Commit 93d1b2cb authored by Nikos Skalkotos's avatar Nikos Skalkotos

docs: Add a different image formats section

Add a section on how to use snf-image-creator on non-raw format images
parent 0d89fb60
......@@ -315,6 +315,106 @@ confirm the provided data.
Choosing *YES* will create and upload the image to your cloud account.
Working with different image formats
====================================
*snf-image-creator* works on raw image files. If you have an image file with a
different image format you can either convert it to raw using
*qemu-img convert* command or use the *blktap* toolkit that provides a
user-level disk I/O interface and use the exposed *tapdev* block device as
input on *snf-image-creator*.
Converting images to raw
------------------------
Converting between images with *qemu-img convert* is generally straightforward.
All you need to provide is the output format (*-O raw*) and an output filename.
You may use the *-f* option to define the input format, but in most cases this
is guessed automatically. The table below shows a list of supported image
formats and the equivalent argument you may pass to the *-f* flag.
+--------------------------+-----------+
|Image Format |-f argument|
+==========================+===========+
|qcow2 (QEMU Copy On Write)|qcow2 |
+--------------------------+-----------+
|VHD (Mircosoft Hyper-V) |vpc |
+--------------------------+-----------+
|VMDK (VMware) |vmdk |
+--------------------------+-----------+
With the following commands we demonstrate how to download and convert an
official Ubuntu 14.04 *qcow2* image to raw:
.. code-block:: console
$ wget http://uec-images.ubuntu.com/trusty/current/trusty-server-cloudimg-amd64-disk1.img
$ qemu-img convert -f qcow2 -O raw trusty-server-cloudimg-amd64-disk1.img ubuntu.raw
Working on .vhd disk images using blktap/tapdisk
------------------------------------------------
If the source image format is *Microsoft VHD* [#f1]_, we can use blktap/tapdisk
to connect it to a block device and use this block device as input in
*snf-image-creator* without having to convert the image to raw format.
Assuming that you work on a recent Debian GNU/Linux, you can install the
needed tools by giving the following command:
.. code-block:: console
# apt-get install blktap-utils
# modprobe blktap
Please refer to your distribution's documentation on how to install the blktap
user-space tools and the corresponding kernel module.
After you have successfully installed blktap, do the following to attack the
source image (*/tmp/Centos-6.2-x86_64-minimal-dist.vhd*) to a block device:
Allocate a minor number in the kernel:
.. code-block:: console
# tap-ctl allocate
/dev/xen/blktap-2/tapdev0
Then, spawn a tapdisk process:
.. code-block:: console
# tap-ctl spawn
tapdisk spawned with pid 14879
Now, attach them together:
.. code-block:: console
# tap-ctl attach -m 0 -p 14879
And finally, open the VHD image:
.. code-block:: console
# tap-clt open -m 0 -p 14879 -a vhd:/tmp/Centos-6.2-x86_64-minimal-dist.vhd
Now you can open the associated block device with *snf-image-creator* like
this:
.. code-block:: console
# snf-image-creator /dev/xen/blktap-2/tapdev
When done, you may release the allocated resources by giving the following
commands:
.. code-block:: console
# tap-ctl close -m 0 -p 14879
# tap-ctl detach -m 0 -p 14879
# tap-ctl free -m 0
Limitations
===========
......@@ -331,7 +431,7 @@ Logical Volumes
---------------
The program cannot work on input media that contain LVM partitions inside
[#f1]_. The input media may only contain primary or logical partitions.
[#f2]_. The input media may only contain primary or logical partitions.
Para-virtualized drivers
------------------------
......@@ -347,7 +447,7 @@ ramdisk, otherwise the VM won't be able to boot.
Many popular Linux distributions, like Ubuntu and Debian, will automatically
create a generic initial ramdisk file that contains many different modules,
including the VirtIO drivers. Others that target more experienced users, like
Slackware, won't do that [#f2]_. *snf-image-creator* cannot resolve this kind
Slackware, won't do that [#f3]_. *snf-image-creator* cannot resolve this kind
of problems and it's left to the user to do so. Please refer to your
distribution's documentation for more information on this. You can always check
if a system can boot with para-virtualized disk controller by launching it with
......@@ -399,5 +499,6 @@ supported by both *snf-image-creator* and *snf-mkimage*.
.. rubric:: Footnotes
.. [#f1] http://sourceware.org/lvm2/
.. [#f2] http://mirrors.slackware.com/slackware/slackware-14.0/README.initrd
.. [#f1] http://technet.microsoft.com/en-us/library/bb676673.aspx
.. [#f2] http://sourceware.org/lvm2/
.. [#f3] http://mirrors.slackware.com/slackware/slackware-14.0/README.initrd
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment