diff --git a/all-spark-notebook/Dockerfile b/all-spark-notebook/Dockerfile
index 2bffec5f..5f6a7132 100644
--- a/all-spark-notebook/Dockerfile
+++ b/all-spark-notebook/Dockerfile
@@ -25,13 +25,19 @@ RUN conda install --quiet --yes \
     'r-irkernel=0.7*' \
     'r-ggplot2=2.2*' \
     'r-sparklyr=0.5*' \
-    'r-rcurl=1.95*' && conda clean -tipsy
+    'r-rcurl=1.95*' && \
+    conda clean -tipsy && \
+    fix-permissions $CONDA_DIR
 
 # Apache Toree kernel
-RUN pip --no-cache-dir install https://dist.apache.org/repos/dist/dev/incubator/toree/0.2.0/snapshots/dev1/toree-pip/toree-0.2.0.dev1.tar.gz
-RUN jupyter toree install --sys-prefix
+RUN pip install --no-cache-dir \
+    https://dist.apache.org/repos/dist/dev/incubator/toree/0.2.0/snapshots/dev1/toree-pip/toree-0.2.0.dev1.tar.gz \
+    && \
+    jupyter toree install --sys-prefix && \
+    fix-permissions $CONDA_DIR
 
 # Spylon-kernel
 RUN conda install --quiet --yes 'spylon-kernel=0.4*' && \
-    conda clean -tipsy
-RUN python -m spylon_kernel install --sys-prefix
+    conda clean -tipsy && \
+    python -m spylon_kernel install --sys-prefix && \
+    fix-permissions $CONDA_DIR
diff --git a/base-notebook/Dockerfile b/base-notebook/Dockerfile
index e9bda554..70d728bb 100644
--- a/base-notebook/Dockerfile
+++ b/base-notebook/Dockerfile
@@ -33,25 +33,34 @@ RUN wget --quiet https://github.com/krallin/tini/releases/download/v0.10.0/tini
     chmod +x /usr/local/bin/tini
 
 # Configure environment
-ENV CONDA_DIR /opt/conda
-ENV PATH $CONDA_DIR/bin:$PATH
-ENV SHELL /bin/bash
-ENV NB_USER jovyan
-ENV NB_UID 1000
-ENV HOME /home/$NB_USER
-ENV LC_ALL en_US.UTF-8
-ENV LANG en_US.UTF-8
-ENV LANGUAGE en_US.UTF-8
+ENV CONDA_DIR=/opt/conda \
+    SHELL=/bin/bash \
+    NB_USER=jovyan \
+    NB_UID=1000 \
+    NB_OWNER_GROUP=user-writable \
+    NB_OWNER_GID=10000 \
+    LC_ALL=en_US.UTF-8 \
+    LANG=en_US.UTF-8 \
+    LANGUAGE=en_US.UTF-8
+ENV PATH=$CONDA_DIR/bin:$PATH \
+    HOME=/home/$NB_USER
 
+ADD fix-permissions /usr/local/bin/fix-permissions
 # Create jovyan user with UID=1000 and in the 'users' group
+# and the user-writable group, which owns all of the
+# files we want users to write (/home/jovyan, packages)
 RUN useradd -m -s /bin/bash -N -u $NB_UID $NB_USER && \
     mkdir -p $CONDA_DIR && \
-    chown $NB_USER $CONDA_DIR
+    chown $NB_USER $CONDA_DIR && \
+    groupadd -g $NB_OWNER_GID $NB_OWNER_GROUP && \
+    usermod -G $NB_OWNER_GROUP $NB_USER && \
+    fix-permissions /home/$NB_USER
 
 USER $NB_USER
 
 # Setup work directory for backward-compatibility
-RUN mkdir /home/$NB_USER/work
+RUN mkdir /home/$NB_USER/work && \
+    fix-permissions /home/$NB_USER
 
 # Install conda as jovyan and check the md5 sum provided on the download site
 ENV MINICONDA_VERSION 4.3.21
@@ -65,14 +74,16 @@ RUN cd /tmp && \
     $CONDA_DIR/bin/conda config --system --set auto_update_conda false && \
     $CONDA_DIR/bin/conda config --system --set show_channel_urls true && \
     $CONDA_DIR/bin/conda update --all && \
-    conda clean -tipsy
+    conda clean -tipsy && \
+    fix-permissions $CONDA_DIR
 
