ThunderKernel ramdisks

Ramdisk source trees for the Samsung Galaxy Ace i (GT-S5830i, codename cooperve, BCM21553 platform), one per supported ROM:

• CM7/ - CyanogenMod 7
• CMX/ - CyanMobile X
• Stock/ - Stock Samsung ROM

Each directory is the exact layout of a ramdisk as it should appear when extracted into a boot.img: init*, sbin/, res/, etc. at the top level.

Packing a ramdisk

git can only track file modes as 644/755/120000 (symlink), so the checked-out permissions in these directories are close but not exactly what a real device needs - notably sbin/ and everything under it should be 0750 (not world-executable), and data/ should be 0771. Don't rely on the working tree's on-disk modes; always pack through the script below, which reapplies the exact permission scheme verified against a known-good ThunderKernel 2.2 boot.img (root:root ownership throughout):

Path	Mode
sbin/ (dir) and everything under it	0750
data/ (dir)	0771
init, init.rc, init.bcm21553.rc, init.charge.rc, init.goldfish.rc	0750
any other directory	0755
any other file	0644

python3 pack_ramdisk.py <CM7|CMX|Stock> <output.lzma>

# e.g.
python3 pack_ramdisk.py CM7 out/cm7_ramdisk.lzma
python3 pack_ramdisk.py CMX out/cmx_ramdisk.lzma
python3 pack_ramdisk.py Stock out/stock_ramdisk.lzma

This produces an Android-style newc cpio archive (matching what mkbootfs produces) compressed with LZMA - the format this kernel/ramdisk combination needs, not the more common gzip. Requires xz (brew install xz if it isn't already on your PATH).

.gitignore/.DS_Store placeholder files (only present so git tracks otherwise-empty mountpoint directories like dev/, proc/, sys/, tmp/, data/) are automatically excluded from the packed archive.

Building a boot.img

Once you have a compiled zImage (from the android_kernel_cooperve_thunder repo) and a packed ramdisk from the step above, combine them with mkbootimg.py:

python3 mkbootimg.py \
  --kernel /path/to/zImage \
  --ramdisk out/cm7_ramdisk.lzma \
  --base 0x81600000 \
  --pagesize 4096 \
  -o boot.img

--base and --pagesize are the values verified against a real, known-working ThunderKernel 2.2 boot.img for this device; the kernel and ramdisk offsets, tags offset, and empty on-image cmdline (this kernel's command line is baked into its defconfig via CONFIG_CMDLINE, not read from the boot image) all default to match that same reference and shouldn't need to be overridden. Rebuilding a boot.img from that reference's own extracted kernel and ramdisk with this script reproduces it byte-for-byte.

Repeat once per ROM to produce CM7, CMX, and Stock boot.img files.

Requirements

• Python 3 (no third-party packages required)
• xz on PATH for LZMA compression (brew install xz on macOS)