc/config.gz
<jn> maybe there are differences there that explain the different outcomes
<tdr> there is a diff tool in the scripts directory too, much better than normal diff
<tdr> diffconfig
<tdr> digua, which distoro kernel did you replace?
<digua> fedora to xanmod
<tdr> i think some need stuff in the initramfs to get the muti tty stuff too
<digua> o I noticed one thinig in dmesg
<tdr> digua, doesnt fedora use plymoutth or smoeting in the ramdisk normally .. you may want to pull apart your old initramfs and look in there too
<digua> when I switch tty, dmesg says something about rfkill
<tdr> rfkill is radio on/off
<tdr> so wifi or bt or whatever
<digua> tdr, plymouth is the fedora logo support? i don't have that in my kernel
<digua> does it have an impact on tty?
<tdr> depeneds what <they> do with or around it
<tdr> there's no solid rules of what is done where or how, as long as requirements are met for <next step>

<digua> tdr, so I checked both initramfs, and I only found intel microcode, so now the problem isn't at initramds
<tdr> you didnt unpack it the right way
<tdr> if dracut made it, there are 2 parts
<digua> i use cpio -idv < file
<tdr> digua, https://www.thegeekdiary.com/centos-rhel-7-how-to-extract-initramfs-image-and-editview-it ... the skipcpio method
<tdr> digua,  /usr/lib/dracut/skipcpio  <your initramfs file> | zcat | cpio -ivd
<tdr> lsinitrd also works to see whats there without doing much else
<digua> thanks, I thought it can't contain only microcode :)
<tdr> it can be a chamber of "secrets" easy enough
<small> jn: hmm

<digua> I'm back! after a noon of compiling with ealier config
<digua> but tty STILL don't work, I think the f37 upgrade breaks it
<digua> tdr, so I think it's not my config issue :-|
<tdr> hrm i'd be cautious saying a distro released/tested kernel breaks your boot.  not saying its impossible, but i'd also try their stock config.
<tdr> specifically, their kernel and initramfs pair together.  before opening a bug with them
<digua> I remembered, when I upgraded to f37, the f36 kernel and kernel build on f36 all don't boot, so maybe I need to config based on the f37 default?
<digua> building with f37 config works fine, and I will reconfigure based on it :)
<digua> tdr, thank you for your generous help

Yeah, there is something that changed after f37 upgrade and I'm still using the config I modified based on f36 one!

So I grabbed the f37 config at /boot and replaced .config, then, without any modification, compile it.

It fucking worked!!! also the startup logo (plymouth)

For I have recorded what I change I have made based on the default kernel, it's not too difficult to reconfigure it. The next step is to find out what is really going wrong…

Thought

The book Absolute OpenBSD says people should not build a custom OpenBSD kernel, that's right for OpenBSD. Because it's application and kernel are together, and it have the magical config(8) to modify the kernel biniary.

For Linux user, it's still good to have a configured kernel.