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Bug 1406981 - guestfish failed to launch nbd qcow2 image with --format=qcow2
Summary: guestfish failed to launch nbd qcow2 image with --format=qcow2
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: libguestfs
Version: 7.4
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: rc
: ---
Assignee: Richard W.M. Jones
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2016-12-22 01:30 UTC by Xianghua Chen
Modified: 2016-12-22 11:59 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2016-12-22 11:59:21 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
log.nbd-qcow2 (8.58 KB, text/plain)
2016-12-22 01:30 UTC, Xianghua Chen 		no flags Details
View All

Description Xianghua Chen 2016-12-22 01:30:26 UTC 
Created attachment 1234583 [details]
log.nbd-qcow2

Description of problem:
guestfish failed to launch nbd qcow2 image with --format=qcow2

Version-Release number of selected component (if applicable):
libguestfs-1.32.7-3.el7.x86_64

How reproducible:
100%

Steps:
1. Prepare a nbd server on fedora: 10.66.9.95
# modprobe nbd

Prepare a qcow2 guest image：
$ qemu-img info RHEL-Server-7.2-64-hvm.qcow2
image: RHEL-Server-7.2-64-hvm.qcow2
file format: qcow2
virtual size: 8.0G (8589934592 bytes)
disk size: 2.2G
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

$ qemu-nbd RHEL-Server-7.2-64-hvm.qcow2 -t

2. On rhel7 client：
# guestfish -a nbd://10.66.9.95 -i
libguestfs: error: could not auto-detect the format when using a non-file protocol.
If the format is known, pass the format to libguestfs, eg. using the
'--format' option, or via the optional 'format' argument to 'add-drive'.


# guestfish --format=qcow2 -a nbd://10.66.9.95 -i -v -x
... ...
ibguestfs: error: could not create appliance through libvirt.
Try running qemu directly without libvirt using this environment variable:
export LIBGUESTFS_BACKEND=direct
Original error from libvirt: internal error: process exited while connecting to monitor: 2016-12-21T08:25:14.437395Z qemu-kvm: -drive file=nbd:10.66.9.95:10809,format=qcow2,if=none,id=drive-scsi0-0-0-0,cache=writeback: could not open disk image nbd:10.66.9.95:10809: Image is not in qcow2 format [code=1 int1=-1]
libguestfs: clear_socket_create_context: setsockcreatecon failed: NULL: Invalid argument [you can ignore this message if you are not using SELinux + sVirt]
libguestfs: trace: launch = -1 (error)



If I use --format=raw it'll be ok：
# guestfish --format=raw -a nbd://10.66.9.95 -i


Please check the -v -x log in attachment.



Actual results:
The first 2 command in step2 all failed.

Expected results:
The guestfish with --format=qcow2 or with no --format should all work.
The guestfish with --format=raw should not work.


Additional info:
# qemu-img info nbd://10.66.9.95
image:
file format: raw
virtual size: 8.0G (8589934592 bytes)
disk size: unavailable

Seems like qemu's problem？
But libguestfs should detect it without using --format or have other workaround for this.
Comment 1 Richard W.M. Jones 2016-12-22 11:59:21 UTC 
This is correct and not a bug.  The qemu-nbd process opens the
qcow2 file and serves it as a raw file.  On the client side (libguestfs)
you therefore have to access it as raw.
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