On Wednesday, 31 July 2019 23:31:20 BST Jack wrote:
> I just built a new PC, and I'm having a problem getting it to boot with
> a custom configured kernel (gentoo-sources-5.2.4.)  If I start with a
> blank config and work through "make xconfig" the resulting kernel and
> initramfs (genkernel) doesn't boot (just hangs after loading
> initramfs.)  

Does it spit out any errors on the console?


> So, starting with the config from the running kernel from
> the live install medium, running make oldconfig then genkernel, it
> boots fine.  I assume my problem is removing something important while
> trying to remove all the unnecessary options for supporting hardware
> I'll never use.
> 
> However, if I start with the .config which workd, and "make xconfig"
> and select "Supported processor types" under "Processor type and
> features" and then unselect "Support Intel Pprocessors" (I have a
> Ryzen) and save the config, it decreases the size of .config from 169K
> to under 13K, losing almost every setting in the file.

Hmm ... this sound too light for a desktop kernel.  I have done the same, 
stripping out anything not relevant or wanted on my laptop's AMD kernel and 
this is what I get:

$ ls -la /usr/src/linux/.config
-rw-r--r-- 1 root root 106014 Jul 31 17:13 /usr/src/linux/.config

However, I use menuconfig almost exclusively, but this should not make any 
difference.

Did you diff the old and new .config files?  [1]


> Even stranger, if I look at "Local version - append to kernel release:"
> it still shows the value I had previously set - but that setting
> CONFIG_LOCALVERSION is NOT in .config.  If I close the tool and start
> it again, that setting is now missing and it looks like all settings
> have been reset to the clean starting defaults (i.e., many say "(NEW)"
> 
> Am I missing something here, or might this really be a bug in "make
> xconfig" ?

Have you checked the /usr/src/linux symlink is pointing to the correct kernel 
sources directory?  What you describing is akin to you working on the wrong 
.config file.


> Can anyone else replicate this?  While I don't think it's related to my
> problem getting a non-booting kernel, it certainly has me confused.
> 
> Thanks for helping me confirm what's left of my sanity.
> 
> Jack

I don't have time to replicate it this morning, but in case you're missing 
some simple step in your procedure, try this:

cd /usr/src
ls -la

check the linux symlink is pointing to the desired kernel sources directory.  
If not remove it and re-set it either manually, or by using 'eselect kernel'.

Then copy the running config to the symlinked linux directory, overwriting the 
sources' config file with its default settings.

zcat /proc/config.gz > /usr/src/linux/.config

Now you can go into the linux directory and modify its config:

cd linux
make xconfig

When you're done tweaking things make sure you save your changes before you 

make clean && make && make modules_install && make install

The last bit copies over the kernel for you to /boot if you don't want to do 
this manually or use your own naming convention.

For more details have a look here:

https://wiki.gentoo.org/wiki/Kernel/Configuration

HTH.
-- 
Regards,

Mick