How to attach drive to domU

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Recently I needed to add an extra virtual drive to a running domU without downtime.

Note: the domU name here is vm1 and the name of the virtual drive is vm1-data. I use LV-based virtual drives for all the domU's, so the notation I use on the dom0 level is domU_name-partition_name_inside_domU.

Here is what I did.

Contents

Create LV backed virtual drive

lvcreate -L14G -n extra-sw rootvg_dom0
mkfs.ext3 /dev/rootvg_dom0/extra-sw 
e2label /dev/rootvg_dom0/extra-sw /extra

List the existing virtual drives

[root@dom0 ~]# xm block-list vm1
Vdev  BE handle state evt-ch ring-ref BE-path
51712    0    0     4      6      8     /local/domain/0/backend/vbd/17/51712  
51728    0    0     4      7      9     /local/domain/0/backend/vbd/17/51728

Attach the new LV-based virtual drive

[root@dom0 ~]# xm block-attach vm1 phy:/dev/rootvg_dom0/extra-sw xvdc r

And now list the drives again to see that the attach operation worked as expected: 

[root@dom0 ~]# xm block-list vm1
Vdev  BE handle state evt-ch ring-ref BE-path
51712    0    0     4      6      8     /local/domain/0/backend/vbd/17/51712  
51728    0    0     4      7      9     /local/domain/0/backend/vbd/17/51728  
51744    0    0     4      9      971   /local/domain/0/backend/vbd/17/51744

Now inside the domU

Here is what I have in the /etc/fstab for the extra drive. Mind you, I was using e2label to label the new drive: 

LABEL=/extra            /extra                  ext3    defaults,ro     1 1

Now, I just mount it and get on with it: 

[root@vm1 ~]# mount /extra
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