v1.0 roadmap: change the default mount driver from reverse-sshfs to 9p (for QEMU) and virtiofs (for vz)

[AkihiroSuda]

https://github.com/lima-vm/lima/blob/master/docs/mount.md

Lima v1.0 will change the default mount driver from reverse-sshfs to 9p for QEMU, virtiofs for vz. (The default vm driver will be vz)
RHEL-like templates will continue to use reverse-sshfs as their kernel lacks support for virtio-9p-pci.

[afbjorklund]

Did changing the sftp server fix the odd bugs, like when you can't compile any code (due to umask) ?

• Support using OpenSSH sftp server instead of using github.com/pkg/sftp sshocker#17

• Compiling go code, inside host mounted folder prevent the binary file being executable #602

Support for virtfs is also lacking on Windows and other host OS (like BSD), requires Linux or macOS

[AkihiroSuda]

QEMU 7.1 is released and seems to have resolved issues like:

• "Network dropped connection on reset" errors on 9p mounts #831

@jandubois @afbjorklund Are we ready to change the driver (on Linux and macOS) and release v1.0 soon?

[afbjorklund]

According to one user*, there might be 9p support also on Windows hosts soon: (haven't tried it myself, not included in 7.1.0)

* #909 (comment)

As far as I know, there should be no major issues with virtfs on Linux (if reverse-sshfs is still available as a fallback, that is) ?

[AkihiroSuda]

Before changing the default driver probably we should add a simple CLI flag like limactl start --mount-type=reverse-sshfs to allow switching back to the reverse-sshfs driver. (Colima already has a similar flag)

The --mount-type=... flag value will be stored in the "local" override.yaml stored in the instance dir so as not to break comment lines and white spaces in the main lima.yaml.
The "global" override.yaml in the _config dir will still have higher precedence.
I'll work on this after getting #1069 merged.

(Instead of messing up the overriding system we could just modify lima.yaml, but modifying YAMLs without breaking comments lines and white spaces turned out to be hard: https://github.com/AkihiroSuda/yamlctl)

cc @jandubois

[dnrce]

Per #454 (reply in thread), will a writable ~ mount also become the default as part of this change?