AW: [Xen-users] Overcoming loopback device limitation - revisited

["Mathias Diehl" <md@xxxxxxxxxxxxx>]

Hi John,

actually I'm not sure about your problem - but here's what I did:

C=8; echo; echo "Creating loop device nodes."; \
   while [ $C -lt 256 ]; do mknod /dev/loop$C b 7 $C; \
   echo -n .; C=`expr $C + 1`; done; echo;

As yo see permissions do not appear. You create your file's to store the
VM's, give them a filesystem and fire them up.

cheers,

Mathias


___
www.evoconcept.de


-----Ursprüngliche Nachricht-----
Von: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx]Im Auftrag von john
maclean
Gesendet: Sonntag, 30. Juli 2006 22:31
An: xen-users@xxxxxxxxxxxxxxxxxxx
Betreff: [Xen-users] Overcoming loopback device limitation - revisited


Hi there chaps,

Just to get me up and running I ran `make world && make install` from
source. All went well until I started running out of loopback devices
to create guests. I know of the 8 devices limitation and I'm sure that
the loop "module" is built into the kernel;

 modinfo loop
 filename:       /lib/modules/2.6.16-xen/kernel/drivers/block/loop.ko
 license:        GPL
 alias:          block-major-7-*
 vermagic:       2.6.16-xen SMP 686 gcc-3.3
 depends:
 parm:           max_loop:Maximum number of loop devices (1-256) (int)

OK, that number is more than enough for me. This is a laptop and I'd
want to manage about 12. So I use this boot time parameter even though
I know/think that it's a built in:-

 cat /proc/cmdline
 root=/dev/hda3 ro console=tty0 max_loop=32

To create some more loop back devices I ran the following:-

 for X in $(seq 8 31); do mknod ;  MAKEDEV /dev/loop$X  b 7 $i ; chmod
660 /dev/loop$X; chown 0.disk /dev/loop$X;  done

Now I can only seem to have just one domU running!

#acid~#  xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      512     1 r-----   108.4
vm01                               1       64     1 ------     0.3

acid:~# xm create vm00 -c /etc/xen/vm00
Using config file "/etc/xen/vm00".
Error: Device 769 (vbd) could not be connected. Backend device not found.

I have a few simple-ish questions that I'd a appreciate some answers for;
 - What is the file system that creates loopback devices a required,
on the fly?
 - How do I know if I have this?
 - Did I give the newly created devices the wrong permissons?
 - Why does it appear that all of the /dev/loop devices bar one are
"blocked"?
 - Do I have to do some /etc/udev mojo?

version:- xen-3.0.2-2
arch:- debian sarge
me:- very stuck ;)
--
John Maclean  - 07739 171 531
MSc (DIC)

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