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

[jandubois]

So assuming we enabled mounts (except for reverse-sshfs) for --plain mode in Lima 2.0. Wouldn't --plain --mount-none already work?

So I'm not sure I see a need for additional options.

[AkihiroSuda]

That's a breaking change and also inconsistent across mount types.
Sshfs does not work with the plain mode.
IIUC even virtiofs doesn't work on some distro in the plain mode as the relevant kmod is not installed by default. (Lazy to confirm it from phone 😅 )

[msimkunas]

That's a breaking change and also inconsistent across mount types.
Sshfs does not work with the plain mode.
IIUC even virtiofs doesn't work on some distro in the plain mode as the relevant kmod is not installed by default. (Lazy to confirm it from phone 😅 )

@AkihiroSuda Perhaps the bigger issue is that currently there's no way to specify which boot scripts must be run. In my case, I only need virtiofs support in the VM and nothing else, but currently I can either run all boot scripts or none.

I could perhaps solve this by copying the boot script which sets up the virtiofs mount and using it as a provisioning script though...

[jandubois]

Perhaps the bigger issue is that currently there's no way to specify which boot scripts must be run. In my case, I only need virtiofs support in the VM and nothing else, but currently I can either run all boot scripts or none.

The boot scripts are not an external facing API. We need to be able to modify them in incompatible ways on any release, without having to provide backwards compatibility.

Any configurability comes from settings in lima.yaml.

I could perhaps solve this by copying the boot script which sets up the virtiofs mount and using it as a provisioning script though...

If we decide to make mounts available under --plain, then I think we should run the required boot scripts to install the needed drivers, but only if the list of mount points is non-empty.

So if somebody runs a VM with --plain and doesn't provide any mounts, they won't get any drivers installed.

[afbjorklund]

Will close this PR, until we know how the config for plain mode should be handled. But it's basically a oneliner.

--- a/pkg/limayaml/defaults.go
+++ b/pkg/limayaml/defaults.go
@@ -871,7 +871,6 @@ 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)