Thank you for the clarification. Regards, Bharath
On Wed, Aug 7, 2019 at 10:16 PM Daniel P. Berrangé <berra...@redhat.com> wrote: > On Wed, Aug 07, 2019 at 09:57:02PM +0530, bharath paulraj wrote: > > Hi Team, > > > > I am doing a small testing and I don't know if my expectation is correct > or > > not. Pardon me if I am ignorant. > > I created a VM and the VM is running. In the hypervisor I have created > > ".img" file and attached this .img file to the VM. > > My expectation is that, if VM is writing files to the attached disk, then > > it should reflect in the .img file created in the hypervisor. But It is > not > > working as my expectation. > > Please correct me if my expectation is wrong. > > > > Steps: > > 1. Created disk.img in the hypervisor using the command: dd if=/dev/zero > > of=disk.img bs=1M count=50; mkfs ext3 -F disk.img > > 2. Attached the disk to the running VM using the command: virsh > attach-disk > > <Domain-Name> --source disk.img --target vdb --live > > 3. In the VM, I mounted the disk and created few files. > > 4. In the hypervisor, I mounted the disk.img to check if the file created > > in the VM exists in the .img file. > > >> I am not able to see those files. > > Do *NOT* do step 4 - it is incredibly dangerous in general and may well > result in filesystem corruption & serious data loss. > > Most filesystems are only designed to be used by a single OS at any time. > > By mounting it on the host, you have 2 separate OS both accessing the > same filesystem. Even if you mount a filesystem with the read-only > flag, there can still be writes to the filesystem as the second OS to > mount will see it "dirty" and try to replay the journal that reflects > what the first OS was doing. > > Assuming you didn't actually corrupt your FS image, the likely reason > you don't see the file from the host is that the guest OS probably hasn't > flushed it out to disk yet - it'll still be cached in memory in the guest > unless something explicitly ran 'sync'. > > Regards, > Daniel > -- > |: https://berrange.com -o- > https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- > https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- > https://www.instagram.com/dberrange :| > -- Regards, Bharath
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