Discussion about the files in the /boot and initrd #1731

ader1990 · 2024-03-06T09:03:44Z

This PR was opened to have a place where to discuss line by line on the files that we can or cannot remove from the /boot partition and initrd. Or maybe move them into the /usr.

This is a follow up on @pothos suggestion to cut things we do not need: flatcar/Flatcar#1381 (comment)

How the data was compiled:

# Content of the /boot partition for AMD64 built from
# flatcar/scripts commit a842366ed9a2c2b1204a87f8563ef09e2950e5e3
tree -sifF  /boot | sort -k2 -rn

# Main data
$: df | grep '/boot'
/dev/vda1          129039      64135      64905  50% /boot

$: file flatcar_production_image.vmlinuz
flatcar_production_image.vmlinuz: Linux kernel x86 boot executable bzImage, version 6.6.17-flatcar ([email protected]) #1 SMP PREEMPT_DYNAMIC Mon Mar  4 18:50:2A

$: du flatcar_production_image.vmlinuz
56124   flatcar_production_image.vmlinuz

Added another commit with the initrd contents.

How the data was compiled:

bash extract-initramfs-from-vmlinuz.sh flatcar_production_image.vmlinuz vmlinuz
cd vmlinuz/
tree -sifF . | sort -k2 -rn

pothos · 2024-03-06T09:46:22Z

Thanks, we can also discuss the kernel config: https://alpha.release.flatcar-linux.net/amd64-usr/current/flatcar_production_image_kernel_config.txt

github-actions · 2024-03-06T09:46:35Z

Build action triggered: https://github.com/flatcar/scripts/actions/runs/8419352317

jepio · 2024-03-06T09:46:55Z

boot_partition.txt

+[     783864]  ./flatcar/grub/x86_64-efi/core.efi.signed*
+[     783864]  ./EFI/boot/grubx64.efi*
+[     782336]  ./flatcar/grub/x86_64-efi/core.efi*


these are all the same file and i want to say that we only need EFI/boot/grubx64.efi, but this needs testing.

Unless we would also remove them in the update postinst hook these would still occupy space to prevent an update - but even then for some old clients the postinst hook might be too late because the kernel can't even be extracted to /boot.

pothos · 2024-03-06T09:52:20Z

initrd.txt

+[    2058480]  ./rootfs-1/usr/lib/systemd/libsystemd-core-252.so*
+[    1933576]  ./rootfs-1/usr/lib64/libc.so.6*
+[    1845305]  ./rootfs-1/usr/lib/firmware/phanfw.bin
+[    1649076]  ./rootfs-1/usr/lib/firmware/mellanox/mlxsw_spectrum-13.2010.1006.mfa2


In theory we could the network firmware and kernel modules from /sysusr/usr but it needs some wrangling to have them available at the right time…

jepio · 2024-03-06T09:53:16Z

boot_partition.txt

+[     470624]  ./xen/pvboot-x86_64.elf*
+[     470624]  ./flatcar/grub/x86_64-xen/core.elf*


Same file, and i'm not convinced pvboot elf works. Hasn't been tested in years/ever.

pothos · 2024-03-06T09:56:35Z

initrd.txt

@@ -0,0 +1,1397 @@
+[   12539904]  ./rootfs-0/kernel/x86/microcode/GenuineIntel.bin


The microcode updates can be delayed by defining a service that does echo 1 > /sys/devices/system/cpu/microcode/reload (see https://www.kernel.org/doc/Documentation/x86/microcode.txt) once we would symlink/copy them to /lib/firmware/{intel-ucode,amd-ucode} in the initrd from /sysusr.

pothos · 2024-03-06T09:59:38Z

initrd.txt

+[    1167440]  ./rootfs-1/usr/sbin/nvme*
+[    1145040]  ./rootfs-1/usr/lib64/libgcrypt.so.20.4.3*
+[    1127648]  ./rootfs-1/usr/lib/firmware/mellanox/mlxsw_spectrum3-30.2010.1006.mfa2
+[    1038064]  ./rootfs-1/usr/sbin/btrfs*


That binary could be symlinked to /sysusr/, same for xfs* and mkfs.* stuff and even ip and mdadm

pothos · 2024-03-06T10:01:11Z

initrd.txt

+[     267160]  ./rootfs-1/usr/lib64/libtinfo.so.6.4*
+[     266400]  ./rootfs-1/usr/lib64/libsmartcols.so.1.1.0*
+[     265300]  ./rootfs-1/usr/lib/firmware/ql2400_fw.bin
+[     254499]  ./rootfs-1/usr/share/ca-certificates/ca-certificates.crt


