diff --git a/Dockerfile b/Dockerfile
index 9813841..340070c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,6 +3,16 @@
 FROM ubuntu:16.04
 MAINTAINER Michael Stucki <michael@stucki.io>
 
+
+ENV \
+# ccache specifics
+    CCACHE_SIZE=50G \
+    CCACHE_DIR=/srv/ccache \
+    USE_CCACHE=1 \
+    CCACHE_COMPRESS=1 \
+# Extra include PATH, it may not include /usr/local/(s)bin on some systems
+    PATH=$PATH:/usr/local/bin/
+
 RUN sed -i 's/main$/main universe/' /etc/apt/sources.list \
  && export DEBIAN_FRONTEND=noninteractive \
  && apt-get update \
@@ -64,9 +74,8 @@ RUN \
     useradd --gid $hostgid --uid $hostuid --non-unique build && \
     rsync -a /etc/skel/ /home/build/
 
-RUN mkdir /home/build/bin
-RUN curl https://storage.googleapis.com/git-repo-downloads/repo > /home/build/bin/repo
-RUN chmod a+x /home/build/bin/repo
+RUN curl https://storage.googleapis.com/git-repo-downloads/repo > /usr/local/bin/repo \
+ && chmod a+x /usr/local/bin/repo
 
 # Add sudo permission
 RUN echo "build ALL=NOPASSWD: ALL" > /etc/sudoers.d/build
@@ -77,14 +86,10 @@ RUN chmod a+x /home/build/startup.sh
 # Fix ownership
 RUN chown -R build:build /home/build
 
-# Set global variables
-ADD android-env-vars.sh /etc/android-env-vars.sh
-RUN echo "source /etc/android-env-vars.sh" >> /etc/bash.bashrc
-
 VOLUME /home/build/android
 VOLUME /srv/ccache
 
-CMD /home/build/startup.sh
-
 USER build
 WORKDIR /home/build/android
+
+CMD /home/build/startup.sh
diff --git a/android-env-vars.sh b/android-env-vars.sh
deleted file mode 100644
index ff569ee..0000000
--- a/android-env-vars.sh
+++ /dev/null
@@ -1,4 +0,0 @@
-export PATH=/home/build/bin:$PATH
-export USE_CCACHE=1
-export CCACHE_DIR=/srv/ccache
-export CCACHE_COMPRESS=1
diff --git a/run.sh b/run.sh
index 45f6840..b6d20de 100755
--- a/run.sh
+++ b/run.sh
@@ -34,16 +34,18 @@ while [[ $# > 0 ]]; do
 done
 
 # Create shared folders
+# Although Docker would create non-existing directories on the fly,
+# we need to have them owned by the user (and not root), to be able
+# to write in them, which is a necessity for startup.sh
 mkdir -p $SOURCE
 mkdir -p $CCACHE
 
+command -v docker >/dev/null \
+	|| { echo "command 'docker' not found."; exit 1; }
+
 # Build image if needed
-IMAGE_EXISTS=$(docker images $REPOSITORY)
-if [ $? -ne 0 ]; then
-	echo "docker command not found"
-	exit $?
-elif [[ $FORCE_BUILD = 1 ]] || ! echo "$IMAGE_EXISTS" | grep -q "$TAG"; then
-	echo "Building Docker image $REPOSITORY:$TAG..."
+if [[ $FORCE_BUILD = 1 ]] || ! docker inspect $REPOSITORY:$TAG &>/dev/null; then
+
 	docker build \
 		--pull \
 		-t $REPOSITORY:$TAG \
@@ -52,9 +54,8 @@ elif [[ $FORCE_BUILD = 1 ]] || ! echo "$IMAGE_EXISTS" | grep -q "$TAG"; then
 		.
 
 	# After successful build, delete existing containers
-	IS_EXISTING=$(docker inspect -f '{{.Id}}' $CONTAINER 2>/dev/null) || true
-	if [[ -n $IS_EXISTING ]]; then
-		docker rm $CONTAINER
+	if docker inspect $CONTAINER &>/dev/null; then
+		docker rm $CONTAINER >/dev/null
 	fi
 fi
 
diff --git a/startup.sh b/startup.sh
index be5f50a..59e2c4b 100644
--- a/startup.sh
+++ b/startup.sh
@@ -1,12 +1,14 @@
 #!/bin/sh
 
 # Initialize ccache if needed
-if [ ! -f /srv/ccache/ccache.conf ]; then
+if [ ! -f ${CCACHE_DIR}/ccache.conf ]; then
 	echo "Initializing ccache in /srv/ccache..."
-	CCACHE_DIR=/srv/ccache ccache -M 50G
+	ccache -M ${CCACHE_SIZE}
 fi
 
-export USER="build"
+# in Docker, the USER variable is unset by default
+# but some programs (like jack toolchain) rely on it
+export USER="$(whoami)"
 
 # Launch screen session
 screen -s /bin/bash