Anthony Liguori wrote:
Mark Williamson wrote:
I have just recently discovered the XEN VMM and am trying to
familiarize
myself with it. I'm a newbe at it, so bear with me.
No probs, here goes...
I'd like to install an O/S onto a guest virtual machine. Domain 0
is RHEL4
on Xen 2.0.7. My question is how I would go about installing from a
set of
distribution CD's (say RHEL4 or SUSE9) into a file-backed VMM. Can
anyone
help me out with this?
Installing into a file-backed VBD from a distro CD is tricky.
Actually, if you use QEMU to install the distro into a raw disk, and
you only create one partition on the disk, you should be able to just
use a command like this:
That's actually getting to be a preferred method here, at least for some
folks.
qemu file-backed installs allow you to use an existing RHEL installer,
without much fuss or mess, the tricky bit is finding the filesystem
afterward, as what qemu produces is a _partitioned_ file with
filesystems within it.
dd skip=63 bs=512 if=qemu.img of=xen.img
Keep in mind, I've not tried this myself :-)
Exporting the qemu image as /dev/hda in domU and just setting your
parameters right seems to work well and is much simplier.
Are you doing this with the qemu partitioned file itself?
The procedure I've worked up is:
1. Create a target install file. Creating this as a sparse file saves
blocks on disk until you actually need them:
dd if=/dev/zero of=rhel4_qemu bs=1024k seek=$(( 6 * 1024 )) count=0
The $(( 6 * 1024 )) gives you 6 GB to work with, the seek means it's
sparse, and the count=0 means there's only one block used on disk
2. Install RHEL flavor of your choosing. You can boot either from an
install CD, _or_ an ISO image corresponding to same:
qemu -cdrom <cd drive or ISO image> -boot c rhel4_qemu
Walk through the installation. Your image file (rhel4_qemu) will
automatically be partitioned.
3. Shut down qemu after the install is completed.
4. Find out the image file's partitioning. fdisk's '-u' option gives
output in sectors. This helps in the next step. Sample partition
table:
$ /sbin/fdisk -lu rhel4
You must set cylinders.
You can do this from the extra functions menu.
Disk rhel4: 0 MB, 0 bytes
255 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Device Boot Start End Blocks Id System
rhel4p1 * 63 208844 104391 83 Linux
rhel4p2 208845 401624 96390 82 Linux swap
/ Solaris
rhel4p3 401625 4192964 1895670 83 Linux
Ignore the cylinder messages (they matter if you're going to modify
the partition table).
The start sector times the blocksize (512 bytes) gives you the
partition offset in bytes. This is used if you want to loopback
mount the filesystems to copy them someplace else, which you do.
The first partition is /boot, the second is /. I didn't use logical
volumes, though it's possible to do so, complicating matters
somewhat more.
5. Loopback mount the qemu images, creating a couple of mountpoints.
Using the file I'm referencing above (rhel4):
mkdir mp1 mp2
su -c 'mount -o loop,offset=$(( 63 * 512 )) -t ext3 rhel4 mp1'
su -c 'mount -o loop,offset=$(( 4192964 * 512 )) -t ext3 rhel4 mp2'
As a final step, you could copy the contents of these two mountpoints
into a partition or a single filesystem image (a file with just a
filesystem in it, no partitions) which can be used for a Xen file-backed
DomU, etc.
You will have to modify the DomU's /etc/fstab and likely comment the MAC
address registered in /etc/sysconfig/network-scripts/ifcfg-eth0 for
things to work properly.
Once you have a suitable image, you can simply use it as a DomU image
for new deployments.
There are some good related docs on Fedora and Debian installs as well:
https://www.redhat.com/archives/fedora-devel-list/2005-January/msg01320.html
http://www.fedoraproject.org/wiki/FedoraXenQuickstart
Debian: http://hands.com/d-i/HOWTO-xen.txt
--
Karsten M. Self <karsten@xxxxxxxxxxxxx>
XenSource, Inc.
2300 Geng Road #250 +1 650.798.5900 x259
Palo Alto, CA 94303 +1 650.493.1579 fax
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