use fewer layers

Author: Kirill Müller

Dockerfile

@@ -6,12 +6,13 @@ MAINTAINER "Kirill Müller" <krlmlr+docker@mailbox.org>
 
 # 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
 ADD set_root_pw.sh /set_root_pw.sh
 ADD run.sh /run.sh
 RUN chmod +x /*.sh
-RUN sed -i 's/PermitRootLogin without-password/PermitRootLogin yes/' /etc/ssh/sshd_config
-RUN touch /root/.Xauthority
+RUN mkdir -p /var/run/sshd && sed -i "s/UsePrivilegeSeparation.*/UsePrivilegeSeparation no/g" /etc/ssh/sshd_config
+  && sed -i 's/PermitRootLogin without-password/PermitRootLogin yes/' /etc/ssh/sshd_config \
+  && touch /root/.Xauthority \
+  && true
 
 ## 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