[woody-discussion] cramfs - compressed rom fs
Ive just been playing with cramfs, which is a compressed rom fs included
in the 2.3.x series.
I made a cramfs image with the same contents as the current root.img,
cramfs doesnt support hard links, so i converted them to soft links.
root.img (zipped) is 963018 Bytes
cramfs img is 1081344 Bytes
I tried testing it, i dd'ed the image to a floppy and copyed a 2.3
kernel with compressed rom fs support built into the kernel to the
rescue disk.
The rescuedisk booted, loaded the root img, but then after init started
busybox gave an error saying i didnt have enough memory, i have 64MB
which is plenty.
Maybe busybox doesnt like read only filesystems, i dont know. Ive heard
devfs is really needed to use a rom rootfs, ihavent played with devfs
yet....
Compressed root romfs should be technically possible, wether its worth
it is another question.
ADVANTAGES to root cramfs
1) lowmem machines could use a floppy as a rootfs instead of a ramdisk
2) a rom root fs would provide a more generic base for booting from
other mediums e.g. CD's
DISADVANTAGES to root cramfs
1) Size, takes up over 10% more space from the rootfs medium.
2) Speed, ramdisk based rootfs will always be more responsive than
rootfs on disk/floppy or anywhere else.
Im not sure wether cramfs is a good idea, but seems as i checked it out
i thought i may as well report on my experience.
Glenn McGrath
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