diff --git a/doc/source/user/formats.rst b/doc/source/user/formats.rst index 0e05a3d76a..d7a7ebcd76 100644 --- a/doc/source/user/formats.rst +++ b/doc/source/user/formats.rst @@ -36,51 +36,79 @@ You can set your image's disk format to one of the following: * **raw** - This is an unstructured disk image format + This is an unstructured disk image format. + + The ``raw`` image format is the simplest one, and is natively supported by + both KVM and Xen hypervisors. You can think of a raw image as being the + bit-equivalent of a block device file, created as if somebody had copied, + say, ``/dev/sda`` to a file using the :command:`dd` command. * **vhd** - This is the VHD disk format, a common disk format used by virtual machine - monitors from VMware, Xen, Microsoft, VirtualBox, and others + This is the VHD (Virtual Hard Disk) disk format, a common disk format used by + virtual machine monitors from VMware, Xen, Microsoft, VirtualBox, and others. * **vhdx** - This is the VHDX disk format, an enhanced version of the vhd format which - supports larger disk sizes among other features. + This is the `VHDX + `_ format, an + enhanced version of the ``vhd`` format. It has support for larger disk sizes + and protection against data corruption during power failures. * **vmdk** - Another common disk format supported by many common virtual machine monitors + The + `VMDK `_ + (Virtual Machine Disk) format is supported by many common virtual machine + monitors, for example the VMware ESXi hypervisor. * **vdi** - A disk format supported by VirtualBox virtual machine monitor and the QEMU - emulator + The `VDI `_ + (Virtual Disk Image) format for image files is supported by the VirtualBox + virtual machine monitor and the QEMU emulator. * **iso** - An archive format for the data contents of an optical disc (e.g. CDROM). + The `ISO + `_ + format is a disk image formatted with the read-only ISO 9660 (also known + as ECMA-119) filesystem commonly used for CDs and DVDs. * **ploop** - A disk format supported and used by Virtuozzo to run OS Containers + A disk format supported and used by Virtuozzo to run OS Containers. * **qcow2** - A disk format supported by the QEMU emulator that can expand dynamically and - supports Copy on Write + The `QCOW2 `_ + (QEMU copy-on-write version 2) format is commonly used with the + KVM hypervisor. It uses a sparse representation, so the image size + is smaller than a raw format file of the same virtual disk. It can + expand dynamically and supports Copy on Write. + +The `AKI/AMI/ARI +`_ +format was the initial image format supported by Amazon EC2. +The image consists of three files, each of which has its own specific +``disk_format`` identifier: * **aki** - This indicates what is stored in Glance is an Amazon kernel image + This indicates what is stored in Glance is an Amazon Kernel Image (AKI). + It is a kernel file that the hypervisor will load initially to boot the + image. For a Linux machine, this would be a ``vmlinuz`` file. * **ari** - This indicates what is stored in Glance is an Amazon ramdisk image + This indicates what is stored in Glance is an Amazon Ramdisk Image (ARI). + It is an optional ramdisk file mounted at boot time. + For a Linux machine, this would be an ``initrd`` file. * **ami** - This indicates what is stored in Glance is an Amazon machine image + This indicates what is stored in Glance is an Amazon Machine Image (AMI). + It is a virtual machine image in raw format. Container Format ---------------- @@ -103,32 +131,42 @@ You can set your image's container format to one of the following: * **bare** - This indicates there is no container or metadata envelope for the image + This indicates there is no container or metadata envelope for the image. * **ovf** - This is the OVF container format + `OVF `_ + (Open Virtualization Format) is a packaging format for virtual machines, + defined by the Distributed Management Task Force (DMTF) standards group. + An OVF package contains one or more image files, a ``.ovf`` XML metadata file + that contains information about the virtual machine, and possibly other + files as well. + + An OVF package can be distributed in different ways. For example, + it could be distributed as a set of discrete files, or as a tar archive + file with an ``.ova`` (open virtual appliance/application) extension. * **aki** - This indicates what is stored in Glance is an Amazon kernel image + This indicates what is stored in Glance is an Amazon kernel image. * **ari** - This indicates what is stored in Glance is an Amazon ramdisk image + This indicates what is stored in Glance is an Amazon ramdisk image. * **ami** - This indicates what is stored in Glance is an Amazon machine image + This indicates what is stored in Glance is an Amazon machine image. * **ova** - This indicates what is stored in Glance is an OVA tar archive file + This indicates what is stored in Glance is an OVA tar archive file, + that is, an OVF package contained in a single tar archive file. * **docker** This indicates what is stored in Glance is a Docker tar archive of - the container filesystem + the container filesystem. * **compressed**