How to share files between the host and guests of a NixOS test

[Bas van Dijk]

I'm debugging a NixOS test and I would like to transfer some files from the qemu guests to the host.

I see the guests have a 9p filesystem mounted on /tmp/shared. Is that available from the host?

Alternatively I thought of mounting the root file system of the VM using guestmount from libguestfs. The NixOS manual mentions[1] that when you run the VMs using ./result/bin/nixos-run-vms the root file system of the VMs is created on the fly and kept across VM restarts in ./hostname.qcow2. However I don't see the .qcow2 files in my working directory when I run that command. Where are they created?

Bas

[1] https://nixos.org/nixos/manual/index.html#sec-running-nixos-tests

[Leo Gaspard]

According to the file in `result/bin/run-*-vm` after a `nixos-rebuild
build-vm`, `/tmp/shared` in the guest seems to be equivalent in the host
to the file in `$SHARED_DIR` or, if this variable is not defined, in
`/tmp/nix-vm.*/xchg`

HTH,
Leo

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[Bas van Dijk]

Thanks Leo, I see that /tmp/xchg in the guest is equivalent to /tmp/vm-state-$name/xchg on the host. That solves my problem.

On 5 September 2017 at 19:11, Leo Gaspard <l...@gaspard.io> wrote:

According to the file in `result/bin/run-*-vm` after a `nixos-rebuild
build-vm`, `/tmp/shared` in the guest seems to be equivalent in the host
to the file in `$SHARED_DIR` or, if this variable is not defined, in
`/tmp/nix-vm.*/xchg`

HTH,
Leo

On 09/05/2017 05:38 PM, Bas van Dijk wrote:
> I'm debugging a NixOS test and I would like to transfer some files from
> the qemu guests to the host.
>
> I see the guests have a 9p filesystem mounted on /tmp/shared. Is that
> available from the host?
>
> Alternatively I thought of mounting the root file system of the VM using
> guestmount from libguestfs. The NixOS manual mentions[1] that when you
> run the VMs using ./result/bin/nixos-run-vms the root file system of the
> VMs is created on the fly and kept across VM restarts in
> ./hostname.qcow2. However I don't see the .qcow2 files in my working
> directory when I run that command. Where are they created?
>
> Bas
>
> [1] https://nixos.org/nixos/manual/index.html#sec-running-nixos-tests
>

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