treating logical volumes as physical drives

[Justin Wickett]

I would like to use a logical volume as a "physical" drive on which I  
can install a fedora operating system. As of now, when I run xenguest- 
installer, it treats the install location that I specified ( which is  
an unformatted logical volume that I had just created ) as a physical  
drive (named "xvda") and allows me to perform a basic install on it.  
When I look at that logical volume, it comes up as a "foreign"  
device, because it contains a /boot directory, and a volume group  
consisting of a  / directory and a swap directory. I was wondering  
how to mimic that effect without using my xenguest-installer program,  
so that when I pop a CD in and the installer starts up, I can specify  
a logical volume and let the installer treat it as a physical drive  
just like the xenguest-installer program does.

I am trying to accomplish this because I was unable to install FC4  
via the xenguest-installer. I had mounted the image as a loopback  
device to /var/ftp/pub and specified the /pub directory in FTP  
server's root folder as my "Installation source", and was greeted by  
an error from my FTP server (vsftpd) saying "550 Failed to change  
directory". When I do the exact same thing except mount the FC6 iso  
instead of the FC4 iso, everything works fine. What could I be doing  
wrong?

If all else fails, I guess I can just specify in my /etc/xen/xm- 
fc4-001 file the kernel and the ramdisk parameters, and install FC4  
on an ext3 formatted logical volume specified as the / directory, and  
thus reuse my existing /boot directory instead of trying to use the  
pygrub bootloader with a new /boot directory. In this case, where  
could I find a compiled xenU kernel and an appropriate initrd image  
for FC4?

Thank you very much and happy new years to all!

Justin Wickett
Duke 2010
http://www.duke.edu/~jyw2

[Justin Wickett]

I decided to go with my third approach and ended up installing FC5 on  
an ext3 formatted logical volume within my LVM partition containing  
my host OS (FC6) and specified a FC5 xen PAE-supported kernel in my  
xen config file. The kernel seemed to load without any problems when  
I tried creating the xen config file while in FC6, but panicked since  
I failed to "append a correct "root=" boot option". From the console 

view, I noticed that my kernel command line was  "root=/dev/hda2/dev/ 
VolGroup00/xm_fc5_001_lv ro 4", which obviously doesn't make any  
sense. I followed the basic install for FC6, with the addition of  
creating multiple logical volumes within my LVM partition. What would  
be the correct string to set the root variable found inside of the  
xen config files as?

Here are the last couple of lines I get while in console view before  
the kernel panics...

md: Autodetecting RAID arrays.
md: autorun ...
md: ... autorun DONE.
VFS: Cannot open root device "hda2/dev/VolGroup00/xm_fc5_001_lv" or  
unknown-block(0,0)
Please append a correct "root=" boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown- 
block(0,0)

More of my system information can be viewed at http://www.duke.edu/ 
~jyw2/xenerrors.html

Justin Wickett
Duke 2010
http://www.duke.edu/~jyw2



On Dec 30, 2006, at 4:07 PM, Justin Wickett wrote:

>  I would like to use a logical volume as a "physical" drive
> on which  
>  I can install a fedora operating system. As of now, when I run  
>  xenguest-installer, it treats the install location that I specified  
>  ( which is an unformatted logical volume that I had just created )  
>  as a physical drive (named "xvda") and allows me to perform a basic  
>  install on it. When I look at that logical volume, it comes up as a  
>  "foreign" device, because it contains a /boot directory, and a  
>  volume group consisting of a  / directory and a swap directory. I  
>  was wondering how to mimic that effect without using my xenguest- 
>  installer program, so that when I pop a CD in and the installer  
>  starts up, I can specify a logical volume and let the installer  
>  treat it as a physical drive just like the xenguest-installer  
>  program does.
>
>  I am trying to accomplish this because I was unable to install FC4  
>  via the xenguest-installer. I had mounted the image as a loopback  
>  device to /var/ftp/pub and specified the /pub directory in FTP  
>  server's root folder as my "Installation source", and was greeted  
>  by an error from my FTP server (vsftpd) saying "550 Failed to  
>  change directory". When I do the exact same thing except mount the  
>  FC6 iso instead of the FC4 iso, everything works fine. What could I  
>  be doing wrong?
>
>  If all else fails, I guess I can just specify in my /etc/xen/xm- 
>  fc4-001 file the kernel and the ramdisk parameters, and install FC4  
>  on an ext3 formatted logical volume specified as the / directory,  
>  and thus reuse my existing /boot directory instead of trying to use  
>  the pygrub bootloader with a new /boot directory. In this case,  
>  where could I find a compiled xenU kernel and an appropriate initrd  
>  image for FC4?
>
>  Thank you very much and happy new years to all!
>
>  Justin Wickett
>  Duke 2010
>  http://www.duke.edu/~jyw2
>
>
>
>  --
>  Fedora-xen mailing list
>  Fedora-xen(a)redhat.com
>  https://www.redhat.com/mailman/listinfo/fedora-xen

[Andrew Cathrow]

