Image Format

Version 6 (Nikos Skalkotos, 11/23/2011 04:51 pm) → Version 7/39 (Nikos Skalkotos, 11/23/2011 05:00 pm)

h1. Image Format

Right now we support 4 different types of images:
* extdump
* ntfsdump
* diskdump
* custom

h2. extdump & ntfsdump

Those two formats are raw copies (using dd) of partitions hosting Linux systems on ext{2,3,4} and Windows systems on ntfs filesystems respectively.

Partitions hosting a Windows or Linux system that are suitable for dumping should have the following properties:
* Be the first partition in the filesystem
* The OS they host should not depend on any other partitions
* Start at sector 2048
* Have a bootloader installed in the partition
* Have the root device in /etc/fstab specified in a persistent way, using UUID or LABEL (for extdump only)

h3. Known Issues

* For linux systems, having grub installed in the partition is fragile and things can go wrong when resizing the partitions, especially when shrinking.
* Swap space is not supported.
* More complicated partition schemes are not supported.

h2. diskdump

Diskdump is a newer format that overcomes most of the aforementioned issues. This format is a raw copy (dd) of a whole disk. disk, instead of a partition.

This design decision has the following benefits:
* Swap partitions are supported
* The system may use multiple partitions:
** dedicated partitions for /boot, /home etc in linux
** system and boot partition in Windows
* There are no restrictions on partitions starting sectors of partitions

Although diskdump is a lot more flexible that the older formats, there are still some rules to follow:
* All devices in fstab should be specified by persistent names (UUID or LABEL)
* LVMs and extended partitions should be avoided.
** The support for extended partitions is partial. snf-image does not support resizing logical partitions.
** Logical volumes are not supported at all
* In Linux disks only ext{2,3,4} filesystems are supported

h3. Image Properties

In order for snf-image to be able to properly configure a diskdump image it needs to be aware some of image properties:

* *OSFAMILY={linux|windows}*
This specifies whether the image is a Linux or a Windows Image

* *ROOT_PARTITION=[1234]*
This specifies the partition number of the root partition. As mentioned earlier, for now we only support primary partitions

* *USERS="username1 username2...."*
This is a list of users, snf-image should try to reset the password for.