Is there a specific reason why the focus is on trying to shoe-horn
everything possible into the initrd.img and then compress rather than
winnow out the files an installed system will never need to find the
root file-system?
I tackled the issue of ever-expanding host-generated initrd.img file
sizes when they began hitting 80MB+ back in 2018 and since then have
carried my own patches that reduce sizes by not including files the host
will not need.
One small change that brings major benefits is only including the
firmware files required, not every file declared by a kernel module. The
GPU drivers are the main culprit there with amdgpu declaring over 500 of
which, for any individual GPU, only a handful are relevant, but
Plymouth's pulling in multiple GPU drivers doesn't help that.
Statistics (initrd.img with kernel v6.2.4):
MODULES= FIRMWARE_LOADED size MOST DEP firmwares build-time
most false 77117694 634 14.49
most true 60302859 -22% 8 11.99
dep false 42489938 -45% 606 6.84
dep true 25704125 -66% -40% 8 6.35
FIMWARE_LOADED=true relies on a simple kernel patch which I've been
meaning to upstream that writes "Firmware loaded: <file>" for each.
$ journalctl --dmesg | grep 'Firmware loaded' | head -n 15
Jul 02 11:42:21 sunny kernel: firmware_class: Firmware loaded: reporting
Jul 02 11:42:21 sunny kernel: radeon 0000:0a:00.0: Firmware loaded:
radeon/verde_pfp.bin
Jul 02 11:42:21 sunny kernel: radeon 0000:0a:00.0: Firmware loaded:
radeon/verde_me.bin
Jul 02 11:42:21 sunny kernel: radeon 0000:0a:00.0: Firmware loaded:
radeon/verde_ce.bin
Jul 02 11:42:21 sunny kernel: radeon 0000:0a:00.0: Firmware loaded:
radeon/verde_rlc.bin
Jul 02 11:42:21 sunny kernel: radeon 0000:0a:00.0: Firmware loaded:
radeon/verde_mc.bin
Jul 02 11:42:21 sunny kernel: radeon 0000:0a:00.0: Firmware loaded:
radeon/verde_smc.bin
Jul 02 11:42:21 sunny kernel: radeon 0000:0a:00.0: Firmware loaded:
radeon/TAHITI_uvd.bin
Jul 02 11:42:21 sunny kernel: radeon 0000:0a:00.0: Firmware loaded:
radeon/TAHITI_vce.bin
Jul 02 11:42:22 sunny kernel: r8152 2-8.3:1.0: Firmware loaded:
rtl_nic/rtl8153a-4.fw
Jul 02 11:42:28 sunny kernel: platform regulatory.0: Firmware loaded:
regulatory.db
Jul 02 11:42:28 sunny kernel: platform regulatory.0: Firmware loaded:
regulatory.db.p7s
My experiments and patches are documented at
https://iam.tj/projects/ubuntu/initramfs-tools/
The main take is the question:
Is MODULES=most really the best default for installed-on-host images (it
obviously is for installer and portable images). If it can be nuanced
then =DEP plus winnowing the firmware files gives great gains with
minimal effort.
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