Add feature to keep mounts with plain mode

[afbjorklund]

Allows using e.g. virtiofs in plain mode, without needing the guestagent etc.

But only for default mount type, since "reverse-sshfs" still needs non-plain.

Closes #3747

Discussion #3734

[AkihiroSuda]

I fear the explosion of plainFoo, plainBar, plainFooBar properties.

Can we rather introduce guestAgent.enabled: false that will just disable the guest agent without affecting mounts

[afbjorklund]

The ask was only to be able to do virtiofs mounts with vz, without the guestagent (which is doable with this)

[afbjorklund]

But currently this is not related to the guestagent at all, just that enabling Plain will wipe out the Mounts

[AkihiroSuda]

https://github.com/lima-vm/lima/pull/3748/files#r2215365708

[afbjorklund]

The flag could also be different. Perhaps related to mount?

      --mount-none          [limactl create] Remove all mounts
      --mount-keep          [limactl create] Keep mounts in plain mode

Or keep them by default, and require --plain --mount-none

Some templates (like k8s) do an explicit mounts: [] up front...

[msimkunas]

How about --plain --with-mounts?

One other alternative is to replace --plain and allow the user to disable specific features, e.g. --disable-mounts, --disable-port-forwarding, etc. but that would probably be too disruptive.

Or, you could support multiple --disable-* flags and keep --plain as a metaflag that applies all --disable-* flags but this is getting pretty complicated.

[msimkunas]

In any case, users may want to use --plain but enable port forwarding or just mounting. If you anticipate that in the future more exemption flags may be needed (not just --with-mounts) perhaps it is better to think about dedicated flags and treat --plain as an alias/metaflag that applies multiple flags at once

[afbjorklund]

Having both --mounts (string) and --with-mounts (bool) is a little vague, and would --with-mounts=false be the same as --mount-none? Hmm

[afbjorklund]

treat --plain as an alias/metaflag that applies multiple flags at once

We could convert plain from a boolean to a struct, like we did with disk, but I hoped that it wouldn't be needed (complicates the yaml parsing and schema)

• Allow leaving additional disks unformatted #1516

[msimkunas]

@afbjorklund hence my other suggestion to introduce --disable-* flags for disabling specific features. --plain could then just be an alias for multiple such commands, e.g. --disable-mounts --disable-port-forwarding ...

[afbjorklund]

All the other options do require the guestagent, though. Maybe not the timezone, but.

There is also another setting, "copy the user account", that is currently always enabled.

• Describe the different major modes of Lima operation #3749 (comment)

But this got a bit complicated, it was only about the Mounts specifically

---

func fixUpForPlainMode(y *LimaYAML) {
        if !*y.Plain {
                return
        }
        y.Mounts = nil
        y.PortForwards = nil
        y.Containerd.System = ptr.Of(false)
        y.Containerd.User = ptr.Of(false)
        y.Rosetta.BinFmt = ptr.Of(false)
        y.Rosetta.Enabled = ptr.Of(false)
        y.TimeZone = ptr.Of("")
}

[AkihiroSuda]

--disable-<FEAT> is inconsistent with the existing --FEAT=(true|false) flags.

So my suggestion is to introduce --guestagent=(true|false) (default: false) if we want a CLI flag.
Maybe it should rather be set via the YQ syntax (--set '.guestagent.enabled=false').

[afbjorklund]

I think we changed a bit away from "plain", and over to specific flags for the guestagent?

And we didn't quite explain what the guestagent is in the first place, or when you need it