install grub on LVM

Rick Stevens rstevens at internap.com
Wed Sep 26 16:01:58 UTC 2007 

On Wed, 2007-09-26 at 16:09 +0800, toufique shakh wrote:
> according to me,
> 
> /boot partition cannot be on LVM because bootloaders doesn't understand Lvm logical volumes including lilo grub.
> this is as per Linux LVM-Howto documentation. www.linuxdocs.org.
> please correct me if i am wrong.

That is correct.  Grub also doesn't understand software RAID.  'Tis
always best to put boot on a regular, standard partition.

> > ----- Original Message -----
> > From: "Rick Stevens" <rstevens at internap.com>
> > To: "Getting started with Red Hat Linux" <redhat-install-list at redhat.com>
> > Subject: Re: install grub on LVM
> > Date: Tue, 18 Sep 2007 15:15:15 -0700
> > 
> > 
> > On Tue, 2007-09-18 at 16:23 -0500, Bob McClure Jr wrote:
> > > On Tue, Sep 18, 2007 at 04:10:37PM -0500, Fred Grant wrote:
> > > > On Tue, 2007-09-18 at 10:02 -0500, Bob McClure Jr wrote:
> > > > > On Tue, Sep 18, 2007 at 06:39:20AM -0500, Fred Grant wrote:
> > > > > > I want to install grub on hd1 boot partition which is LVM.
> > > > OK it's not LVM, it's ext3.  I must have been looking at swap.
> > > > > > > hd1?  Do you mean hda?  Or hda1?
> > > > > hda1
> > > > > I didn't think you could boot LVM partitions.  Let's be clear on this.
> > > > > An LVM partition is somewhat like an extended partition in that it
> > > > > does not contain any kind of filesystem.  It does, however, contain
> > > > > one or more logical volumes each of which which may contain a
> > > > > filesystem.
> > > > > > > Customarily, there is (at least) one plain linux partition with an
> > > > > ext[23] filesystem on it, which is designated as the /boot partition.
> > > > > You will likely have another partition, type LVM, which contains one
> > > > > or more logical volumes containing filesystems for /, /home, etc.
> > > > > Still, you would normally install grub on the MBR of that disk, e.g.,
> > > > > for /dev/hda
> > > > > > >   grub-install /dev/hda
> > > > I did this and result is indicated below.
> > >
> > > While booted to FC5?  If so, show us the grub.conf for that system.
> > >
> > > > > Care to share a bit more information about your desired setup?
> > > > ------------
> > > > fdisk:
> > > > Disk /dev/hda: 30.7 GB, 30750031872 bytes
> > > > 255 heads, 63 sectors/track, 3738 cylinders
> > > > Units = cylinders of 16065 * 512 = 8225280 bytes
> > > > >    Device Boot      Start         End      Blocks   Id  System
> > > > /dev/hda1   *           1          13      104391   83  Linux
> > > > /dev/hda2              14        3738    29921062+  8e  Linux LVM
> > > > > Disk /dev/hdb: 61.4 GB, 61492838400 bytes
> > > > 255 heads, 63 sectors/track, 7476 cylinders
> > > > Units = cylinders of 16065 * 512 = 8225280 bytes
> > > > >    Device Boot      Start         End      Blocks   Id  System
> > > > /dev/hdb1   *           1        7288    58540828+  83  Linux
> > > > /dev/hdb2            7289        7476     1510110    5  Extended
> > > > /dev/hdb5            7289        7476     1510078+  82  Linux swap /
> > > > Solaris
> > > > > Disk /dev/dm-0: 29.5 GB, 29527900160 bytes
> > > > 255 heads, 63 sectors/track, 3589 cylinders
> > > > Units = cylinders of 16065 * 512 = 8225280 bytes
> > > > > Disk /dev/dm-0 doesn't contain a valid partition table
> > > > > Disk /dev/dm-1: 1073 MB, 1073741824 bytes
> > > > 255 heads, 63 sectors/track, 130 cylinders
> > > > Units = cylinders of 16065 * 512 = 8225280 bytes
> > > > > Disk /dev/dm-1 doesn't contain a valid partition table
> > >
> > > The above two errors can be ignored.
> > >
> > > > -------------------
> > > > Per the above, I have F5 installed on hda and Ubuntu live cd on hdb.  In
> > > > BIOS I select "boot from HDD1" and boot fails.  If I select "boot from
> > > > HDD2", boot succeeds.  Is it possible that BIOS considers hda to be
> > > > HDD2?
> > >
> > > Could be.  The BIOS will tell you.
> > >
> > > > Can it be toggled?
> > >
> > > In most recent machines, yes.  Look in the BIOS under something like
> > > Boot Order or drive swapping.  Rick has a lot more experience with
> > > that and can probably tell you exactly.
> > 
> > Hoo boy!  It depends on the BIOS.  First, keep in mind that grub doesn't
> > know about hda, hdb, etc. as those are what the Linux kernel calls them.
> > In fact, there is no "hd" stuff in the F7 and later kernels.  All hard
> > drives are treated as SCSI drives and are given the names "sda", "sdb",
> > etc. regardless of their interface type (for example, ATA is really just
> > SCSI over IDE cables).
> > 
> > Now this depends on the specific BIOS involved, but the vast majority
> > give the first bootable hard drive the low-level identifier of 0x80, the
> > second drive 0x81 and so on (this traces back to the old BDOS "int15"
> > calls to the BIOS) and THOSE are what grub relies on (in fact, the old
> > LILO boot loader used the "0x80"-type nomenclature).  While they're
> > called "hd(drive,partition)" in grub's config file, that's just to
> > differentiate hard drives from floppy drives.  You can think of grub's
> > "hd(0,..." as meaning "BDOS device 0x80", and "fd(0,..." means "BDOS
> > device 0x00".
> > 
> > So by changing the boot order in your BIOS, you've forced it to assign
> > your SECOND drive the 0x80 identifier and the FIRST drive the 0x81
> > identifier.  Since Linux inherits the primary drive from the boot loader
> > (and BIOS), it will think your SECOND drive is hda (or sda), and the
> > FIRST drive as hdb (or sdb).
> > 
> > I'm guessing that's probably more than you want to know, but there it
> > is.  ;-)
> > 
> > ----------------------------------------------------------------------
> > - Rick Stevens, Principal Engineer             rstevens at internap.com -
> > - CDN Systems, Internap, Inc.                http://www.internap.com -
> > -                                                                    -
> > -               The Theory of Rapitivity: E=MC Hammer                -
> > -                                  -- Glenn Marcus (via TopFive.com) -
> > ----------------------------------------------------------------------
> > 
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> 
> 
> file:/root/Desktop/449732.png
> 
> 
> 
> 
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----------------------------------------------------------------------
- Rick Stevens, Principal Engineer             rstevens at internap.com -
- CDN Systems, Internap, Inc.                http://www.internap.com -
-                                                                    -
-                      LOOK OUT!!! BEHIND YOU!!!                     -
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