Re: [Xen-users] Can't boot from ISO image...

["Lionel Kernux" <lionel.kernux@xxxxxxxxx>]

Hey Mark,

Thanks alot for the help.

Moving the ISO image to /var/lib/xen/images did the trick concerninig
the cdrom ISO image.

I also tried out tap:aio with no success. I've seen some configs out
there that use tap:aio for the hdd image and so I tried it for my hdd
image without success. The VM halts and complains that ther is no
bootable device.

I'll keep trying on that end.

Thanks again!

M


On Jan 25, 2008 9:54 AM, Mark Williamson <mark.williamson@xxxxxxxxxxxx> wrote:
> > Hmmm...tap:aio you say....I'm googling it....can you reccomend a link
> > to some description and/or explanation of tap:aio?
>
> Not off the top of my head.
>
> Basically, the file:/ syntax uses the loop device, as you know, which has a
> number of drawbacks (including easily running out of loop devices and some
> performance / memory use problems - particularly if you use a file: device on
> an NFS filesystem, which is a really good way of making the OOM killer come
> and attack your processes.)
>
> tap:aio: uses the blocktap driver, which is Xen's userspace driver (with a
> kernelspace portion) for providing access to file-backed VBDs.  The aim of it
> is to give decent performance whilst mitigating the drawbacks of using the
> loopback device.  It also has greater flexibility because blocktap can
> support other VBD formats (e.g. tap:qcow for copy on write disks, although
> I'm not sure what Xen releases that's available in).
>
> I'm not clear what your problem could be, but I'm thinking that tap:aio: may
> help sidestep it, or cast more light on the root cause.
>
> HOWEVER
>
> Regarding your file: problem, I've just had a brainwave.  Do you have SELinux
> enabled?  If so you need to have your ISO under /var/lib/xen/images or it'll
> probably fail to work correctly.  You'll probably find messages about SELinux
> preventing Xend / Xen hotplug scripts from performing the setup operations,
> if you look in /var/log/messages.
>
> Cheers,
> Mark
>
>
> > thanks
> >
> > M
> >
> > On Jan 24, 2008 7:38 PM, Mark Williamson <mark.williamson@xxxxxxxxxxxx>
> wrote:
> > > Do you really need to pass the ISO as a file:/ disk anyhow?  tap:aio is
> > > supposed to be better and maybe it'll solve your problem into the
> > > bargain!
> > >
> > > Cheers,
> > > Mark
> > >
> > > On Thursday 24 January 2008, Lionel Kernux wrote:
> > > > Hi,
> > > >
> > > > I've been trying to boot from a RHEL4 install iso without much luck
> > > > (the xen way).
> > > > The Host is:
> > > > RHEL 5.1
> > > > xen-3.0.3-41.el5
> > > >
> > > > Here is my guest config:
> > > >
> > > > #  -*- mode: python; -*-
> > > > #======================================================================
> > > >==== == # Python configuration setup for 'xm create'.
> > > > # This script sets the parameters used when a domain is created using
> > > > 'xm create'.
> > > > # You use a separate script for each domain you want to create, or
> > > > # you can set the parameters for the domain on the xm command line.
> > > > #======================================================================
> > > >==== ==
> > > >
> > > > import os, re
> > > > arch = os.uname()[4]
> > > > if re.search('64', arch):
> > > >     arch_libdir = 'lib64'
> > > > else:
> > > >     arch_libdir = 'lib'
> > > > kernel = "/usr/lib/xen/boot/hvmloader"
> > > > builder='hvm'
> > > > memory = 1536
> > > > shadow_memory = 8
> > > > name = "symbiosis"
> > > > pae=1
> > > > vif = [ 'type=ioemu, bridge=xenbr0' ]
> > > > disk = [
> > > > 'file:/var/lib/xen/images/symbiosis.img,ioemu:hda,w','file:/root/RHEL4.
> > > >6-x8 6_64-AS-disc1.iso,ioemu:hdc:cdrom,r' ]
> > > > device_model = '/usr/' + arch_libdir + '/xen/bin/qemu-dm'
> > > > boot="d"
> > > > vncunused=0
> > > > vncconsole=1
> > > > vncpasswd='secret'
> > > > stdvga=0
> > > > serial='pty'
> > > > usb=1
> > > > usbdevice='mouse'
> > > >
> > > > I run "xm create symbiosis" and get:
> > > >
> > > > Error: Device 5632 (vbd) could not be connected. losetup -r /dev/loop0
> > > > /root/RHEL4.6-x86_64-AS-disc1.iso failed
> > > >
> > > > But, I can manually attach the loop device like so:
> > > >
> > > > losetup -r /dev/loop# /root/RHEL4.6-x86_64-AS-disc1.iso
> > > >
> > > > No problem.
> > > >
> > > > If I do:
> > > >
> > > > losetup -r /dev/loop5 /root/RHEL4.6-x86_64-AS-disc1.iso
> > > >
> > > > and then in the config file use this:
> > > >
> > > > disk = [
> > > > 'file:/var/lib/xen/images/symbiosis.img,ioemu:hda,w','phy:/dev/loop5,io
> > > >emu: hdc:cdrom,r' ]
> > > >
> > > > It boots off the ISO.
> > > >
> > > > Yes, it seems I can fake it out, but I'd like to get it work
> > > > properly....
> > > >
> > > > Any help?
> > > >
> > > > Thanks
> > > >
> > > > M
> > > >
> > > > _______________________________________________
> > > > Xen-users mailing list
> > > > Xen-users@xxxxxxxxxxxxxxxxxxx
> > > > http://lists.xensource.com/xen-users
> > >
> > > --
> > > Push Me Pull You - Distributed SCM tool
> > > (http://www.cl.cam.ac.uk/~maw48/pmpu/)
>
>
>
> --
>
> Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)
>

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