IPA: Spawning container fails with "execv() failed"

[Jacob McCann]

When building my own IPA from https://github.com/openstack/ironic-python-agent the agent does not seem to start. Configuring my IPA to allow me to login I found the following:

-- Unit ironic-python-agent.service has begun starting up.
Jun 30 13:21:17 host-192-168-50-113 systemd-nspawn[638]: Spawning container ironic_python_agent on /opt/ironic-python-agent.
Jun 30 13:21:17 host-192-168-50-113 systemd-nspawn[638]: Press ^] three times within 1s to kill container.
Jun 30 13:21:17 host-192-168-50-113 systemd-nspawn[638]: execv() failed: No such file or directory
Jun 30 13:21:17 host-192-168-50-113 systemd-nspawn[638]: Container ironic_python_agent failed with error code 1.
Jun 30 13:21:17 host-192-168-50-113 systemd[1]: ironic-python-agent.service: main process exited, code=exited, status=1/FAILURE
Jun 30 13:21:17 host-192-168-50-113 systemd[1]: Unit ironic-python-agent.service entered failed state.
Jun 30 13:21:17 host-192-168-50-113 systemd[1]: ironic-python-agent.service failed.

I then tried to do it manually and got the same error. I then started the container without running /usr/local/bin/ironic-python-agent to have a prompt inside the container. If I then run /usr/local/bin/ironic-python-agent while in the container I get:

host-192-168-50-113 ~ # /usr/bin/systemd-nspawn -D /opt/ironic-python-agent \
> --share-system \
> --capability=all \
> --machine=ironic_python_agent \
> --bind=/dev:/dev \
> --bind=/dev/pts:/dev/pts \
> --bind=/proc:/proc \
> --bind=/sys:/sys \
> --bind=/usr/share/oem:/mnt \
> --user=root \
> --keep-unit
Spawning container ironic_python_agent on /opt/ironic-python-agent.
Press ^] three times within 1s to kill container.
root@host-192-168-50-113:~# /usr/local/bin/ironic-python-agent
-bash: /usr/local/bin/ironic-python-agent: /usr/bin/python: bad interpreter: No such file or directory
root@host-192-168-50-113:~# ls /usr/bin/pyth*
/usr/bin/python2.7
root@host-192-168-50-113:~#

It seems /usr/bin/python is missing. A workaround is to comment out the last 'cleanup' section in the Dockerfile (https://github.com/openstack/ironic-python-agent/blob/master/Dockerfile#L28-L31) and create the IPA again. Then everything seems to start and work normally.