RE: Question about skipping virDomainDiskDefAssignAddress

From: Laine Stump <laine(a)laine.org&gt; To: Libvirt <libvir-list(a)redhat.com&gt; Cc: Motohiro Kawahito <JL25131(a)jp.ibm.com&gt;, "Daniel P. Berrangé" <berrange(a)redhat.com&gt; Date: 2021/07/17 00:01 Subject: [EXTERNAL] Re: Question about skipping

On 7/16/21 8:51 AM, Daniel P. Berrangé wrote: > On Fri, Jul 16, 2021 at 09:49:40PM +0900, Motohiro Kawahito wrote: >>> From: "Daniel P. Berrangé" <berrange(a)redhat.com&gt; >>> To: Motohiro Kawahito <JL25131(a)jp.ibm.com&gt; >>> Cc: libvir-list(a)redhat.com >>> Date: 2021/07/16 17:22 >>> Subject: [EXTERNAL] Re: Question about skipping >> virDomainDiskDefAssignAddress >>> >>> On Fri, Jul 16, 2021 at 01:01:50PM +0900, Motohiro Kawahito wrote: >>>>> From: "Daniel P. Berrangé" <berrange(a)redhat.com&gt; >>>>> To: Motohiro Kawahito <JL25131(a)jp.ibm.com&gt; >>>>> Cc: libvir-list(a)redhat.com >>>>> Date: 2021/07/16 00:42 >>>>> Subject: [EXTERNAL] Re: Question about skipping >>>> virDomainDiskDefAssignAddress >>>>> >>>> >>>>> With the exception of paravirtualized Xen guests, this field in >>>>> libvirt XML is *completely* independant of the guest assigned >>>>> device name. >>>>> >>>>> eg the XML might say /dev/vda, but the guest might decde to >>>>> call it /dev/sda, or /dev/whatever or really absolutely >>>>> anything. >>>> >>>> Thank you very much for this information! I understand it. >>>> However, I don't understand how we can pass the target device >> information >>>> (e.g. 0A80) without an error. Do you know how to do it? >>>> >>>> My question was not good, so I opened another thread (How do we >> specify >>>> disk device names for non-Linux VMs in XML?). >>> >>> There is nothing that needs passing. The guest OS decides its naming >>> however it wants to. >> >> We need to control device number from user. This device number would

>> used later, such as detach-disk. Can we pass device number from

> > Detach-disk requires the same information that is provided when the > disk is first configured in libvir. This is completely separate to the > device number / name seen inside the guest. To expand on that, in the case of detaching a disk, you could 1) provide

the target dev in the XML you give to "virsh detach-device", 2) give the

target dev name that you provided in the original XML when you call "virsh detach-disk", or 3) you could specify a custom alias in the original XML ("<alias name='ua-somename'/>" - note that the leading "ua-" is *required* for a custom alias name) and then give that same alias to "virsh detach-device-alias". All three will allow you to reliably select the disk you want, and have the same result.