root cause of VFS: Cannot open root device "LABEL=/" or unknown-block(0,0)

[Mark Frazer <mark@mjfrazer.org>]

'make install' on the Fedora systems will set grub up to use an initrd.
If you do this with a Linus 2.6 kernel, you will often see this error
when trying to use the initrd:

VFS: Cannot open root device "LABEL=/" or unknown-block(0,0)
Please append a correct "root=" boot option
Kernel panic: VFS: Unable to mount root fs on unknown-block(0,0)

The most common advice given is to change your grub entry to something
like root=/dev/hda2.

What most of the other posts on this topic don't include is the
preceeding messages:
kernel: checking if image is initramfs...it isn't (no cpio magic); looks like an initrd
kernel: Freeing initrd memory: 98k freed
kernel: RAMDISK: Compressed image found at block 0
kernel: RAMDISK: incomplete write (-28 != 32768) 4194304

The root of the problem is that the default ramdisk size of 4096 is not
big enough for the initrd used on Fedora.  I presume the same problem
exists on other systems.

Perhaps the default ramdisk size (CONFIG_BLK_DEV_RAM_SIZE) on the linus
kernels could be increased to 8192.

cheers
-mark
-- 
Drugs are for losers. And hypnosis is for losers with big weird
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