boot from backup copy of fc5 on usb external disk? [solved]

[jackson byers]

feb 17 2009 success booting fc5copy on usb external disk
 thanks to Mikkel for pointing me in  right direction

this fc5copy was not an install, but rather a backup copy of my
mainfc5 on a scsi disk   on sda1

for days i was getting "cant find /dev/root....  kernel panic"

finally fixed that with proper mkinitrd see below

then was  getting  cant access resume device /dev/sda2  for days
now understand that occuring bc of disk reordering

part of my problem was using reisrfs on the usb, but ext3 on mainfc5 on sda1
this required an extra  --preload=reiserfs  in mkinitrd cmd
and a further editing of the mkrootdev line  in the initrd  init file.

root at bootp ~]# mkdir cleanrs2; cd cleanrs2
[root at bootp cleanrs2]# mkinitrd --preload=ehci-hcd  --preload=usb-storage
--preload=reiserfs   /boot/initrd_usbrs2.img 2.6.17-1.2174_FC5

expand:
[root at bootp cleanrs2]# gunzip -c initrd_usbrs2.img |cpio -i
5551 blocks
[root at bootp cleanrs2]# ls
bin  dev  etc  init  initrd_usbrs2.img  lib  proc  sbin  sys  sysroot

now modify the mkrootdev line
from
mkrootdev -t ext3 -o defaults,ro /dev/sda1
to
mkrootdev -t reiserfs -o defaults,ro /dev/sdc1

repack:
[root at bootp cleanrs2]# find . |cpio -c -o |gzip -9 >../initrd_usbrs2.img

at this point, still getting  "cant access resume device /dev/sda2"
but no longer getting caught in "cant find /dev/root"

next problem  was getting caught in filesytem check on  sda1,sda3
which eventually forced a reboot,  but no kernel panic!
The sda1,sda3 problems evidently bc of reordering of the disks (see below)
I got around this gotcha by
commenting out the sda1, sda3 lines in the usb fstab

my mainfc5 grub.conf has following stanza for the usb boot

title FC5copy (2.6.17-1.2174_FC5_usbrs2.img)  /media/disk-1 (hd1,2)
      root (hd1,2)  ## sdb3
      kernel /boot/vmlinuz-2.6.17-1.2174_FC5 ro root=LABEL=rootusb  rhgb
quiet
      initrd /boot/initrd_usbrs2.img


when booted up from usb:
fdisk clearly shows disks have been reordered

[root at bootp ~]# fdisk -l

Disk /dev/sda: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1       30401   244196001   83  Linux  <<<<was sdc1

Disk /dev/sdb: 36.7 GB, 36703934464 bytes
255 heads, 63 sectors/track, 4462 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *           1        2676    21494938+  83  Linux  <<< was
sda1,2,3
/dev/sdb2            2677        3163     3911827+  82  Linux swap / Solaris
/dev/sdb3            3164        4462    10434217+  83  Linux

so to get swap working need  /dev/sdb2 instead of  /dev/sda2  in usb fstab


Disk /dev/sdc: 36.7 GB, 36703934464 bytes
255 heads, 63 sectors/track, 4462 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1   *           1          13      104391   83  Linux  <<<was sdb1-7
/dev/sdc2              14         268     2048287+  82  Linux swap / Solaris
/dev/sdc3             269         281      104422+  83  Linux
/dev/sdc4             282        4462    33583882+   f  W95 Ext'd (LBA)
/dev/sdc5             282        1301     8193118+  83  Linux
/dev/sdc6            1302        2321     8193118+  83  Linux
/dev/sdc7            2322        4462    17197551   83  Linux
[root at bootp ~]#

if want mainfc5 (on sda1) mounted when boot  from usb
need
/dev/sdb1  /fc5hold    in usb fstab

finally i think i have fixed the "cant find resume device"

i changed the fstab swap line to use sdb2 in place of sda2
but it seemed to require
rebooting twice for it to take effect

at this point, my usb backup copy of  my mainfc5(which is on a scsi disk)
is booting without complaint


The only thing i cant do is to have the fc5copy /boot  found on the usb,
evidently bc my bios cant see the usb disk

so my fc5copy /boot was copied to  sdb3  -->  root (hd1,2)  in grub.conf

this is  just a holding tank for the /boot files:
I am not treating it as a "separate /boot partition", not listed in fstab

regards,
Jack
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