What file(s) does Ubuntu use to track installed Kernels?

Asked by B. C. Schmerker on 2018-05-28

I observed the chain of sbins involved in sudo apt-get [install/upgrade] linux-firmware and sudo dpkg-reconfigure linux-firmware (see also my Bug #1773476 "linux-firmware 1.157.19 attempts to generate /boot/initrd.img-4.8.0-56, /boot/initrd.img-4.8.0 when no corresponding vmlinuz present" in linux-firmware (Ubuntu)). dpkg-reconfigure linux-firmware apparently calls update-initramfs directly, which reports the following warnings, error and fatal attempting to generate /boot/initrd.img-4.8.0(-56):

Ensure all necessary drivers are built into the linux image!
depmod: ERROR: could not open directory /lib/modules/4.8.0(-56): No such file or directory
depmod: FATAL: could not search modules: No such file or directory
depmod: WARNING: could not open /var/tmp/mkinitramfs_*/lib/modules/4.8.0(-56)/modules.order: No such file or directory
depmod: WARNING: could not open /var/tmp/mkinitramfs_*/lib/modules/4.8.0(-56)/modules.builtin: No such file or directory

No false attempts to generate /boot/initrd.img-* occur when [apt/apt-get] [upgrade/dist-upgrade] calls update-initramfs as part of the initramfs-tools trigger processing. The Answer may also clue me to what extent Bug #701578 "purging a kernel sometimes fails to remove kernel in armel" in initramfs-tools (Ubuntu) may be a factor in my Bug #1773476.

Question information

B. C. Schmerker (bcschmerker) said : #1

SOLVED! Seth Forshee identified /var/lib/initramfs-tools as having the data used by update-initramfs. My Bug #1773476 shas therefore been reassigned to initramfs-tools independent of Bug #701578.