[libvirt] virDomainAttachDevice error during disk hotplug

[Deepak C Shetty]

On 08/16/2013 06:59 PM, Daniel P. Berrange wrote:
> On Sat, Aug 10, 2013 at 05:38:20PM +0530, Deepak C Shetty wrote:
>> Hi All,
>>      I am trying to do a hotplug of a disk from VDSM (which uses
>> libvirt to get things done).
>> I hit the below error "operation failed: open disk image file
>> failed" comign from virDomainAttachDevice.
>> 1) The qemu-img create  cmd I use (inside vdsm) to create the file
>> being hotplugged is
>>
>> /usr/bin/qemu-img create -f qcow2 -F qcow2 -b /rhev/data-center/000065de-04b8-42e2-986c-2de664708be7/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399
>> /var/run/vdsm/3333017d-1278-4bfb-8129-62bded257399' (cwd
>> /var/run/vdsm)
> So here you're using paths under /rhev or /var/run/vdsm.

Sorry, didn't get your Q here


>
>
>> 2013-08-10 11:19:41.770+0000: 1103: debug :
>> virStorageFileGetMetadataRecurse:939 : path=/home/dpkshetty/libSM_disk/localstoragedomain/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399
> This log suggests those paths are just symlinks into your home
> directory.

Yes, and these are setup by vdsm which sets the entire path with proper 
vdsm.kvm perms. id 'qemu' is also part of 'kvm' group.


>
> What permissions are set on /home/dpkshetty ?  By default $HOME permissions
> will not allow any other user to access files under it. So you would have
> to do  'chmod o+x /home/dpkshetty' to make this work

For instance...

[root at vdsm_tsm_int_f19 vdsm]# ls -l /| grep home
drwxr-xr-x.   3 root root  4096 Aug  8 19:53 home

[root at vdsm_tsm_int_f19 vdsm]# ls -l /home | grep dpk
drwx--x--x. 15 dpkshetty dpkshetty 4096 Aug  9 17:44 dpkshetty

[root at vdsm_tsm_int_f19 vdsm]# ls -l /home/dpkshetty | grep libSM
drwxr-xr-x. 16 dpkshetty dpkshetty 4096 Aug  9 18:36 libSM_disk

If perms weren't rite, qemu says "permission denied"... but this is 
diff, it says "failed to open disk image"
Atleast perms wise I feel i am fine here.

[root at vdsm_tsm_int_f19 vdsm]# su - qemu -s /bin/bash
-bash-4.2$ id
uid=107(qemu) gid=107(qemu) groups=107(qemu),36(kvm) 
context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

-bash-4.2$ qemu-img info /var/run/vdsm/3333017d-1278-4bfb-8129-62bded257399
image: /var/run/vdsm/3333017d-1278-4bfb-8129-62bded257399
file format: qcow2
virtual size: 3.8G (4096000000 bytes)
disk size: 196K
cluster_size: 65536
backing file: 
/rhev/data-center/000065de-04b8-42e2-986c-2de664708be7/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399
backing file format: qcow2

-bash-4.2$ getenforce
Permissive



-bash-4.2$ ls -l 
/rhev/data-center/000065de-04b8-42e2-986c-2de664708be7/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399
-r--r-----. 1 vdsm kvm 197120 Aug 16 12:42 
/rhev/data-center/000065de-04b8-42e2-986c-2de664708be7/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399

-bash-4.2$ qemu-img info 
/rhev/data-center/000065de-04b8-42e2-986c-2de664708be7/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399
image: 
/rhev/data-center/000065de-04b8-42e2-986c-2de664708be7/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399
file format: qcow2
virtual size: 3.8G (4096000000 bytes)
disk size: 136K
cluster_size: 65536


>
> Daniel