Hypervisors
Each instance runs under a hypervisor: the virtual machine monitor that runs
its guest. Dicer carries two, built into dicerd:
- Cloud Hypervisor, the default.
- Firecracker, with
--hypervisor-type firecracker.
Both run the same images and kernels, and support everything Dicer does with an instance, pausing and snapshots included.
Versions
A daemon carries more than one version of a hypervisor, so that a new one can
be tried without giving up the old. dicer info lists them:
$ dicer info
Hypervisors: cloud-hypervisor v49.0.0 (default), v48.0.0
firecracker v1.17.0
An instance runs the newest version of its hypervisor unless it names one
with --hypervisor-version. A snapshot can only be
restored by the version that took it.
Differences
| Cloud Hypervisor | Firecracker | |
|---|---|---|
| Kernel command line | console=ttyS0 reboot=k panic=1 | the same, and pci=off |
| Ending a guest | powers off | resets, as it has no power button |
How a guest ends is dicer-init’s business, so the difference does not show:
an instance ends the same way under either.