Today I wanted to increase the size of a VM, so I did what I always do (have done it before):
qemu-img resize diskimage.qcow2 +22GB
Then the file broke and the VM does not start any more. I tried booting the VM from CD to adjust partitioning but the system will not read the disk any more:
qemu-img check -r all diskimage.qcow2 tcmalloc: large alloc 389841715200 bytes == (nil) @ 0x7fdb4ea66bf3 0x7fdb4ea88488 0x7fdb4e5674a6 0x7fdb50236a37 0x7fdb50236bc8 0x7fdb50237011 0x7fdb5023941e 0x7fdb5023d891 0x7fdb5027848b 0x7fdb5027c196 0x7fdb491efb35 0x7fdb5021ee4d (nil) No errors were found on the image.
No errors? Sounds good, but
virsh start vm does not work and the logs say:
2017-05-21T10:02:30.755824Z qemu-system-x86_64: -drive file=/.../diskimage.qcow2,format=qcow2,if=none,id=drive-virtio-disk0: could not open disk image /.../diskimage.qcow2: qcow2: Image is corrupt; cannot be opened read/write
I tried converting to raw but the conversion fails (exit 1):
qemu-img convert -f qcow2 diskimage.qcow2 -O raw diskimage.raw qcow2: Image is corrupt: L2 table offset 0x2d623039326500 unaligned (L1 index: 0); further non-fatal corruption events will be suppressed qemu-img: error while reading block status of sector 0: Input/output error
The process creates a 354334801920 byte file (much larger than it should have been with +22GB) but it is apparently unusable - when I try to convert it back to qcow2 I get a 200kB file.
Is there a way to extract data from the qcow2 file, or mount it read-write somehow even if there is corruption? I do not have the
nbd kernel module on the machine.