Best way to transfer files in and out of a mkosi qemu VM?

[gabevenberg]

Ordinarily id use SCP or, if I need to mount something, virtiofsd. However, qemu wraps ssh itself, and I'm not extremely clear as to if there is a clean way to get mkosi to setup virtiofsd. For full clarity, my usecase is that im using a cross-arch qemu emulated image to compile an application for armv7 on an x86 host, with a tool that does not itself support cross-compilation. Eventually, I want this to be part of our CI. What would be the best way to programmatically transfer the source code in to, and then the build artifacts out of, the VM?

[daandemeyer]

See the RuntimeBuildSources= and RuntimeTrees= options

[gabevenberg]

Im blind, thanks for pointing that out. Is there an easy way to scp files in and out, or is mounting the only option?

[daandemeyer]

It's probably possible, but I've never tried it myself

[theCalcaholic]

Im blind, thanks for pointing that out. Is there an easy way to scp files in and out, or is mounting the only option?

@gabevenberg My current (not ideal) approach is to connect to the vm with mkosi ssh, then check ps aux | grep ssh and copy the ssh command and adapt it to my need :D

Here's an example, how the resulting command looks:

ssh \
  -i /path/to/mkosi.key \
  -F none \
  -o UserKnownHostsFile=/dev/null \
  -o StrictHostKeyChecking=no \
  -o LogLevel=ERROR \
  -o ProxyCommand="socat - VSOCK-CONNECT:375801266:%p" \
  root@mkosi

But I've been planning for some time to investigate how mkosi figures out the vsock id and skip the mkosi ssh step.

EDIT: Turns out, the vsock id is configurable with VSockCID= in mkosi.config!

EDIT2: And if you need a generic way of connecting to mkosi VMs, here's how: mkosi keeps some metadata about the VM in "$XDG_RUNTIME_USER/mkosi/machine/machine-name.json", including everything needed to connect to the VM with ssh (specifically, the required ssh key and proxy command). Here's the script I'm using to do this right now: https://cryptpad.fr/code/#/2/code/view/ttYhB2TQZYrLW-WVpW60rRauDtHoCOvUVhDBWBcTj2A/