Image Format¶

The image format is a required OS Provider parameter and snf-image will complain if not found
Right now we support 3 different types of image formats:

• extdump
• ntfsdump
• diskdump

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)

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.

diskdump¶

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

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 starting sectors of partitions

Although diskdump is a lot more flexible than 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

Image Properties¶

In order for snf-image to be able to properly configure an image of diskdump format, it needs to be passed a set of image properties:

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

• ROOT_PARTITION={1,2,3,4}
  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, whose password will be reset by snf-image.

All image properties are passed to snf-image through the img_properties OS parameter. The img_properties parameter is mandatory when trying to deploy an image of diskdump format. img_properties should be a json file dumped as a string. When trying to deploy an image of type {ext,ntfs}dump then img_properties are not necessary.