Images

Every disk image on this engine: the ones VMs boot from, the master images stacks are built from, and any ISO used as a CD-ROM.

An image in use says which VM has it; an unused one can be attached, cloned, converted or deleted. The usage column shows how much of an image's virtual size has actually been written - a qcow2 image only takes up what it holds.

Add image

Three ways to get an image onto the engine: an empty disk to install onto, a file uploaded from this computer, or a file the engine fetches from a URL. A download carries on whether or not this page stays open.

Name

What the image is called. The file it is stored in is named after it, so two images cannot share a name in the same storage pool.

Size

How large the disk appears to the guest. A qcow2 or VMDK image only takes up the space actually written to it, so this is the ceiling rather than the cost, and it cannot be lowered afterwards.

Format

QCOW2 grows as it is written and can be snapshotted; raw is a plain disk image, fastest and fixed size; VMDK is for moving an image to VMware.

Image file

A disk image or CD-ROM to upload: .qcow2, .img, .iso, .vmdk, .vdi, .vhd or .vhdx. It keeps the file's own name, and the upload can be cancelled while it runs.

URL

An address the engine fetches the image from itself. The transfer happens on the engine, so this page can be closed - the image shows up as downloading until it is here.

Storage pool

Which storage the image is kept on. Shared pools let a VM move between nodes; node storage is faster and ties the VM to the node it is on.

Cloning an image

Copies an image, so the copy can be attached to another VM. Cloning a master image is how a VM gets its own disk from a shared starting point.

Snapshots

A snapshot is the state of an image at a moment, kept inside the image itself. Reverting throws away everything written since. Snapshots cost space and slow an image down as they pile up.

Master images

A master image is one that other images are cloned from, and is what a stack is built around. Making an image a master fixes it: it is no longer written to, only copied.

Backups

A backup is a copy of an image held apart from it, taken on the schedule the image carries. Restoring puts an old copy back in place of the current one.

While an image on the engine's storage is backed up, the Images tab shows how far the backup has got.

An image in use by a running VM can only be backed up while the VM runs if it is on LVM storage, which can be snapshotted. Elsewhere, Backup offers to pause the VM while the image is backed up and to resume it afterwards; paused, the VM keeps its memory and carries on where it left off. The backup itself does the pausing and the resuming - on the engine, or on the node for an image on a node's own storage - so it finishes the same whatever happens to the page or to Keal. While it is paused, its monitors that are on are paused too - shown as paused for a backup, the time counting neither for nor against them - and switched back on when it is resumed. From the command line: keal images backup NAME --pause.

Links

Where what runs from an image is managed, reached and kept up to date. A VM built from the image takes them from it, and so does a stack managed through that VM.

In each, {uuid} stands for the VM's network, {externalip} for its external address and {internalip} for its internal one; they are filled in for each VM. An image cloned from a master starts out with the master's links. Clearing one takes it away from every VM running from this image.