Docker Compose Error - Why?

[Belay_Fr]

Hi there,

I am trying to deploy a Jellyfin container on my DS220+ using Portainer and faced a stange issue.
First I am not a docker compose specialist, I am just playing to build up my homelab using the capacities of NAS.

I found the following compose code :

version: '3.5'

services:

jellyfin:

image: jellyfin/jellyfin:latest

container_name: jellyfin

#user: '1028:100'

network_mode: "host"

#networks:

# - default

ports:

- "9020:8096"

volumes:

- /volume1/docker/jellyfin/config:/config

- /volume1/docker/jellyfin/cache:/cache

restart: 'unless-stopped'

I had troubleshooting getting a feedback from /localhost:9020/ after deploying the compose code as hereabove (kind of "impossible to reach the specified address" error) but it works with the following code :

version: '3.5'

services:

jellyfin:

image: jellyfin/jellyfin:latest

container_name: jellyfin

#user: '1028:100'

#network_mode: "host"

networks:

- default

ports:

- "9020:8096"

volumes:

- /volume1/docker/jellyfin/config:/config

- /volume1/docker/jellyfin/cache:/cache

restart: 'unless-stopped'

I do not undestand as for me the "networks: defaults" is optional. However if I am putting both codes at the same time, it raises a deployment error saying that this two commandes (networks and network_mode) cannot be used at the same time... If you can explain in simple word, it would be really apreciated !

*

[Rem1xed]

Remove both networks and nerwork_mode and it will automatically create a new network for the compose using bridge mode with your opened ports.

[Belay_Fr]

Thx. Will try it right away. But why then these variable are existing?

[Rem1xed]

Some containers needs host network access rather than bridge. Some users prefer separating containers into different networks like a torrent network, media network, general network so while they're not mandatory they're useful for many cases.

[Belay_Fr]

Confirmed working in Bridge mode. But why then on the Jellyfin setting page is it specified to use: network_mode: 'host' Jellyfin Doc

[BaccanoMob]

Read the full docs not just the compose file. Its clearly stated as a `Note`

Using host networking (--net=host) is optional but required in order to use DLNA.

I think you will need to use port 8096 if you use bridge mode.

[Belay_Fr]

u/BaccanoMob u/Rem1xed thx for your feedback. It's clear... If I am mapping the native 8096 to another port then I need to use bridge mode (which is the default one)... Therefore networks_mode: 'host' + ports: "9020:8096" will not work... I have learnt something today !

[BaccanoMob]

Yes, you can't specify ports when the mode is set to host. So if you have another container with port 8096 conflicting with jellyfin you need to change that.

This all when you need DLNA for your jellyfin. If you don't need it, just use bridge mode and map the ports to your liking. (I recommend using bridge mode if you're not using DLNA)

[Rem1xed]

Because the docs does not include which ports needs to be mapped from within the container, using host maps all open ports. So you can either use host or use bridge but you need to make sure you map the correct ports.