qemu-img cannot be used if filenames contain a ':'

[Robie Basak]

I cannot use qemu-img to create a qcow2 format file with a name containing a colon (':')

Steps to reproduce:

1) qemu-img create -f qcow2 foo 1 # this works
2) qemu-img create -f qcow2 foo:bar 1 # this fails

Expected results: both commands should succeed, and I should end up with files "foo" and "foo:bar".
Actual results: the second command fails with the error: qemu-img: Unknown protocol 'foo:bar'

Affected:
qemu-utils 1.0+noroms-0ubuntu14.10
qemu-utils 1.5.0+dfsg-3ubuntu3

The root cause seems to be in qemu-img.c:print_block_option_help which calls bdrv_find_protocol(filename). This leads to block.c:bdrv_find_protocol which has the following comment:

    /*
     * XXX(hch): we really should not let host device detection
     * override an explicit protocol specification, but moving this
     * later breaks access to device names with colons in them.
     * Thanks to the brain-dead persistent naming schemes on udev-
     * based Linux systems those actually are quite common.
     */

Impact: this stops me using libvirt to import an image into a file-backed storage pool with a libvirt name containing a colon (':'), since libvirt maps these to files in the filesystem, and then qemu-img (or kvm-img as libvirt uses) fails on it. Thus I can't use libvirt storage volumes with colons in the name. I'm doing this to map product IDs in the new Ubuntu cloud image simplestreams naming scheme (and product IDs contain colons).

I also tried: qemu-img create -f qcow2 file://foo 1
But this just leads to: open("file://foo", O_WRONLY|O_CREAT|O_TRUNC, 0644) = -1 ENOENT (No such file or directory)

Workaround: qemu-img create -f qcow2 ./foo:bar 1 works on 1.5.0+dfsg-3ubuntu3, but not on 1.0+noroms-0ubuntu14.10. This may be related to: http://lists.nongnu.org/archive/html/qemu-devel/2013-07/msg01654.html

[Scott Moser (smoser)]

i marked fix-released as in saucy you can do:
 $ qemu-img create ./foo:bar 1
 Formatting './foo:bar', fmt=raw size=1

or
 $ qemu-img create $PWD/foo:bar 1
 Formatting '/tmp/foo:bar', fmt=raw size=1

both of these are reasonable work arounds, but do not work on precise.

[Serge Hallyn (serge-hallyn)]

Sounds like we might need commit

98289620e0460fa595581020ab20127da4a2fc44 block: Don't parse protocol from file.filename

which says

    This allows opening relative file names that contain a colon.

[Serge Hallyn (serge-hallyn)]

Although note that saucy doesn't have that patch either. Hm.

[Steve Langasek (vorlon)]

The Precise Pangolin has reached end of life, so this bug will not be fixed for that release