Allow for ad-hoc labels when (re)registering

[agracey]

There used to be a way to add a --label flag when running elemental register

This was very useful for when we needed to build cluster based on information about where a system is booted that isn't possible to know at image build time (or system build time).

[kkaempf]

@agracey can you give an example of what kind of information this is ?

[oleg-vorobiov-suse]

Hi Klaus, the one that was dropped in this commit, @kkaempf
5da3ac1

[fgiudici]

Hi Klaus, the one that was dropped in this commit, @kkaempf 5da3ac1

Adding a bit of context there: that commit belongs to Elemental Operator v0.6.0 and follows the first release of the label templating happened just in the previous release, Elemental Operator v0.5.0.
The v0.x release series contains core development and rework of the Elemental Operator: in particular we needed to centralize the management of the labels with the template labels as having clients pushing labels to the operator in an uncontrolled way was not acceptable.

[chargio]

Misuse of labels is a potential way of create malicious nodes that join legitimate clusters, specifically because the specialists managing the upstream cluster is likely not being the same that is managing the node.
We need to design this feature as a Feature Request, and investigate the limits that should be enforced for something like this.

If there are more detailed descriptions of the use cases, we can incorporate them into our research for the topic.

[fgiudici]

Removed the regression label: this was something that was available during the development of the very first supported version of the operator, where a centralized labelling (SMBIOS/ HW labels and later "label templates" feature) was not implemented yet.

[agracey]

The root requirement that we've run into several times is that a system will likely need to dynamically discover which environment it is being booted in.

This discovery process may (and will) be different for each customer based on how they set up their network. More importantly, this needs to be done before the machine is added to a cluster because the information on what cluster is joined or created depends on the result of the some discovery. Due to this, we need a way to add labels or annotations ad-hoc for the MachineInventorySelectorTemplate to select on