Carl-Daniel wrote:
>Um, GRUB works fine for me, even on totally crazy RAID systems
> not yet supported by dmraid. There is a well-kept secret you
> need to know: You can install GRUB just fine IFF you boot
> from a GRUB boot floppy. NEVER (except for trivial configurations)
> use the GRUB shell running under any operating system.
>
>Regards,
>Carl-Daniel
>
Saying that (meaning: "IFF") would mean we would never be able to
install Linux using an installer. That's not true, so don't say it.
Grub needs to have a few things in order to install correctly while
running "any operating system".
1. A formatted and supported partition.
2. The relation between the real-mode device name and the Linux device
name of the partition.
3. Know the device-name (like /dev/bladibla) where the partition-table is
located at
Besides that, a partition, lets say /dev/bladibla2 must be on /dev/bladibla.
So, /dev/mapper/mystripedset1 must be on /dev/mapper/mystripedset
That's a stupid limitation of something that IS really trivial:
(hd0,x) must be on (hd0) (duh!)
I agree that installing grub is don't most safely when running the GRUB
shell in real-mode.
GR,
Gerte
Molle wrote:
>Just did this:
>==========
>grub> device (hd0) /dev/mapper/hpt37x_ehgjaggaf
>grub> root (hd0,5)/boot
>Filesystem type is reiserfs, partition type 0x83
>grub> setup (hd0)
>==========
>and it destroyed my RAID0.
>GRUB is such a piece of crap :-).
>It must be severely broken; since if it just sticked to writing to the
>device I pointed it at (hpt37x_ehgjaggaf) which is a RAID0 "virtual
>disk" / whatever, it should never be able to overwrite metadata out on
>the physical disk.
>Anyway, just wanted to tell you to beware.
>Gerte has a GRUB example on his page where he does setup (hd0,5)
>instead of setup (hd0), perhaps that's how it's meant to work.
>Gah.....
>
Molle,
GRUB is not a piece of crap. It's very very sensible when running it on
"unknown" things like the device-mapper stuff.
My experience is, you should always specify a (correct or in this case
empty) device-map when running grub:
/sbin/grub --device-map=/dev/null
After this grub is completely unaware of any realmode devicenames.
Remember always to specify partitions (like: (hd0,x)) with with the grub
"device" command first and to specify the disk (like: (hd0)) in the last
place!! This is important to make grub understand where to lookup
information about geometry for a specific partition. That's the way grub
works on dmraid.
And don't ever blame me of installing bootloaders into (hd0,5), I never
recommend people to do this.
GR,
Gerte
My last words on bootloaders and device-mapper stuff:
* I'm too busy to fix Saout's patch for Lilo to include straight
mappings. I'm working on OpenAFS and Samba at the moment.
* To make grub more dmraid-friendly, device-map code (asigning realmode
names to /dev names) {c,sh}ould be improved a tiny little bit. It could
be an idea to make it less important in which order device commands are
given on the Grub shell. Auto asinging these names is not very important
as it's not easy to determine if something is dmraid, EVMS or LVM. * To
make dmraid more accepted in the Linux world, we have to find a generic
way of (re-)reading partitiontables and giving names to devices that
might be 'something bootable'.
Device-mapper can turn into something that's used for everything
containing partitions ;)
L8er,
Gerte
