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

[Maarten Vanraes <maarten@xxxxx>]

Op donderdag 1 augustus 2013 15:51:29 schreef Ian Campbell:
> 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.

wel pvgrub + eltorito would mean i could boot from iso and install from it, 
directly on a pv guest.

the weird part is that pvgrub works from the grub shell with 
(hd0)/images/xen/vmlinuz + (hd0)/images/xen/initrd.img

but not if you copy them to the host and boot directly from those... how odd?

> > 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.

i'll try to supply those... iinm, it errors out on finding drivers... which is 
weird since that initrd.img contains those drivers since it works with pvgrub 
in the grub shell...

> > any thoughts on how to proceed?
-- 
BA NV
IT & Security

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