Improve k0sctl init usefulness by accepting a list of addresses

[kke]

Trying to make k0sctl init a bit more useful and the output actually to be usable as-is when you provide some bits of data.

Addresses can be set via k0sctl init address1 address2 address3 or via stdin: somecommand | k0sctl init.

The addresses can be:

• just an address
• user@address
• address:ssh_port
• user@address:ssh_port

With the parameter --controller-count you can set how many of those hosts are going to be controllers. An alternative would be to use something like --controllers="address1,address2,..." --workers="address3,address4.." but that would then be difficult if stdin is accepted 🤔 .

The keypath, default user and cluster name can be set via flags.

Example:

$ $ go run . init --user admin --cluster-name k0s-r0x --key-path ~/.ssh/id_rsa 10.0.0.1 10.0.0.2:8022 upuntu@10.0.0.3:9022

==>

apiVersion: k0sctl.k0sproject.io/v1beta1
kind: Cluster
metadata:
  name: k0s-r0x
spec:
  hosts:
  - ssh:
      address: 10.0.0.1
      user: admin
      port: 22
      keyPath: /Users/kimmo/.ssh/id_rsa
    role: controller
    os: ""
  - ssh:
      address: 10.0.0.2
      user: admin
      port: 8022
      keyPath: /Users/kimmo/.ssh/id_rsa
    role: worker
    os: ""
  - ssh:
      address: 10.0.0.3
      user: upuntu
      port: 9022
      keyPath: /Users/kimmo/.ssh/id_rsa
    role: worker
    os: ""
  k0s:
    version: 1.21.0+k0s.0

[kke]

Fishing for thoughts at this point, not actual reviews unless you think it's already good as is.

[ncopa]

I like this idea. I think that we don't really need to worry about stdin support if we have the options as k0sctl init [options] [ADDRESS...] since you can use xargs. For example:

sh get-ip-addr-list.sh | xargs k0sctl --user admin --key-path=~/.ssh/id_rsa

which would be equivalent to:

sh get-ip-addr-list.sh > /tmp/list
k0sctl --user admin --key-path=~/.ssh/id_rsa $(cat /tmp/list)

I also prefer the --controller-count=3 style over --controllers=$ip1,$ip2,$ip3