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[Qemu-devel] [Bug 1790617] Re: Version of disk image format not exhibite
From: |
Daniel Berrange |
Subject: |
[Qemu-devel] [Bug 1790617] Re: Version of disk image format not exhibited using the 'qemu-img info' command |
Date: |
Tue, 04 Sep 2018 10:54:15 -0000 |
There's no concept of versions for "raw" images as there's no metadata
at all - its just raw disk content.
For the qcow2 format, the version 2 vs version 3 distinction is not
something that is intended to be exposed externally. A version 3 format
file is still handled by the qcow2 format driver, and there is no qcow3
driver.
At an end user level you can specify a compatibility level "0.10" vs
"1.1" which indicates what QEMU version your image shuld be compatible
with - from 'man qemu-img':
"compat"
Determines the qcow2 version to use. "compat=0.10" uses the
traditional image format
that can be read by any QEMU since 0.10. "compat=1.1" enables
image format extensions
that only QEMU 1.1 and newer understand (this is the default).
Amongst others, this
includes zero clusters, which allow efficient copy-on-read for
sparse images.
Internally, compat=1.1, will cause qemu to use qcow2 version 3, but
that's not something users should be concerned with.
Docs that talk about version 2 vs version 3 should be fixed as that's
not something user should be exposed to. They should just talk about the
compat level.
** Changed in: qemu
Status: New => Invalid
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https://bugs.launchpad.net/bugs/1790617
Title:
Version of disk image format not exhibited using the 'qemu-img info'
command
Status in QEMU:
Invalid
Bug description:
OS: Fedora (64 bits) – Linux –. Last available component: qemu-
img.x86_64 2:2.11.2-2.fc28
Description: version of disk image format not exhibited using the
'qemu-img info' command.
Command 'qemu-img info qcow2 [image-file-name.img]' produces this stderr
message:
qemu-img: Expecting one image file name
Try 'qemu-img --help' for more information
How to reproduce in terminal:
1. Create a VM using Raw disk image format
2. Run either commands 'qemu-img info -f raw [image-file-name.img]',
'qemu-img info [image-file-name.img]'.
3. Run either commands 'qemu-img info -f qcow2 [image-file-name.qcow2]',
'qemu-img info [image-file-name.qcow2]'.
Actual result: output model resulting from step .2 exhibits following
informations:
image: image-file-name.img
file format: raw
virtual size: _G (_ bytes)
disk size: _G
Output model resulting from step .3 exhibits following informations:
image: image-file-name.qcow2
file format: qcow2
virtual size: _G (_ bytes)
disk size: _G
cluster_size: _
Snapshot list:
ID TAG VM SIZE DATE VM CLOCK
1 snapshot1 _G 2018-07-31 18:27:49 00:03:45.890
Format specific information:
compat: 1.1
lazy refcounts: true
refcount bits: 16
corrupt: false
Actual result: raw and qcow2 formats respective versions –which are
likely to be mentioned as "version"– to be exhibited.
Additional information: in documentation lastly updated 2018-08-23 at
https://access.redhat.com/documentation/en-
us/red_hat_enterprise_linux/7/html/virtualization_deployment_and_administration_guide/index
it is stated in chapters:
14.10 – 'images in raw format can be resized in both directions, whereas
qcow2 version 2 or qcow2 version 3 images can be grown';
14.12 – 'the qcow2 version supplied with Red Hat Enterprise Linux 7 is 1.1',
'To know which version you are using, run qemu-img info qcow2
[imagefilename.img] command.'.
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