initramfs: add initial emlinux-initramfs-base recipe

[hiromotai7]

Purpose

Added a new INITRD recipe.

Test

Comfirmed the following:

1. An initrd.img is generated by using the emlinux-initramfs-base recipe when IMAGE_INITRD is defined in local.conf.
2. no differences between the file list inside the generated initrd.img and of the original initrd.img.

Test results

1. Confirming initrd.img creation

Add the following line to local.conf.

MACHINE = "qemu-arm64"
TMPDIR .= "-${DISTRO}"
IMAGE_INITRD = "emlinux-initramfs-base"

Run bitbake emlinux-image-base twice:

1. DISTRO = "emlinux-bookworm" in conf/local.conf
2. DISTRO = "emlinux-trixie" in conf/local.conf

confirmed that the initrd.img was generated and that it uses the name of the INITRD recipe.

• ${INITRD_RECIPE_NAME}-${DISTRO}-${MACHINE}-initrd.img

$ (cd tmp-emlinux-bookworm/deploy/images/qemu-amd64; ls *.img)
emlinux-initramfs-base-emlinux-bookworm-qemu-amd64-initrd.img
$ (cd tmp-emlinux-trixie/deploy/images/qemu-amd64; ls *.img)
emlinux-initramfs-base-emlinux-trixie-qemu-amd64-initrd.img

2. Compare the file list inside initrd.img

The original produces 2 initrd files.

1. emlinux-image-base-emlinux-bookworm-qemu-arm64-initrd.img
2. emlinux-image-base-emlinux-trixie-qemu-arm64-initrd.img

Compared them respectively.

emlinux-bookworm

Ran the following commands for comparison.
No differences found.

$ diff -u \
  <(cd     emlinux-image-base-emlinux-bookworm-qemu-arm64-initrd; find . | sort)
  <(cd emlinux-initramfs-base-emlinux-bookworm-qemu-arm64-initrd; find . | sort)
$ 

emlinux-trixie

Ran the following commands for comparison.
No differences found.

$ diff -u \
  <(cd     emlinux-image-base-emlinux-trixie-qemu-arm64-initrd; find . | sort)
  <(cd emlinux-initramfs-base-emlinux-trixie-qemu-arm64-initrd; find . | sort)
--- /dev/fd/63	2026-04-10 20:21:04.691966357 +0900
+++ /dev/fd/62	2026-04-10 20:21:04.691966357 +0900
@@ -91,6 +91,7 @@
 ./usr/lib/aarch64-linux-gnu/libcrypt.so.1
 ./usr/lib/aarch64-linux-gnu/libcrypt.so.1.1.0
 ./usr/lib/aarch64-linux-gnu/libc.so.6
+./usr/lib/aarch64-linux-gnu/libdevmapper.so.1.02.1
 ./usr/lib/aarch64-linux-gnu/libkmod.so.2
 ./usr/lib/aarch64-linux-gnu/libkmod.so.2.5.1
 ./usr/lib/aarch64-linux-gnu/libmount.so.1
@@ -103,6 +104,8 @@
 ./usr/lib/aarch64-linux-gnu/libseccomp.so.2
 ./usr/lib/aarch64-linux-gnu/libseccomp.so.2.6.0
 ./usr/lib/aarch64-linux-gnu/libselinux.so.1
+./usr/lib/aarch64-linux-gnu/libudev.so.1
+./usr/lib/aarch64-linux-gnu/libudev.so.1.7.10
 ./usr/lib/aarch64-linux-gnu/libz.so.1
 ./usr/lib/aarch64-linux-gnu/libz.so.1.3.1
 ./usr/lib/aarch64-linux-gnu/libzstd.so.1
@@ -232,15 +235,19 @@
 ./usr/lib/udev/rules.d
 ./usr/lib/udev/rules.d/50-firmware.rules
 ./usr/lib/udev/rules.d/50-udev-default.rules
+./usr/lib/udev/rules.d/55-dm.rules
 ./usr/lib/udev/rules.d/60-block.rules
+./usr/lib/udev/rules.d/60-persistent-storage-dm.rules
 ./usr/lib/udev/rules.d/60-persistent-storage.rules
 ./usr/lib/udev/rules.d/71-seat.rules
 ./usr/lib/udev/rules.d/73-special-net-names.rules
 ./usr/lib/udev/rules.d/75-net-description.rules
 ./usr/lib/udev/rules.d/80-drivers.rules
 ./usr/lib/udev/rules.d/80-net-setup-link.rules
+./usr/lib/udev/rules.d/95-dm-notify.rules
 ./usr/lib/udev/scsi_id
 ./usr/sbin
 ./usr/sbin/blkid
+./usr/sbin/dmsetup
 ./usr/sbin/modprobe
 ./usr/sbin/rmmod
$ 

Since the differences are identical to those in the two original files as below and no files were missing, I consider this to be acceptable.

1. emlinux-image-base-emlinux-bookworm-qemu-arm64-initrd.img
2. emlinux-image-base-emlinux-trixie-qemu-arm64-initrd.img

[masami256]

do we need dmsetup by default?

[hiromotai7]

That's because dmsetup was included in the emlinux-bookworm initramfs by default, However, these packages were not present in the emlinux-trixie initramfs.

Since verified filesystem is becoming more common in embedded systems for security, I think we should keep them in unless there's a specific reason not to.

[masami256]

@hiromotai7 The *.img file name is changed from emlinux3 branch

build@0ffcf73155cf:~/work/build$ find tmp-orig/deploy/images/ -name "*.img"
tmp-orig/deploy/images/qemu-amd64/emlinux-image-base-emlinux-bookworm-qemu-amd64-initrd.img
tmp-orig/deploy/images/qemu-arm64/emlinux-image-base-emlinux-bookworm-qemu-arm64-initrd.img
build@0ffcf73155cf:~/work/build$ find tmp/deploy/images/ -name "*.img"
tmp/deploy/images/qemu-amd64/emlinux-initramfs-base-emlinux-bookworm-qemu-amd64-initrd.img
tmp/deploy/images/qemu-arm64/emlinux-initramfs-base-emlinux-bookworm-qemu-arm64-initrd.img

note:

'*.img' files in tmp-orig directory were built with head of emlinux3 branch.
'*.img' files in tmp directory were built with this pr's commit.

[hiromotai7]

Sorry. I have not verified the boot on Raspberry PI or Generic-x86_64 with new initramfs yet.
I will submit the MR again after confimrming those as well.