So looking at your xen config on your web page we see this 


kernel = "/boot/vmlinuz-2.6.18-1.2257.fc5xen"
#initrd = "/boot/initrd-2.6.18-1.2257.fc5xen.img"
memory = "400"
name = "xm-fc5-001"
disk = [ 'phy:/dev/VolGroup00/xm_fc5_001_lv,xvda,w' ]
root = "/dev/hda2/dev/VolGroup00/xm_fc5_001_lv ro"
vif = [ '' ]
#vif = [ 'mac=00:17:3f:23:67:v2, bridge=xenbr0', ]
uuid = "34998936-a8a1-4252-81cc-3109181e8111"
#vnc = 1
#vncunused = 1
vcpus=4
extra = "4"
on_reboot   = 'restart'
on_crash    = 'restart'


Looking at your disk configuration in that file
	disk = [ 'phy:/dev/VolGroup00/xm_fc5_001_lv,xvda,w' ]

So you're using /dev/VolGroup00/xm_fc6_001_lv as your disk in your guest domain.
and that will appear to the guest as /dev/xvda

So the root line is wrong. After the kernel is loaded it'll look inside the guest
domain for /dev/hda2/dev/VolGroup00/xm_fc5_001_lv which doesn't exist.

Typically you'd not have the kernel, initrd and root lines in the xen config.
You'd use a bootloader.
Remove those lines and add the following
	
	bootloader="/usr/bin/pygrub"

Then start the domain with xm create -c domain-name

This will give you a console with a cut down version of grub (that reads
/boot/grub/grub.conf from your guest's xvda device.
This presumes that you've got the xenU kernel installed in the guest domain.





On Sat, 2007-01-06 at 00:27 -0500, Justin Wickett wrote:

>  ~jyw2/xenerrors.html 
-- 

Andrew Cathrow
Red Hat, Inc.

[phone] - Mobile
[phone] - Home Office

acathrow(a)redhat.com

[Justin Wickett]

Thank you Andrew for the response. I am taking the pygrub route, and  
have specified in my xen config file that "disk = [ 'phy:/dev/ 
hdc,xvda,w', 'phy:/dev/VolGroup00/xm_fc5_001_lv,xvda2,w' ]". The  
kernel starts up fine, but when Red Hat nash starts to run, no volume  
groups are found. When i mount /dev/VolGroup00/xm_fc5_001_lv and 'cd'  
into the /dev/ directory, the only files that appear when I do an  
'ls' are mapper and VolGroup00, both of which are directories. I  
think that my problem has to do with specifying a correct value for  
my 'disk' variable in the xen config file. I have included all of the  
important information concerning this issue on my website. As always,  
thanks for the help!

Also, if there was simply a way you could tell Anaconda to treat a  
logical volume as a partition on which to install a standard FC  
operating system all my problems would be solved. I just specified xm- 
fc5-001_lv as my root partition and used my existing FC6 boot  
partition for my /boot kernels+data.

The errors and extra info can be found at http://www.duke.edu/~jyw2/ 
xenerrors.html


Justin Wickett
Duke 2010
http://www.duke.edu/~jyw2



On Jan 6, 2007, at 11:32 AM, Andrew Cathrow wrote:

>  So looking at your xen config on your web page we see this
>
>  kernel = "/boot/vmlinuz-2.6.18-1.2257.fc5xen" #initrd = "/boot/ 
>  initrd-2.6.18-1.2257.fc5xen.img" memory = "400" name =
> "xm-fc5-001"  
>  disk = [ 'phy:/dev/VolGroup00/xm_fc5_001_lv,xvda,w' ] root = "/dev/ 
>  hda2/dev/VolGroup00/xm_fc5_001_lv ro" vif = [ '' ] #vif =  
>  [ 'mac=00:17:3f:23:67:v2, bridge=xenbr0', ] uuid = "34998936- 
>  a8a1-4252-81cc-3109181e8111" #vnc = 1 #vncunused = 1 vcpus=4 extra  
>  = "4" on_reboot = 'restart' on_crash    = 'restart' Looking at
> your  
>  disk configuration in that file disk = [ 'phy:/dev/VolGroup00/ 
>  xm_fc5_001_lv,xvda,w' ] So you're using /dev/VolGroup00/ 
>  xm_fc6_001_lv as your disk in your guest domain. and that will  
>  appear to the guest as /dev/xvda So the root line is wrong. After  
>  the kernel is loaded it'll look inside the guest domain for /dev/ 
>  hda2/dev/VolGroup00/xm_fc5_001_lv which doesn't exist. Typically  
>  you'd not have the kernel, initrd and root lines in the xen config.  
>  You'd use a bootloader. Remove those lines and add the following  
>  bootloader="/usr/bin/pygrub" Then start the domain with xm create - 
>  c domain-name This will give you a console with a cut down version  
>  of grub (that reads /boot/grub/grub.conf from your guest's xvda  
>  device. This presumes that you've got the xenU kernel installed in  
>  the guest domain. On Sat, 2007-01-06 at 00:27 -0500, Justin Wickett  
>  wrote:
> > ~jyw2/xenerrors.html
>  -- Andrew Cathrow Red Hat, Inc. [phone] - Mobile (404) 437  
>  6178 - Home Office acathrow(a)redhat.com