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manual: Fix QEMU_NET_OPTS VM-side address.

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In my earlier commit

    manual: Don't suggest exposing VM port to local network.

I made a side change titled

    Use `127.0.0.1` also on the VM side, otherwise connections to
    services that, in the VM, bind to `127.0.0.1` only
    (doing the safe approach) do not work.

Unfortunately, that was wrong:

QEMU inside the VM always communicates via the virtualised
Ethernet interface, not via the VM's loopback interface.
So trying to connect to `127.0.0.1` on the VM's side cannot work.
This commit is contained in:
Niklas Hambüchen 2023-11-11 01:22:13 +01:00 committed by Jörg Thalheim
parent 73b4398b58
commit f9611764c6
2 changed files with 12 additions and 2 deletions
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7
nixos/doc/manual/development/running-nixos-tests-interactively.section.md
View File

@ -62,7 +62,7 @@ where socat is running.
If your test has only a single VM, you may use e.g.
```ShellSession
$ QEMU_NET_OPTS="hostfwd=tcp:127.0.0.1:2222-127.0.0.1:22" ./result/bin/nixos-test-driver
$ QEMU_NET_OPTS="hostfwd=tcp:127.0.0.1:2222-:22" ./result/bin/nixos-test-driver
```
to port-forward a port in the VM (here `22`) to the host machine (here port `2222`).
@ -73,6 +73,11 @@ since a single port on the host cannot forward to multiple VMs.
If the test defines multiple machines, you may opt to _temporarily_ set
`virtualisation.forwardPorts` in the test definition for debugging.
Such port forwardings connect via the VM's virtual network interface.
Thus they cannot connect to ports that are only bound to the VM's
loopback interface (`127.0.0.1`), and the VM's NixOS firewall
must be configured to allow these connections.
## Reuse VM state {#sec-nixos-test-reuse-vm-state}
You can re-use the VM states coming from a previous run by setting the

7
nixos/doc/manual/installation/changing-config.chapter.md
View File

@ -89,7 +89,7 @@ guest. For instance, the following will forward host port 2222 to guest
port 22 (SSH):
```ShellSession
$ QEMU_NET_OPTS="hostfwd=tcp:127.0.0.1:2222-127.0.0.1:22" ./result/bin/run-*-vm
$ QEMU_NET_OPTS="hostfwd=tcp:127.0.0.1:2222-:22" ./result/bin/run-*-vm
```
allowing you to log in via SSH (assuming you have set the appropriate
@ -98,3 +98,8 @@ passwords or SSH authorized keys):
```ShellSession
$ ssh -p 2222 localhost
```
Such port forwardings connect via the VM's virtual network interface.
Thus they cannot connect to ports that are only bound to the VM's
loopback interface (`127.0.0.1`), and the VM's NixOS firewall
must be configured to allow these connections.