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Re: rescue bootable cd ???



On Tue, Oct 02, 2007 at 07:08:11AM -0500, helices wrote:
 
> Unfortunately, both systems on which I experienced such calamity ran lvm
> over software raid 5.  In fact, both systems ran lilo, not grub; and
> everything was under lvm, including root and boot.  Under these
> circumstances, there is specific configuration information missing, and
> that prevents the debian install cd, and knoppix, from being able to
> read my disks ;<

I thought that grub's support of LVM and any raid other than raid1
wasn't either supported or ready for prime-time?

> 
> When I started this thread, I was thinking about the olden days, when I
> (tried to remember to) ma[dk]e a boot floppy after each new kernel ;>

Bootfloppies aren't an option due to the size of the kernel and
ramdisks.

Here's my suggestion:

I hope you have good backups:

reinstall,

raid1 partition for /boot
	or if your drives are big enough anyway, just a 400 or 500 MB /
	on raid1.  Put the same partition at the beginning of each of
	your drives and put them all into the raid1 array.  That way, no
	single drive failure can cause failure of your /boot or /

If you must use raid5 for the rest, OK, but since drives are cheap, I'd
suggest raid1.

Use LVM overtop of this second raid array, one LV for each of the
standard partitions (/usr, /home/, /var, possibly /tmp [or use tmpfs for
/tmp]).

Use Grub.

Install grub in the MBR of all drives.

Manually put an entry in grub that looks to each drive in the raid1
array (with co-responding root= kernel option if / is on raid1 instead
of LVM).

In this way, any single drive failure will still allow a full boot.  

If you need the performance of raid0 across a raid1 (non /boot,
preferably non / too), e.g. for /var or /home, make new LVs after
install that do striping.

Good luck,

Doug.



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