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Nikos Skalkotos, 11/24/2011 02:41 pm
Image Format¶
The image format (img_format
) is a required OS Provider parameter and snf-image will complain if not foundRight 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
- 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, it may make use of a set of image properties. Those image properties are passed to snf-image by Ganeti through the img_poroperties
OS parameter. For the diskdump
format some properties are mandatory. For older formats ({ext,ntfs}dump) all image properties are optional.
- Mandatory properties (for
diskdump
only)- OSFAMILY={linux,windows}
This specifies whether the image is a Linux or a Windows Image. {ext,ntfs}dump formats are self descriptive regarding this property. - 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. For {ext,ntfs}dump formats this property is trivial (they host only one partition).
- OSFAMILY={linux,windows}
- Optional properties
- USERS="username1 username2...."
This is a list of users, whose password will be reset by snf-image.
- USERS="username1 username2...."
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.