[arch-projects] [mkinitcpio] lz4 support

[Dave Reisner]

On Fri, Dec 20, 2013 at 02:58:36AM +0000, Chris Rule wrote:
> Hi, sorry in advance if I haven't reported this correctly. I was hesitant to
> file a bug report until I was sure it is a bug, and what the bug was in.
> 
> I just tested lz4 compression with mkinitcpio after noticing it in the
> conf.pacnew.
> 
> When I rebooted I got the following error after grub and my computer froze:
> [0.<cut>] Initramfs unpacking failed: junk in compressed archive

...

> [0.<cut>] Kernel panic - not syncing: VFS: Unable to mount root fs on

<snip>

> 1) I first found the messages to the linux kernel mailing list adding support
> for lz4 to the kernel, describing it for arm and x86 so I initially assumed lz4
> compressed images weren't supported with x86_64.

x86_64 is still x86.

> 2) I then read the thread (https://code.google.com/p/lz4/issues/detail?id=83)
> linked from the lz4 commit in the mkinitcpio git repository (https://
> projects.archlinux.org/mkinitcpio.git/commit/?id=
> b5927393d103af9b8b2da80e8636b8aa52f80755), although I'm not sure I understood
> everything in that thread I wonder if it may be a bug in lsinitcpio.

lsinitcpio is irrelevant for booting (it's just an analysis/debugging
tool). Anyways, it's just calling the lz4 binary, same as mkinitcpio.

> 3) grub has "insmod gzio" in grub.cfg for all arch menu entries and looking at
> gzio on the grub git it states it is for gzip decompression. I also found
> lzopio.mod in /usr/lib/grub/i386-pc and /usr/lib/grub/x86_64-efi, though I
> can't find any description for it I wonder if grub needs another module for
> decompressing the lz4 ramdisk.

Your bootloader is NOT responsible for decompressing the initramfs. The
first line of your kernel output shows the *kernel* failing to unpack
the initramfs.

> Has a lz4 compressed ramdisk worked for anyone else and if it has can you help
> me rule out any of these options or does anyone think I missed something?

Nope, but this isn't likely to be a bug in mkinitcpio (unless I'm
missing some magical flag, such as --check=crc32 being needed for xz).
I'd talk to lz4 upstream if you want this resolved.

d