On 2/17/2012 9:54 PM, Matthew Hook wrote:> For those wanting to know how to mount filesystems through blktap2
> here is how you do it, as I couldn''t find it fully documented.
> The instructions on the blktap2 readme file are rather out of date.
>
>
> You can mount them under Dom0 like so.
>
> e.g. to mount a vhd file,
> sudo xm block-attach 0 tap2:vhd:/home/xen/xenwin7-persist.vhd xvdb w 0
>
> Now the device should appear under /dev
>
> ls /dev/xvdb*
> /dev/xvdb /dev/xvdb1 /dev/xvdb2
>
> sudo mount /dev/xvdb2 /mnt
>
> Mounts the first partition on xvdb to the path /mnt
You can also mount with tap-ctl and kpartx, but it''s a little more
complicated:
# tap-ctl allocate
/dev/xen/blktap-2/tapdev7
# tap-ctl spawn
tapdisk spawned with pid 28746
# tap-ctl attach -p 28746 -m 7
# tap-ctl open -p 28746 -m 7 -a aio:/somewhere/some_example_image.img
# kpartx -a /dev/xen/blktap-2/tapdev7
# ls /dev/mapper/tapdev7*
/dev/mapper/tapdev7p1 /dev/mapper/tapdev7p2
# mount /dev/mapper/tapdev7p1 /mnt
# umount /mnt
# kpartx -d /dev/mapper/tapdev7p1
# tap-ctl close -p 28746 -m 7
# tap-ctl detach -p 28746 -m 7
# tap-ctl free -m 7
(Is this a better way? I don''t actually know.)
Note that when using the tap-ctl method in scripts, I''ve found that
it''s
important to intersperse "sync" commands and slight timeouts before
umount/kpart -d/tap-ctl close, as otherwise you will sometimes end up
with the tapdisk2 process hung in an uninterruptible disk sleep and
unable to be queried (causing havoc when it comes to trying to trying to
view the process list). At least, under 4.1.
-John