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[Olivier DUCROT]

Extrait du livre de peachpit : Mac OS X Deployment v10.5 page 52
(livre que je te recommande)

Understanding Disk Images
Although you can create disk images of small size and containing only a few
items, every disk image file is a container that simulates the capabilities
of a storage device. You can store multiple partitions and file systems
inside a single disk image, just as you would on a standard hard drive.
Nearly any volume type for which Mac OS X supports read/write capability can
be stored in a disk image file. In general, though, most disk images contain
a single partition that is created as a Mac OS Extended volume.
Mac OS X v10.5 supports the following disk image volume types:
P  Mac OS Standard (HFS) P  Mac OS Extended (HFS+)
P  Mac OS Extended and Journaled (HFS+J)
P  Mac OS Extended, Case Sensitive, and Journaled (HFSX)52 Deploying
Individual Items and Containers
P  Universal File Structure (UFS)
P  MS-DOS (FAT16/32)
You also have a choice of disk image format types when creating or
converting a disk image. The disk image format type defines the data
structure of the disk image file itselfthat is, how the data is saved when
the disk image is created or modified. It does not, however, define the
structure of the contents; no matter what disk image format you choose, the
contents will always appear to Mac OS X as they do on a standard storage
device. 
Mac OS X v10.5 supports the following disk image format types:
P  Read/write disk image‹This is the standard disk image type and is
indicated by the .dmg file extension. This type allows you unlimited read
and write capability to the contents of the disk image. With all read/write
image types, you can create a blank image and add content to it later, or
you can create an image with the contents of a folder or another image,
which you can modify to suit your needs. A read/write disk image file is
saved as a single monolithic file, and its size is set when created.
However, you can change the volume size later using disk image management
tools. 
P  Read/write sparse image‹This is an expandable disk image type and is
indicated by the .sparseimage file extension. This type is also read/write
capable, but the disk image file will automatically size to fit the disk
image contents. Using this type, you still have to define a maximum image
size, but the image file itself will be no larger than what¹s necessary to
store the image contents. Again, the disk image file itself is saved as a
single monolithic file. P  Read/write sparse bundle image‹This is a new
image type with Mac OS X v10.5 and is indicated by the .sparsebundle file
extension. This type is similar to the sparse image, with the disk image
file automatically sized to fit the disk image contents, but the disk image
file is saved as a package containing multiple storage bands. These storage
bands can vary in size up to 128 MB, but the default size is 8 MB. As the
image contents expand, new bands are added to accommodate the increased
capacity. This new disk image format is used in Mac OS X v10.5 for FileVault
encrypted home folders and network Time Machine backups.

NOte P The sparse bundle image format is compatible only with Mac OS X v10.5
and is not recommended for deployment use because it¹s saved as a package.
Packages are not compatible with most third-party file storage and transport
mechanisms.

P Read-only disk image‹This disk image type is similar to the standard
read/write image type except that the image¹s contents are not editable.
This type is also indicated by the .dmg file extension. The only time you
can add to this type of disk image is during its creation by using the
contents of a folder or another disk image; users cannot erase any part of a
read-only image after it is created. Because read-only images are saved as a
single monolithic file, they are a suitable format for deploying items or
entire system drives.
P  Read-only compressed disk image‹This disk image type is similar to the
read-only disk image except that the contents have been compressed. The
algorithm used is very similar to ZIP compression, so you can expect a 50
percent size reduction on average. Compressing a disk image not only halves
the required storage space, it also provides increased performance during
deployment because it effectively doubles available network bandwidth.
Therefore, this image type is ideal for deploying items or entire system
drives. 
P  DVD/CD master image‹This disk image type is primarily used for storing
master copies of optical disc volumes and is indicated by the .cdr file
extension. These images are also read-only and must be created using the
contents of another volume or disk image. This type is unique because it
contains a copy of all sectors of a disk regardless of whether they are
used. This allows you to save and later burn a bit-for-bit copy of the
original media. While this is ideal for duplicating media, it¹s not ideal
for most Mac OS X deployment purposes. On the other hand, this is the only
disk image type that is generally compatible with third-party systems.
P  Hybrid image (HFS+/ISO/UDF)‹The hybrid image type is unique in that it
includes volume information about the disk image contents in three formats:
Mac OS Extended, ISO9660, and Universal Disk Format. Hybrid disk images are
created using the contents of another folder or volume, and and are
therefore read-only. Disk images of this type use the .dmg file extension,
but have the advantage of being readable on most modern third-party systems
because of the inclusion of ISO and UDF volume information. This
compatibility feature makes hybrid disk images an attractive option for
deploying items to third-party systems. However, applying any of the
compression or encryption algorithms used by Mac OS X will likely break
compatibility with thirdparty systems. As a result, you cannot create
compressed hybrid disk images with Disk Utility. Thus, if you¹re deploying
only to Mac OS X systems, you¹re better served by compressed disk images.

le 06/08/09 16:46, Fabien COMBERNOUS à fcombernous at kezia.com a écrit :

> Olivier DUCROT wrote:
>> Non, ce n'est pas spécifique, c'est surtout que le système est ultra light,
>> presque équivalent à celui d'un DVD d'installation Apple, avec un minimum de
>> fonctions !
>>   
> 
> J'ai fait une image minimum mais elle n'a pas le menu en question
> grisée. Et d'ailleur moi avec l'outil System Image Utility me donne un
> fichier dmg. Alors que DeployStudio utilise un .sparseimage.
> Et ce dmg boote mais mais j'ai beau avoir fait un NetInstall avec le
> System Image Utility cette image ne Netboot pas.
> Et mon dmg il fait 7Go alors que le sparse image il fait 1G environs.
> Pourtant quand je regarde le contenu en montant les images il est
> presque identique.
> 
> Je pense que sparseimage a une structure plus simple et/ou compacté que
> dmg. Il doit être possible de passer de dmg à sparseimage.

La théorie, c¹est quand on sait tout mais que rien ne marche
La pratique, c¹est quand tout marche mais qu¹on ne sait pas pas pourquoi
Et l¹informatique, c¹est l¹union de la théorie et de la pratique : rien ne
marche et on sait pas pourquoi

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