Re: [Xen-devel] How is a file-backed FreeBSD filesystem mounted for a FreeBSD XenU?

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> Now, since the system isn't in production yet I'd like to show a FreeBSD
> XenU instance running so that I can show the rest of the staff to convince
> them of the benefits of running Xen servers, even if they insist on
> continuing to run FreeBSD for all servers.

Cool :-)

> I've examined the XenDemo CD and the FreeBSD filesystem and XenU there, but
> for the life of me I cannot figure out how the FreeBSD filesystem (on the
> CD as /freebsd.fs) is handed to the FreeBSD XenU kernel to be mounted.


> I've been able to mount the /root.fs filesystem under FC4 ("mount -o loop
> root.fs /debian.root"), but that doesn't work for the /freebsd.fs file,
> even using the "-t ufs -o ufstype=44bsd" options.  I also don't know how to
> mount it on our FreeBSD systems.

Just a guess: if the FreeBSD rootfs is sliced (BSD partitions) then won't 
Linux have trouble mounting it?

> 1) How is /freebsd.fs hooked to the FreeBSD XenU on the XenDemo CD?  If I
> know how this is done I can do a quick demo of a FreeBSD XenU on our Linux
> FC4 system.

The same way you'd hook a disk file to a Linux domU: add a 
'file:/blah/blah/foo,target_dev,w' to the disks line in the config file.  I'm 
not sure what syntax is supported for specifying the target dev for FreeBSD.  
the FreeBSD config file on the demo CD should be useful as a template.

Doing this causes the file to be attached as to a block loop in dom0 - this 
block device is then exported to BSD, which can use it like any other block 
device.

I'd suggest that to start with you copy the filesystem image from the demo CD, 
tweak the config file from the CD and then try and start a domain using that.

Does that answer your question?

Cheers,
Mark

> 2) An alternative method would be to use an NFS mounted root filesystem
> served from one of our FreeBSD servers.  The easiest and quickest
> filesystem to use would be the /freebsd.fs or Kip Macy's mdroot file system
> from http://www.fsmware.com/xenofreebsd/5.3/.  How do you mount a file-back
> filesystem under FreeBSD?
>
> Thank you much,
>
> David Schmidt
> NOC Analyst - Northwest Open Access Network
> dschmidt@xxxxxxxxxx  1-866-662-6380
>
> There are 10 types of people in this world.  Those that understand binary
> and those that do not.
>
>
>
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