Small win, but that file could be symlinked.

pothos · 2024-03-06T10:03:52Z

My impression is that we should start with the big stuff: find a way to load network firmware and kernel modules, and CPU microcode update from /sysusr/usr/.

jepio · 2024-03-06T09:57:34Z

initrd.txt

can you also check how well individual files compress? this might make a big difference

this means if the files we d like to move/remove have a great compression rate, it does not make too much sense to remove them?

the initrd is compressed with some algorithm (zstd i think), and so we would want to focus on files that are big when compressed so that removing them actually has the desired impact. Otherwise we might remove a file that looks big but doesn't give much benefit because it compresses to something really small.

initrd.txt

jepio · 2024-03-06T10:02:43Z

initrd.txt

+[     814776]  ./rootfs-1/usr/lib64/libsepol.so.2*
+[     812616]  ./rootfs-1/usr/sbin/xfs_db*
+[     785272]  ./rootfs-1/usr/lib64/libzstd.so.1.5.5*
+[     745872]  ./rootfs-1/usr/sbin/xfs_repair*


i dont think we have anything that would call xfs_repair from the initrd

…rrent/flatcar_production_image_kernel_config.txt

ader1990 · 2024-03-06T10:17:54Z

Thanks, we can also discuss the kernel config: https://alpha.release.flatcar-linux.net/amd64-usr/current/flatcar_production_image_kernel_config.txt

Added this file for discussion.

flatcar_production_image_kernel_config.txt

ader1990 · 2024-03-25T11:29:04Z

I will keep in this updated comment a log of the AMD64 /boot partition size history, to have a clear picture on the size increase over time:

# 2024-03-12, Flatcar HEAD https://github.com/flatcar/scripts/commit/89cca15171f0b2424a4c132bb0c2138159b7eb6e
/dev/sda1         129039       59962      69078  47% /boot
# 2024-03-18, Flatcar ALPHA 3913.0.0 https://alpha.release.flatcar-linux.net/amd64-usr/3913.0.0/
/dev/sda1         129039       61753     67287  48% /boot
# 2024-03-25, Flatcar HEAD https://github.com/flatcar/scripts/commit/6ebffa7a4fde3a1b2c8d362b065b35b4ce3a43e4
/dev/sda1         129039       62503     66536  49% /boot

ader1990 added 2 commits March 6, 2024 09:00

add /boot partition contents ordered by size

c3ce61c

add initrd contents ordered by size

bcef0f9

jepio reviewed Mar 6, 2024

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pothos reviewed Mar 6, 2024

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jepio reviewed Mar 6, 2024

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pothos reviewed Mar 6, 2024

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jepio reviewed Mar 6, 2024

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added kernel config from alpha.release.flatcar-linux.net/amd64-usr/cu…

fa64cd5

…rrent/flatcar_production_image_kernel_config.txt

ader1990 commented Mar 6, 2024

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flatcar_production_image_kernel_config.txt Show resolved Hide resolved

ader1990 mentioned this pull request Mar 6, 2024

initrd_size_decrease: remove mlxsw_spectrum/mlxsw_core kernel modules #1734

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ader1990 mentioned this pull request Mar 15, 2024

[RFE] Flatcar boot partition size shrink effort flatcar/Flatcar#1381

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github-actions bot mentioned this pull request Mar 22, 2024

Monthly contributions report 2024-02-22 - 2024-03-21 flatcar/Flatcar#1398

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ader1990 mentioned this pull request Mar 25, 2024

Enable Intel I225/I226 driver (igc) #1786

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ader1990 had a problem deploying to development April 5, 2024 10:17 — with GitHub Actions Failure

ader1990 mentioned this pull request May 30, 2024

Unable to update Flatcar server - /boot full flatcar/Flatcar#1461

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Discussion about the files in the /boot and initrd #1731

Discussion about the files in the /boot and initrd #1731

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ader1990 commented Mar 25, 2024 •

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		[ 470624] ./xen/pvboot-x86_64.elf*
		[ 470624] ./flatcar/grub/x86_64-xen/core.elf*

		@@ -0,0 +1,1397 @@
		[ 12539904] ./rootfs-0/kernel/x86/microcode/GenuineIntel.bin

Discussion about the files in the /boot and initrd #1731

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