I'm trying to build a Docker image, but it fails because one of the packages I'm trying to get with apt install prompts the user during the install process. I would like to reply to this prompt, but I can't figure out how to do it non-interactively.
I'm building a Docker image, and my Dockerfile has the following line:
RUN apt install -y texlive-latex-extra
(This package has some LaTeX libraries that I need.)
During installation, this halts with:
Setting up tzdata (2018d-1) ...
debconf: unable to initialize frontend: Dialog
debconf: (TERM is not set, so the dialog frontend is not usable.)
debconf: falling back to frontend: Readline
Configuring tzdata
------------------
Please select the geographic area in which you live. Subsequent configuration
questions will narrow this down by presenting a list of cities, representing
the time zones in which they are located.
1. Africa 6. Asia 11. System V timezones
2. America 7. Atlantic Ocean 12. US
3. Antarctica 8. Europe 13. None of the above
4. Australia 9. Indian Ocean
5. Arctic Ocean 10. Pacific Ocean
Geographic area:
At this point, it is waiting for some input. (There's another prompt after this for selecting timezone—I assume this is important to know for the \today directive in LaTeX files. ¯\_(ツ)_/¯)
How can I answer this non-interactively?
I've tried doing this:
apt install -y texlive-latex-extra <(echo 12 && echo 2)
and this:
echo 12 && echo 2 | apt install -y texlive-latex-extra
The first one died with this error:
apt install -y texlive-latex-extra <(echo 12 && echo 9)
and the second one seemed to have no effect.
For reference, here is my Dockerfile up until this point:
FROM ubuntu:latest
RUN apt update && apt upgrade -y && apt install -y curl bzip2 tar make gcc wget gnupg unzip
RUN apt install -y texlive
RUN apt install -y nodejs npm git
RUN npm install -g bower
RUN apt install -y texlive-latex-extra
I found something close here which suggested running apt install with DEBIAN_FRONTEND=noninteractive. This solved my problem sufficiently. :) However, I still would like to know how to respond to prompts, as the solution offered there only offered how to suppress them.
If you want to script a terminal interaction, you could use expect on Linux (that might not be very easy; you need to predict the interactions).
Remember that terminal emulators are complex and arcane things (because terminals like VT100 have been complex). See termios(3), pty(7) and read The Tty demystified.