machine_core: Add Machine nspawn clone API #6974
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So there are several problems with this -- RHEL does not have networkd, and many/most OSes don't have a snapshot-capable file system, e.g. debian-stable. There,
On debian-stable I've had some success with creating overlay delta directories and doing However, |
There are tests which require two independent machines in terms of networking, services, packages, and file systems -- this can cover e.g. the shell's host switching, or cockpit-machine's VM migration or remote terminal functionality. Previously we used destructive tests with `provision`ing multiple VMs; but this is expensive and prevents us from running these tests in tmt. But for the above tests which don't require kernel modules/functionality, we would be quite happy with the auxiliary machines being a container. Use systemd-nspawn to boot its own parent OS/file system with transient overlays. Unfortunately we can't use the convenient `--ephemeral`: that makes a snapshot of the entire fs, which only works efficiently on btrfs. But we can use `--volatile` and set up a bunch of overlays ourselves. Wrap that functionality into a convenient `Machine.clone_container()` API which returns a new Machine (NspawnMachine subclass) with the usual methods. Teach `SSHConnection` about a jump host (using `ProxyCommand`) to directly connect from the outside test to the inner nspawn container. This first version only supports one cloned container at a time. Supporting multiple would be nice, but requires some reengineering of the SSHConnection master.
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Next step -- more legwork with manual overlays, which should work fine on ext4 now. I triggered another round of testing. Remaining big issue is that neither RHEL nor CoreOS have systemd-networkd, which makes configuring the inner and outer veth awkward. Need to find a way to do this with NM or other tools. |
| parent.execute(f"until timeout 1 nc -z {address} 22; do sleep 1; done") | ||
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| address, parent.image, verbose, parent.label + "-" + label, |
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Looks like self.verbose and maybe others should be initialized earlier, in case the code above throws an error.
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FTR: I played around with |
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Some more ideas:
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There are tests which require two independent machines in terms of networking, services, packages, and file systems -- this can cover e.g. the shell's host switching, or cockpit-machine's VM migration or remote terminal functionality.
Previously we used destructive tests with
provisioning multiple VMs; but this is expensive and prevents us from running these tests in tmt. But for the above tests which don't require kernel modules/functionality, we would be quite happy with the auxiliary machines being a container.systemd-nspawn supports booting its own parent OS/file system with a transient overlay. Wrap that functionality into a convenient
Machine.clone_container()API which returns a new Machine (NspawnMachine subclass) with the usual methods. TeachSSHConnectionabout a jump host (usingProxyCommand) to directly connect from the outside test to the inner nspawn container.This first version only supports one cloned container at a time. Supporting multiple would be nice, but requires some reengineering of the SSHConnection master.
I tested this locally, and also sent a Cockpit PR to exercise this: cockpit-project/cockpit#21105