add local network backup support.

[fotoklaasje]

I use urbackup for local network backups, server and client run in separate dockers on the same machine. At the moment the dockerfile for this docker contains CMD ["--internet-only"], forcing the client into internet mode. This causes unnecessary network traffic to the router and back, congesting my ethernet connection and slowing the backups. i would greatly appreciate it if this flag could be removed or replaced by an environment variable, which I can change.

[jejanim]

I'd appreciate that change too.
The hard-coded, enabled internet mode prevents me from using this image.

[knumsi]

I cannot get it up and running. QNAP TVS-672XT Container Station shows the following log:
2020-09-09 22:49:29: ERROR: urbackupserver: Failed binding ipv6 socket to port 35623. Another instance of this application may alrea be active and bound to this port. 2020-09-09 22:49:29: urbackupserver: Server started up successfully! 2020-09-09 22:49:29: Started UrBackupClient Backend... Backing up volume /backup 2020-09-09 22:49:30: Looking for old Sessions... 2 sessions 2020-09-09 22:49:30: Final path: /backup 2020-09-09 22:49:39: Final path: /backup

Config is:
`version: '3'

services:
urbackup:
image: uroni/urbackup-client:latest
container_name: urbackup-client
environment:
- TZ=Europe/Berlin # Enter your timezone
- URBACKUP_SERVER_NAME=XYZ (Local Lan Name or Internet Name dont change anything)
- URBACKUP_CLIENT_NAME=XXX (Like shown in the status overview)
- URBACKUP_CLIENT_AUTHKEY=XYZABC (as set up in
volumes:
- /share/CACHEDEV1_DATA:/backup:ro
ports:
- 35621:35621
- 35622:35622
- 35623:35623`

Removing the three ports in the config did not solve anything. Both Devices are on the local network.

[knumsi]

Okay - workaround for me after long searching around:
Router ist opnsense:
Add in "Services: Unbound DNS: Overrides" the external host to point at the internal Urbackup IP.

Now it works. with my before mentioned YAML.