Re: [PLUG] reuse old os partition

["Paul L. Snyder" <plsnyder@drexel.edu>]

Quoting Stephen Gran <steve@lobefin.net>:

> On Thu, Jan 13, 2005 at 01:26:56PM -0500, Art Alexion said:
> > After a couple of months of testing Debian-based Ubuntu, I am ready to
> > abandon my old red hat OS partition.  (the red hat home directories
> > have their own partitions)
> > 
> > What is the best way to do that? cfdisk or just a reformat?  
> 
> rm -rf?  It's up to you - both Debian and RedHat use the same
> filesystems, so you could either reformat, or just blow away.
> 
> > what changes to grub?  Just delete the red hat entry from the
> > menu.list, or do I have to get rid of the boot images of the red hat
> > system somehow?
> 
> Just deleting the entries from menu.lst should do it, AIUI.

Yep.  A little detail, if you're interested in digging deeper:

grub has two stages, the first stage of which is typically stored in
your Master Boot Record.  When you power up your system, the BIOS
scuttles around looking for a boot sector.  Eventually (after it has
determined that you don't have a flopppy inserted, etc.), it will load
the MBR from your hard drive, and pass control to the grub boot sector
stored there.

The grub boot sector then loads the second stage boot loader.  (Well,
it usually passes control to a "stage 1.5" that knows how to deal
with the type of partition where stage 2 is stored, which then passes
control to stage 2.)  Stage 2 is the interactive boot loader, and it
reads your boot configurations out of grub.conf.  (grub.conf is the
new name for menu.lst...menu.lst is a symlink on most newer systems.)

Stage 2 can then either load the specified kernel (Linux, *BSD,
multiboot-compatible) or pass control to a different boot loader stored
in a partition's boot sector. (This latter is called chain-loading, and
is how you'd go about setting up a Linux/Windows dual-boot system.)

So, remnants of Red Hat might lurk in the form of:

 * an entry in your grub.conf/menu.lst (edit to delete)

 * a partition boot sector on the Red Hat partition (unlikely, as you
   probably installed it to the MBR)

 * a partition label.  I believe that Red Hat uses partition labels to
   try to abstract the underlying hardware device names used in fstab.
   If it's an ext2/3 partition, you can use e2label /dev/hdaX or
   dumpe2fs /dev/hdaX to see if a label is assigned.  Actually, you can
   also use this to determine the UUID of the partition, which is
   probably a better way to specify a particular partition if you're
   trying to avoid device filenames.  (Play around with findfs to see
   label/UUID partition location in action, e.g.,

     dumpe2fs -f /dev/hda1 | grep UUID

   to discover the UUID, and
   
     findfs UUID=(whatever the uuid was)

   to go the reverse direction.)  Tweak labels and UUIDs with tune2fs.
   Try mount -U.

 * and, of course, all the Red Hat files stored in the file system.
   rm -rf

As suggested, reformatting the partition (mke2fs -j /dev/hdaX, or some
such) will wipe out everything but the grub.conf entry (which is stored
on your /boot partition), including any label or partition boot sector.

pls
___________________________________________________________________________
Philadelphia Linux Users Group         --        http://www.phillylinux.org
Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
General Discussion  --   http://lists.phillylinux.org/mailman/listinfo/plug