Re: [Xen-users] attach an iso file to a PV guest

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-08-01 at 11:22 +0200, Maarten Vanraes wrote:
> Op woensdag 31 juli 2013 16:56:31 schreef Ian Campbell:
> > On Wed, 2013-07-31 at 17:51 +0200, Maarten Vanraes wrote:
> > > Op woensdag 31 juli 2013 16:41:47 schreef Ian Campbell:
> > > > On Wed, 2013-07-31 at 17:17 +0200, Maarten Vanraes wrote:
> > > > > Op woensdag 31 juli 2013 15:36:39 schreef Ian Campbell:
> > > > > > On Wed, 2013-07-31 at 16:20 +0200, Maarten Vanraes wrote:
> > > > > > > i'm using the xl tools and i want to attach an iso file to a PV.
> > > > > > 
> > > > > > Which version of Xen and what does your guest config file contain?
> > > > > > 
> > > > > > Please can you provide the result of attempting "xl -vvv create
> > > > > > $cfg"
> > > > > > with
> > > > > > your $cfg
> > > > > 
> > > > > thanks to your suggestion to use -vvv i can now see more on what's
> > > > > going
> > > > > on...
> > > > > 
> > > > > this is xen 4.2.2 using the centos repository with kernel:
> > > > > 3.4.46-8.el6.centos.alt.x86_64
> > > > > 
> > > > > 
> > > > > what didn't work:
> > > > > [ ]# xl -vvv block-attach templ-sl6
> > > > > format=raw,vdev=hdb,access=ro,backendtype=tap,devtype=cdrom,target=/pa
> > > > > th/t
> > > > > o/SL-64.iso
> > > > > 
> > > > > output:
> > > > > -----------
> > > > > libxl: debug: libxl.c:3211:libxl_device_disk_add: ao 0x1a09a40:
> > > > > create:
> > > > > how=(nil) callback=(nil) poller=0x1a09aa0
> > > > > libxl: debug: libxl_device.c:245:libxl__device_disk_set_backend: Disk
> > > > > vdev=hdb spec.backend=tap
> > > > > DEBUG libxl__blktap_devpath 37
> > > > > aio:/etc/xen/isos/ScientificLinux/SL-64-
> > > > > x86_64-2013-03-18-Install-DVD.iso
> > > > > libxl: error: libxl.c:1866:device_disk_add: failed to get blktap
> > > > > devpath
> > > > > for 0x1a09bf0
> > > > 
> > > > Weird. There were some oddities with cdrom and/or blktap in 4.2, which
> > > > may be improved in 4.3.
> > > > 
> > > > Can you try without the backendtype=tap bit (just say nothing). I hope
> > > > this will cause libxl to automatically pick something which actually
> > > > works.
> > > > 
> > > > Unless you know you have some specific requirement for blktap this is
> > > > good advice in general.
> > > 
> > > Well, it's because not specifying it, that i tried specifying it...
> > > 
> > > when i didn't specify it, there were 2 extra lines:
> > > 
> > > the first was:
> > > "libxl: debug: libxl_device.c:245:libxl__device_disk_set_backend: Disk
> > > vdev=hdb spec.backend=unknown"
> > 
> > backend=unknown at this stage is ok, I think. At some point there should
> > have been logging (with -vvv) about which bakcned to choose.
> > 
> > > but, this is really some oddity, i never thought that the contents of a
> > > file was inspected before actually adding it to the guest...
> > 
> > It shouldn't be (I'm pretty sure it isn't in fact), I think there is
> > probably some other underlying issue.
> 
> could be
> 
> 
> in any case, i'm attempting to go further with phy and manually using 
> losetup... (i know it's not the best thing)
> 
> however, i'm getting pvgrub not working
> 
> the documentation of pvgrub tells me i should use (cd) and in the grub shell, 
> i can see (cd) as available option with tab completion, but it tells me disk 
> not found.
> 
> so, i tried doing like it was a normal disk, but i found no menu.lst file.
> 
> i also tried 
> extra="kernel=(hd0)/images/xen/vmlinuz initrd=(hd0)/images/xen/initrd.img"
> 
> which didn't work...
> 
> but manually in the grub shell entering
> 
> kernel (hd0)/images/xen/vmlinuz
> initrd (hd0)/images/xen/initrd.img
> root (hd0)
> boot
> 
> that works.
> 
> i found in documentation that pvgrub has el torito, so i don't know what is 
> going on...

el torito doesn't make much sense in a PV world I don't think.

I don't know much about using pvgrub I'm afraid.

> so i also tried mounting the iso, copying the vmlinux and initrd.img and 
> specifying it as kernel/initrd in the xl conf... but that didn't seem to work 
> either...

THat should certainly work, logs and full guest config + console would
be needed to debug any further though I'm afraid.
> 
> 
> any thoughts on how to proceed?



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