How to silently install r-base in an ubuntu docker image - r

Question

I need to install r-base within an ubuntu:18.04 dockerimage. I am doing this while building my image via
RUN apt-get update; apt-get install -y r-base [many other packages]
along with many other package installations. The problem is, that while setting up r-base at the end of the installation process, it asks for user input for timezone followed by city within the specified timezone. I obviously cannot enter the data while building the container. How would I manage to install r-base anyways?

Answer 1

From AskUbuntu, you should set
ENV DEBIAN_FRONTEND=noninteractive

Answer 2

Directly taken from: https://github.com/rocker-org/rocker/blob/master/r-ubuntu/Dockerfile
FROM ubuntu:bionic
LABEL org.label-schema.license="GPL-2.0" \
org.label-schema.vcs-url="https://github.com/rocker-org/r-apt" \
org.label-schema.vendor="Rocker Project" \
maintainer="Dirk Eddelbuettel <edd#debian.org>"
## Set a default user. Available via runtime flag `--user docker`
## Add user to 'staff' group, granting them write privileges to /usr/local/lib/R/site.library
## User should also have & own a home directory (for rstudio or linked volumes to work properly).
RUN useradd docker \
&& mkdir /home/docker \
&& chown docker:docker /home/docker \
&& addgroup docker staff
RUN apt-get update \
&& apt-get install -y --no-install-recommends \
software-properties-common \
ed \
less \
locales \
vim-tiny \
wget \
ca-certificates \
&& add-apt-repository --enable-source --yes "ppa:marutter/rrutter3.5" \
&& add-apt-repository --enable-source --yes "ppa:marutter/c2d4u3.5"
## Configure default locale, see https://github.com/rocker-org/rocker/issues/19
RUN echo "en_US.UTF-8 UTF-8" >> /etc/locale.gen \
&& locale-gen en_US.utf8 \
&& /usr/sbin/update-locale LANG=en_US.UTF-8
ENV LC_ALL en_US.UTF-8
ENV LANG en_US.UTF-8
## This was not needed before but we need it now
ENV DEBIAN_FRONTEND noninteractive
# Now install R and littler, and create a link for littler in /usr/local/bin
# Default CRAN repo is now set by R itself, and littler knows about it too
# r-cran-docopt is not currently in c2d4u so we install from source
RUN apt-get update \
&& apt-get install -y --no-install-recommends \
littler \
r-base \
r-base-dev \
r-recommended \
&& ln -s /usr/lib/R/site-library/littler/examples/install.r /usr/local/bin/install.r \
&& ln -s /usr/lib/R/site-library/littler/examples/install2.r /usr/local/bin/install2.r \
&& ln -s /usr/lib/R/site-library/littler/examples/installGithub.r /usr/local/bin/installGithub.r \
&& ln -s /usr/lib/R/site-library/littler/examples/testInstalled.r /usr/local/bin/testInstalled.r \
&& install.r docopt \
&& rm -rf /tmp/downloaded_packages/ /tmp/*.rds \
&& rm -rf /var/lib/apt/lists/*
CMD ["bash"]