[sf-lug] About USB partitioning and formatting

[Ken Shaffer]

Hi Jim, Here's some notes on initial ram disks -- using them has simplified
in the last few years.
Ken

Initial Ram Disk Notes

Examining the initrd from a 4g stick and one from a usb hard disk showed no
significant difference.  The usb hard disk initrd worked
in booting a 4g stick.  My previous booting problems I now attribute to
wrong grub devices.

The initrd may be examined with the cpio command on post FC3 systems.
Uncompress the initrd with "gzip -cd" or "zcat", and pipe to cpio to
list the contents.
zcat initrd... |cpio  --list

Older systems use the loopback device:
mkdir temp ; cd temp
cp /boot/initrd.img ./initrd.img.gz
gunzip initrd.img.gz
mount -t ext -o loop initrd.img /mnt/initrd
ls -la /mnt/initrd

Newer systems just unzip and use cpio to create files in a directory:
mkdir myird
cd myird
zcat /boot/initrd.img-2.6.31-16-generic |cpio -iv --make-directories

>From the top level of the initrd directory, you may recreate the
initrd by:
find ./ |cpio -H newc -o >../myrd
cd ..
gzip myrd

The newc format (-H newc) is required to boot, the default (bin) fails to
work.

In the init script on the top level, I changed the initial init message, and
started a /bin/sh just after the depmod -a in init. There was a pause of 20
seconds, then the shell became active, which allowed me to look around the
live ramdisk directories. When I exited, the boot sequence continued. If you
remove the "quiet" on the grub.cfg (menu.lst) kernels, you can see the
progress of the boot -- The lower case "ok"s are from the initram scripts,
and the upper case "OK"s are from the root file system scripts.

The initrd contents varies depending upon the type of system you have. The
Fedora Core systems tend to have directories like /proc and /sys set up, but
Ubuntu (9.04 at least), creates such directories on the fly from the initial
scripts.  In either case, the first thing run is /init.
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