zlacker

>>jakels+(OP)
> I also enabled UFW (which I should have done ages ago)

I disrecommend UFW.

firewalld is a much better pick in current year and will not grow unmaintainable the way UFW rules can.

    firewall-cmd --persistent --set-default-zone=block
    firewall-cmd --persistent --zone=block --add-service=ssh
    firewall-cmd --persistent --zone=block --add-service=https
    firewall-cmd --persistent --zone=block --add-port=80/tcp
    firewall-cmd --reload

Configuration is backed by xml files in /etc/firewalld and /usr/lib/firewalld instead of the brittle pile of sticks that is the ufw rules files. Use the nftables backend unless you have your own reasons for needing legacy iptables.

Specifically for docker it is a very common gotcha that the container runtime can and will bypass firewall rules and open ports anyway. Depending on your configuration, those firewall rules in OP may not actually do anything to prevent docker from opening incoming ports.

Newer versions of firewalld gives an easy way to configure this via StrictForwardPorts=yes in /etc/firewalld/firewalld.conf.

>>3np+pm
If you can, do not expose ports like this 8080:8080, but do this "192.168.0.1:8080:8080" so its bound to a private IP. Then use any old method expose only what you want to the world.

In my own use I have 10.0.10.11 on the vm that I host docker stuff. It doesn't even have its own public IP meaning I could actually expose to 0.0.0.0 if I wanted to but things might change in the future so it's a precaution. That IP is only accessible via wireguard and by the other machines that share the same subnet so reverse proxying with caddy on a public IP is super easy.

>>dizhn+u41
It's really a trap. I'm surprised they never changed the default to 127.0.0.1 instead of 0.0.0.0. So you would need to explicitly specify it, if you want to bind to all interfaces.

>>andix+2r1
The reason is convenience. There would be a lot more friction if they didn't do it like this for everything other than local development.

Docker also has more traps and not quite as obvious as this. For example, it can change the private IP block its using without telling you. I got hit by this once due to a clash with a private block I was using for some other purpose. There's a way to fix it in the config but it won't affect already created containers.

By the way. While we're here. A public service announcement. You probably do NOT need the userland-proxy and can disable it.

/etc/docker/daemon.json

{ "userland-proxy": false }

>>dizhn+oy1
Is there a guide that lists some common options / gotchas in Docker like this?

Some quick searching yields generic advice about keeping everything updated or running in rootless mode.