如何在启动时动态地将docker容器ip设置为环境变量？

Question

I want to export docker container hostname as an environment variable which I can later use in my app. In my docker file I call my script "run" as last command

CMD run

The run file is executable and works fine with rest of commands I perform but before them I want to export container hostname to an env. variable as follows

"run" File Try 1

#!/bin/bash
export DOCKER_MACHINE_IP=`hostname -i`
my_other_commands
exec tail -f /dev/null

But when I enter docker container and check, the variable is not set. If I use

echo $DOCKER_MACHINE_IP

in run file after exporting, it shows ip on console when I try

docker logs

I also tried sourcing another script from "run" file as follows

"run" File Try 2

#!/bin/bash
source ./bin/script
my_other_commands 
exec tail -f /dev/null

and the script again contains the export command. But this also does not set the environment variable. What I am doing wrong?

Answer 1

When you execute a script, any environment variable set by that script will be lost when the script exits.

But for both the cases you've posted above the environment variable should be accessible for the commands in your scripts, but when you enter the docker container via docker run you will get a new shell, which does not contain your variable.

tl;dr Your exported environment variable will only be available to sub shells of the shell which set the variable. And if you need it when logging in you should source the ./bin/script file.