Comment 1 for bug 1599886

Thanks for the bug report. The apt-mirror setting seems to copy what setting your desktop's apt mirror does in software sources, which isn't useful in your case.

I think the current supported way to isolate a Juju environment from the internet, but still be able to install packages, is to set up a proxy. This is what I have used in the past (but haven't tried recently):

In clouds.yaml for Juju 2.0. Similar options are available for 1.25.x
clouds:
  maas-proxied:
    type: maas
    auth-types: [oauth1]
    endpoint: http://192.168.1.2/MAAS/
    apt-http-proxy: 192.168.0.2:8000
    apt-https-proxy: 192.168.0.2:8000
    http-proxy: 192.168.0.2:8000
    https-proxy: 192.168.0.2:8000