Commit 7dfcf976 authored by Nikos Skalkotos's avatar Nikos Skalkotos

docs: Update the "supported images" section

snf-image-creator can work with different image formats nowadays.
parent d1000f25
......@@ -2,8 +2,12 @@ Overview
^^^^^^^^
snf-image-creator is a simple command-line tool for creating OS images. The
original media the image is created from, can be a block device, a regular
file that represents a hard disk or the host system itself.
original media, the image is created from, can be:
* a block device, representing a hard disk
* a disk image file, representing a hard disk (supports all image file formats
supported by QEMU)
* the host system itself
Snapshotting
============
......
......@@ -318,102 +318,17 @@ 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*.
*snf-image-creator* is able to work with the most popular disk image formats.
It has been successfully tested with:
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
* Raw disk images
* VMDK (VMware)
* VHD (Microsoft Hyper-V)
* VDI (VirtualBox)
* qcow2 (QEMU)
It can support any image format QEMU supports as long as it represents a
bootable hard drive.
Limitations
===========
......
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