Connecting from Container to host¶

One problem I faced was to connect to the host from a container. (It was because of a live logging application)

I achieved the desired result by doing adding the extra_hosts section in my compose file:

services:
	example:
	...
		extra_hosts:
		  - logserver.local: host-gateway

With this I can call logserver.local inside of my container and it gets routed to the localhost.

If you want to configure it so that host-gateway points to a specific IP address you can configure it in the /etc/docker/daemon.json

{ "host-gateway-ip": "<desiredIP>" }

This can be especially useful if you install docker without docker-desktop on WSL. Then you can route your host-gateway to the virtual network-interface connecting to windows.

Synchronizing Timezone of Host with Container¶

Docker containers are by default in the timezone ETC/UTC, if you need to have it synchronized to the local machine then you will find multiple options on the internet:

1. Set the TZ variable¶

In a docker-compose.yml:

services:
# ...
# Container Definition in docker.compose.yaml
  environments:
    - TZ=Europe/Berlin

As single command:

docker run -rm -e TZ=Europe/Berlin debian:latest date

2. Bind the system time files to the container¶

In a docker-compose.yml

services:
# ...
# Container Definition in docker.compose.yaml
  volumes:
    - /etc/timezone:/etc/timezone:ro
    - /etc/localtime:/etc/localtime:ro

ENTRYPOINT ["/bin/bash", "startupScript.sh"]

In the script we set the TZ and then startup the application:

#!/bin/bash  
if timezone=$(cat /etc/timezone 2>/dev/null); then  
    export TZ="$timezone"  
    echo "Using Timezone $timezone"  
fi  
./Application # this is the command to run your application

If we do it like this, then every time we restart the container the timezone is synchronized with the host.