Cant find file shared with `copy_from_vm` in nixos tests

teto · April 6, 2021, 8:00am

Hi,

I am writing a nixos test for a module and incidently the files generated by the test triggers a bug in wireshark.
I would like to export the file to the host to be able to analyze it more comfortably.
I’ve noticed the copy_from_vm feature in the python test driver and tried it in my test but I was not able to find the exported file on the host.
I’ve thus tried with
nix-build -A nixosTests.systemd-analyze which makes use of the feature

github.com

NixOS/nixpkgs/blob/5d6622fce64037e4e80ab00cd2f93d19936bf28f/nixos/tests/systemd-analyze.nix#L44


      
              with subtest("Print statistics"):
                  run_systemd_analyze(["blame"], "blame.txt")
                  run_systemd_analyze(["critical-chain"], "critical-chain.txt")
                  run_systemd_analyze(["dot"], "dependencies.dot")
                  run_systemd_analyze(["plot"], "systemd-analyze.svg")
          
          
    # We copy the main graph into the $out (toplevel), and we also copy
              # the entire output directory with additional data
              with subtest("Copying the resulting data into $out"):
                  machine.copy_from_vm("systemd-analyze/", "")
                  machine.copy_from_vm("systemd-analyze/systemd-analyze.svg", "")
            '';
          })

I’ve then searched for the result fd -Luuu systemd-analyze.svg /tmp to no avail.
the sharing feature relies on virtfs (look at qemu-vm.nix -virtfs local,path=$TMPDIR/xchg,security_model=none,mount_tag=xchg \) so I wonder if this could come from my kernel config, a standard one. lsmod|grep 9p or lsmod|grep virt are empty, could that be it ?