Docker – How to get docker build to overwrite a file

The switch you need is --parents, e.g.:

jim@prometheus:~$ cp --parents test/1/.moo test2/
jim@prometheus:~$ ls -la test2/
total 42
drwxr-xr-x   3 jim jim    72 2010-09-14 09:32 .
drwxr-xr-x 356 jim jim 43136 2010-09-14 09:32 ..
drwxr-xr-x   3 jim jim    72 2010-09-14 09:32 test
jim@prometheus:~$ ls -la test2/test/1/.moo
-rw-r--r-- 1 jim jim 0 2010-09-14 09:32 test2/test/1/.moo

From the official Nginx docker file:

Using environment variables in nginx configuration:

Out-of-the-box, Nginx doesn't support using environment variables inside most configuration blocks.

But envsubst may be used as a workaround if you need to generate your nginx configuration dynamically before nginx starts.

Here is an example using docker-compose.yml:

image: nginx
volumes:
 - ./mysite.template:/etc/nginx/conf.d/mysite.template
ports:
 - "8080:80"
environment:
 - NGINX_HOST=foobar.com
 - NGINX_PORT=80
command: /bin/bash -c "envsubst < /etc/nginx/conf.d/mysite.template > /etc/nginx/conf.d/default.conf && nginx -g 'daemon off;'" 

The mysite.template file may then contain variable references like this :

listen ${NGINX_PORT};

Update:

But you know this caused to its Nginx variables like this:

proxy_set_header        X-Forwarded-Host $host;

damaged to:

proxy_set_header        X-Forwarded-Host ;

So, to prevent that, i use this trick:

I have a script to run Nginx, that used on the docker-compose file as command option for Nginx server, i named it run_nginx.sh:

#!/usr/bin/env bash
export DOLLAR='$'
envsubst < nginx.conf.template > /etc/nginx/nginx.conf
nginx -g "daemon off;"

And because of defined new DOLLAR variable on run_nginx.sh script, now content of my nginx.conf.template file for Nginx itself variable is like this:

proxy_set_header        X-Forwarded-Host ${DOLLAR}host;

And for my defined variable is like this:

server_name  ${WEB_DOMAIN} www.${WEB_DOMAIN};

Also here, there is my real use case for that.