create docker user

Author: Kirill Müller

Dockerfile

@@ -4,6 +4,17 @@ FROM debian:latest
 #
 MAINTAINER "Kirill Müller" <krlmlr+docker@mailbox.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, but also be able to sudo
+RUN useradd docker \
+        && passwd -d docker \
+        && mkdir /home/docker \
+        && chown docker:docker /home/docker \
+        && addgroup docker staff \
+        && addgroup docker sudo \
+        && true
+
 # Install packages
 RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get -y install openssh-server sudo
 RUN mkdir -p /var/run/sshd && sed -i "s/UsePrivilegeSeparation.*/UsePrivilegeSeparation no/g" /etc/ssh/sshd_config