experiment: Leave initramfs

Added experiment on booting past initramfs. It uses Makefile to build initramfs.

1 files changed, 52 insertions, 0 deletions

diff --git a/experiments/03_20251130_leaving_initramfs/Makefile b/experiments/03_20251130_leaving_initramfs/Makefile
new file mode 100644
index 0000000..c55cc00
--- /dev/null
+++ b/experiments/03_20251130_leaving_initramfs/Makefile
@@ -0,0 +1,52 @@
+special_dirs := proc sys
+_special_dirs := $(patsubst %,initramfs/%,$(special_dirs))
+
+pkgs := $(wildcard pkgs/*.deb)
+pkgs_dirs := $(patsubst %.deb,%,$(pkgs))
+pkgs_content := $(patsubst %.deb,%/data.tar.xz,$(pkgs))
+pkgs_unpacked := $(patsubst pkgs/%/data.tar.xz,initramfs/%.unpack,$(pkgs_content))
+
+all : initrd.cpio.gz
+
+initrd.cpio.gz : clean_initramfs initramfs unpack $(_special_dirs) links initramfs/init
+	cd initramfs && find . | cpio -o -H newc | gzip > ../initrd.cpio.gz
+
+initramfs :
+	mkdir initramfs
+
+initramfs/init : init
+	cp $< $@
+	chmod 0755 $@
+
+unpack : $(pkgs_unpacked)
+
+initramfs/%.unpack : pkgs/%/data.tar.xz initramfs
+	tar xf $< -C initramfs
+
+$(_special_dirs) :
+	mkdir -p $@
+
+%/data.tar.xz : %.deb %
+	ar x $< --output "$(@D)"
+
+pkgs/% : pkgs/%.deb
+	mkdir $@
+
+links :
+	ln -s usr/bin    	initramfs/bin
+	ln -s usr/sbin   	initramfs/sbin
+	ln -s usr/lib    	initramfs/lib
+	ln -s usr/lib64  	initramfs/lib64
+#	ln -s bin/sh     	initramfs/init
+	ln -s /proc/mounts	initramfs/etc/mtab
+
+clean_initramfs :
+	rm -rf initramfs
+
+clean : clean_initramfs
+	rm -rf $(pkgs_dirs)
+	rm initrd.cpio.gz
+
+.PHONY : all clean clean_initramfs unpack links
+.SECONDARY :
+.DEFAULT : all