How to find host ip address in dockerfile

Question

I want to use the host ip address in container, how should I achieve this in dockerfile way?

FROM my_image
ENV http_proxy <the_host_ip_address:port>
ENV https_proxy <the_host_ip_address:port>

score 2 · Accepted Answer · answered Jul 25 '23 at 08:00

2

Here is one way to set the host IP address in the Dockerfile:

FROM my_image

ARG HOST_IP
ENV http_proxy=$HOST_IP:port
ENV https_proxy=$HOST_IP:port

# Rest of the Dockerfile goes here

And then when building the image, you would pass the --build-arg flag to set the HOST_IP arg:

docker build --build-arg HOST_IP=$(hostname -i) -t myimage .

This will set the HOST_IP arg to the IP address of the host machine during build time.

The advantage of this method is that the host IP doesn't need to be hardcoded in the Dockerfile, it is set at build time.

answered Jul 25 '23 at 08:00

itsmedannyc

How to see the output of $(hostname -i)? – ccd Jul 25 '23 at 08:22
Just run it in your terminal: hostname -i – itsmedannyc Jul 25 '23 at 08:32
That command will output the same value as what the Dockerfile is going to use – itsmedannyc Jul 25 '23 at 08:34
@ccd please mark the answer as complete if it helped you :) – itsmedannyc Jul 26 '23 at 07:06

Maksim Eliseev · Answer 2 · 2023-07-25T08:10:27.377

You can pass any argument variables while building a docker-image and use them in the Dockerfile. For example:

FROM my_image
ARG host
ARG port
ENV http_proxy $host:$port
ENV https_proxy $host:$port

And the command for building a docker-image will look like this:

docker build --build-arg host=<the_host_ip_address> --build-arg port=<port> .

There is a useful article on the baeldung.com

UPD

I've already found a more detailed answer. Look at this.

2 Answers2