[SOLVED] Attaching and detaching disk from virtual machine in kvm

fanoflq · 03-08-2017, 06:00 PM

Attaching and detaching disk from virtual machine (vm) in kvm

Code:

#Create file for virtual machine (vm) disk
~ # mkdir -p  /vm-images
~ # dd if=/dev/zero of=/vm-images/vm1-add.img bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 2.20875 s, 486 MB/s

#Add file to centos7-1024ram-minimal-clone.xml
virsh attach-disk centos7-1024ram-minimal-clone /vm-images/vm1-add.img vdb --config                          
Disk attached successfully

#less /etc/libvirt/qemu/centos7-1024ram-minimal-clone.xml
… … 
 <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/var/lib/libvirt/images/centos7-1024ram-minimal-clone.qcow2'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </disk>

    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/vm-images/vm1-add.img'/>
      <target dev='vdb' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
    … … 
…. …. 


# Reboot VM then login and see:
[root@Centos7-1024ram-minimal-clone ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0              11:0    1 1024M  0 rom  
vda             252:0    0   14G  0 disk 
├─vda1          252:1    0  500M  0 part /boot
└─vda2          252:2    0   11G  0 part 
  ├─centos-root 253:0    0   10G  0 lvm  /
  └─centos-swap 253:1    0    1G  0 lvm  [SWAP]
vdb             252:16   0    1G  0 disk            #WORKS!

#exit ssh here.

#Detaching the file disk does not work
# virsh detach-disk centos7-1024ram-minimal-clone /dev/vdb --config                                            
error: No disk found whose source path or target is /dev/vdb

# virsh detach-disk centos7-1024ram-minimal-clone vdb --config                                            
error: No disk found whose source path or target is vdb

What did I missed?
Thank you.

dijetlo · 03-11-2017, 03:43 PM

Try this...

Code:

virsh detach-disk centos7-1024ram-minimal-clone /vm-images/vm1-add.img vdb --config

It looks like you're using the subjective path (the path the VM guest sees) instead of the objective path (the path the VM host sees) when using virsh you're always talking to libvirt on the host, not libvirt on the guest.

fanoflq · 03-11-2017, 05:13 PM

Quote:

Originally Posted by dijetlo

Try this...

Code:

virsh detach-disk centos7-1024ram-minimal-clone /vm-images/vm1-add.img vdb --config

It looks like you're using the subjective path (the path the VM guest sees) instead of the objective path (the path the VM host sees) when using virsh you're always talking to libvirt on the host, not libvirt on the guest.

Thank you.

Code:

$ virsh detach-disk centos7-1024ram-minimal-clone vdb --live --config                                 
Disk detached successfully

dijetlo · 03-11-2017, 11:01 PM

Quote:

Thank you.

Any time, Fanofig.
I've been wanting to learn more about Ovirt and the new KVM platform for a while now, your question gave me impetus to dig back into it, not to mention puzzling out a virsh command string which is always a special kind of fun (as in not really but it's worth practicing anyway)...