Convert usages of nerdctl and crt to crictl

[VannTen]

What would you like to be added

We currently use (AFAICT):

• ctr
• crictl
• nerdctl

If possible, we should use only one CRI frontend for manipulating images and containers.

Why is this needed

1. Avoiding complexity in the playbooks and roles (usage of "command variables" such as crictl_image_pull_command, etc)
2. Reducing the number of tasks, download and config steps.

Not sure what the pros and cons of each are. ctr looks more minimal, maybe that's enough for what we need to do in Kubespray ?
wdyt @yankay @mzaian @floryut @MrFreezeex ?

EDIT: We'll use crictl as it's required by kubeadm, and compatible with all container runtime.

Usage sites can be converted by small batch, then once the conversion is done we'll be able to remove the download of nerdctl and ctr.

[mzaian]

As far as I know crictl is compatible with all the container runtimes. So I would go for it.

[VannTen]

Yeah and I just saw it's required by kubeadm anyway, so that's the obvious candidate

[ant31]

Yes!

Could it be a breaking change during next upgrade for some users?

[VannTen]

That would not be breaking per se (meaning it would not break kubespray itself regardless of inventories, since we would get the cri frontend chosen regardless of what was there before), but if users rely on one of the three specifically, it won't be updated.

[VannTen]

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[yankay]

There are significant documents to describe the difference between nerdctl and crictl. :https://www.slideshare.net/AkihiroSuda/container-plumbing-days-2023-why-was-nerdctl-made

For kubespray, using the crictl_image_pull_command as default is a good idea. It can share the same"pull image" codebase with Kubernetes .👍

As notice:

1: If the var setting is:

download_container: true
download_localhost: true

The image_pull_command_on_localhost will run in the machine "ansible localhost"; the machine may not have crictl installed.

2. The registry mirror config of nerdctl and crictl is different.

[KubeKyrie]

Could I try to work on this?
/assign

[VannTen]

Go ahead !