mainline kernel builds more recent than 5.11.16 are busted on ubuntu 20.10 / 20.04 (LTS)

[Kevin Hester]

I just noticed that recent mainline kernel installs fail on my ubuntu 20.10 machine. Builds <= 5.11.16 work fine. Newer builds (5.11.17 or 5.12.1) fail to install with

" linux-headers-5.12.1-051201-generic depends on libc6 (>= 2.33); however:
  Version of libc6:amd64 on system is 2.32-0ubuntu3."

This seems to be an accidental regression because there is nothing in the core 5.11.17 kernel that changed to require glibc 2.33 (rather than the older 2.32) (I think?).

See the following half workaround by someone on stack overflow for good info on the possible root cause: https://askubuntu.com/a/1335849/285965

Did something inadvertently change in the build environment where you create mainline? Could you possibly change it back?

Full log follows:

```
mainline --install 5.12.1
mainline 1.0.14
Distribution: Ubuntu 20.10
Architecture: amd64
Running kernel: 5.11.15-051115-generic
Fetching index from kernel.ubuntu.com...
OK
----------------------------------------------------------------------
Found installed: 5.11.16-051116.202104211235
Found installed: 5.9.16-050916.202012211331
Found installed: 5.11.15-051115.202104161034
Found installed: 5.8.18-050818.202011011237
Found installed: 5.8.0-45.51
----------------------------------------------------------------------
----------------------------------------------------------------------
Preparing to install '5.12.1'
Selecting previously unselected package linux-headers-5.12.1-051201-generic.
(Reading database ... 360725 files and directories currently installed.)
Preparing to unpack .../linux-headers-5.12.1-051201-generic_5.12.1-051201.202105021030_amd64.deb ...
Unpacking linux-headers-5.12.1-051201-generic (5.12.1-051201.202105021030) ...
Selecting previously unselected package linux-headers-5.12.1-051201.
Preparing to unpack .../linux-headers-5.12.1-051201_5.12.1-051201.202105021030_all.deb ...
Unpacking linux-headers-5.12.1-051201 (5.12.1-051201.202105021030) ...
Selecting previously unselected package linux-image-unsigned-5.12.1-051201-generic.
Preparing to unpack .../linux-image-unsigned-5.12.1-051201-generic_5.12.1-051201.202105021030_amd64.deb ...
Unpacking linux-image-unsigned-5.12.1-051201-generic (5.12.1-051201.202105021030) ...
Selecting previously unselected package linux-modules-5.12.1-051201-generic.
Preparing to unpack .../linux-modules-5.12.1-051201-generic_5.12.1-051201.202105021030_amd64.deb ...
Unpacking linux-modules-5.12.1-051201-generic (5.12.1-051201.202105021030) ...
dpkg: dependency problems prevent configuration of linux-headers-5.12.1-051201-generic:
 linux-headers-5.12.1-051201-generic depends on libc6 (>= 2.33); however:
  Version of libc6:amd64 on system is 2.32-0ubuntu3.

dpkg: error processing package linux-headers-5.12.1-051201-generic (--install):
 dependency problems - leaving unconfigured
Setting up linux-headers-5.12.1-051201 (5.12.1-051201.202105021030) ...
Setting up linux-modules-5.12.1-051201-generic (5.12.1-051201.202105021030) ...
Setting up linux-image-unsigned-5.12.1-051201-generic (5.12.1-051201.202105021030) ...
I: /boot/vmlinuz.old is now a symlink to vmlinuz-5.11.16-051116-generic
I: /boot/initrd.img.old is now a symlink to initrd.img-5.11.16-051116-generic
I: /boot/vmlinuz is now a symlink to vmlinuz-5.12.1-051201-generic
I: /boot/initrd.img is now a symlink to initrd.img-5.12.1-051201-generic
Processing triggers for linux-image-unsigned-5.12.1-051201-generic (5.12.1-051201.202105021030) ...
/etc/kernel/postinst.d/dkms:
 * dkms: running auto installation service for kernel 5.12.1-051201-generic

Kernel preparation unnecessary for this kernel. Skipping...

Building module:
cleaning build area...
make -j8 KERNELRELEASE=5.12.1-051201-generic -C /lib/modules/5.12.1-051201-generic/build M=/var/lib/dkms/acpi-call/1.1.0/build...(bad exit status: 2)
ERROR (dkms apport): kernel package linux-headers-5.12.1-051201-generic is not supported
Error! Bad return status for module build on kernel: 5.12.1-051201-generic (x86_64)
Consult /var/lib/dkms/acpi-call/1.1.0/build/make.log for more information.

Kernel preparation unnecessary for this kernel. Skipping...

Building module:
cleaning build area...
make -j8 KERNELRELEASE=5.12.1-051201-generic -C /lib/modules/5.12.1-051201-generic/build M=/var/lib/dkms/spi-ch341-usb/1.0.0/build modules...(bad exit status: 2)
ERROR (dkms apport): binary package for spi-ch341-usb: 1.0.0 not found
Error! Bad return status for module build on kernel: 5.12.1-051201-generic (x86_64)
Consult /var/lib/dkms/spi-ch341-usb/1.0.0/build/make.log for more information.
   ...done.
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-5.12.1-051201-generic
/etc/kernel/postinst.d/zz-update-grub:
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.12.1-051201-generic
Found initrd image: /boot/initrd.img-5.12.1-051201-generic
Found linux image: /boot/vmlinuz-5.11.16-051116-generic
Found initrd image: /boot/initrd.img-5.11.16-051116-generic
Found linux image: /boot/vmlinuz-5.11.15-051115-generic
Found initrd image: /boot/initrd.img-5.11.15-051115-generic
Found linux image: /boot/vmlinuz-5.9.16-050916-generic
Found initrd image: /boot/initrd.img-5.9.16-050916-generic
Found linux image: /boot/vmlinuz-5.8.18-050818-generic
Found initrd image: /boot/initrd.img-5.8.18-050818-generic
Found linux image: /boot/vmlinuz-5.8.0-45-generic
Found initrd image: /boot/initrd.img-5.8.0-45-generic
Found Windows Boot Manager on /dev/nvme0n1p1@/EFI/Microsoft/Boot/bootmgfw.efi
Adding boot menu entry for UEFI Firmware Settings
done
Errors were encountered while processing:
 linux-headers-5.12.1-051201-generic
E: Installation completed with errors
~/development/meshtastic/spi-ch341-usb$
```

[Torsten Krah (tkrah)]

Latest 20.04 is also affected which has libc6 2.31.

[Cornelius Zwalin (zwalin)]

Probably a duplicate of https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1926938