RUN echo -e "deb http ... " prepares a wrong contents of the target file

Question

Host with Ubuntu 16.04.2.

Docker version 17.06.0-ce.

Dockerfile

RUN echo -e "deb http://nginx.org/packages/mainline/ubuntu/ xenial nginx\ndeb-src http://nginx.org/packages/mainline/ubuntu/ xenial nginx" | tee /etc/apt/sources.list.d/nginx.list

This results in in /etc/apt/sources.list.d/nginx.list:

-e deb http://nginx.org/packages/mainline/ubuntu/ xenial nginx
deb-src http://nginx.org/packages/mainline/ubuntu/ xenial nginx

Well, as if interpretation of backslash escapes works. But this "-e" has occurred in the file.

And then such image can't be built.

Could you give me a kick here?

Answer 1

Try using the bash shell for the echo command instead. Docker by default uses the sh shell and for some reason it doesn't like the -e characters and had echo'ed it as part of its input.

To fix this;

Update to:

RUN bash -c 'echo -e "deb http://nginx.org/packages/mainline/ubuntu/ xenial nginx\ndeb-src http://nginx.org/packages/mainline/ubuntu/ xenial nginx" | tee /etc/apt/sources.list.d/nginx.list'

Outputs:

root@87944d07f493:/etc/apt/sources.list.d# cat nginx.list deb http://nginx.org/packages/mainline/ubuntu/ xenial nginx deb-src http://nginx.org/packages/mainline/ubuntu/ xenial nginx

You can replicate this "docker problem" by switching to sh on your current terminal session and then do the same echo command again.