 # Install Jupyter Notebook and Hub
 RUN conda install --quiet --yes \
     'notebook=5.0.*' \
     'jupyterhub=0.7.*' \
     'jupyterlab=0.27.*' \
-    && conda clean -tipsy
+    && conda clean -tipsy && \
+    fix-permissions $CONDA_DIR
 
 USER root
 
@@ -88,7 +99,7 @@ COPY start.sh /usr/local/bin/
 COPY start-notebook.sh /usr/local/bin/
 COPY start-singleuser.sh /usr/local/bin/
 COPY jupyter_notebook_config.py /etc/jupyter/
-RUN chown -R $NB_USER:users /etc/jupyter/
+RUN fix-permissions /etc/jupyter/
 
 # Switch back to jovyan to avoid accidental container runs as root
 USER $NB_USER
diff --git a/base-notebook/README.md b/base-notebook/README.md
index 11214876..1870cdcd 100644
--- a/base-notebook/README.md
+++ b/base-notebook/README.md
@@ -58,6 +58,9 @@ You may customize the execution of the Docker container and the command it is ru
 * `-e NB_GID=100` - Specify the gid of the `jovyan` user. Useful to mount host volumes with specific file ownership. For this option to take effect, you must run the container with `--user root`. (The `start-notebook.sh` script will `su jovyan` after adjusting the group id.)
 * `-e GRANT_SUDO=yes` - Gives the `jovyan` user passwordless `sudo` capability. Useful for installing OS packages. For this option to take effect, you must run the container with `--user root`. (The `start-notebook.sh` script will `su jovyan` after adding `jovyan` to sudoers.) **You should only enable `sudo` if you trust the user or if the container is running on an isolated host.**
 * `-v /some/host/folder/for/work:/home/jovyan/work` - Mounts a host machine directory as folder in the container. Useful when you want to preserve notebooks and other work even after the container is destroyed. **You must grant the within-container notebook user or group (`NB_UID` or `NB_GID`) write access to the host directory (e.g., `sudo chown 1000 /some/host/folder/for/work`).**
+* `--group-add user-writable` - use this argument if you are also specifying
+  a specific user id to launch the container (`-u 5000`), rather than launching the container as root and relying on NB_UID and NB_GID to set the user and group.
+
 
 ## SSL Certificates
 
@@ -111,11 +114,6 @@ conda install some-package
 ```python
 # Spawn user containers from this image
 c.DockerSpawner.container_image = 'jupyter/base-notebook'
-
-# Have the Spawner override the Docker run command
-c.DockerSpawner.extra_create_kwargs.update({
-	'command': '/usr/local/bin/start-singleuser.sh'
-})
 ```
 
 ### start.sh
@@ -137,3 +135,4 @@ This script is particularly useful when you derive a new Dockerfile from this im
 ### Others
 
 You can bypass the provided scripts and specify your an arbitrary start command. If you do, keep in mind that certain features documented above will not function (e.g., `GRANT_SUDO`).
+
diff --git a/base-notebook/fix-permissions b/base-notebook/fix-permissions
new file mode 100755
index 00000000..588e59a2
--- /dev/null
+++ b/base-notebook/fix-permissions
@@ -0,0 +1,27 @@
+#!/bin/bash
+# set permissions on a directory
+# after any installation, if a directory needs to be (human) user-writable,
+# run this script on it.
+# It will make everything in the directory owned by the group $NB_OWNER_GROUP
+# and writable by that group.
+# Deployments that want to set a specific user id can preserve permissions
+# by adding the `--group-add user-writable` line to `docker run`.
+
+# uses find to avoid touching files that already have the right permissions,
+# which would cause massive image explosion
+
+# right permissions are:
+# group=$NB_OWNER_GROUP
+# AND permissions include group rwX (directory-execute)
+
+set -e
+
+for d in $@; do
+  find "$d" \
+    ! \( \
+      -group $NB_OWNER_GROUP \
+      -a -perm -g+rwX  \
+    \) \
+    -exec chgrp $NB_OWNER_GROUP {} \; \
+    -exec chmod g+rwX {} \;
+done
diff --git a/base-notebook/start.sh b/base-notebook/start.sh
index 099af2b6..c5f957f7 100755
--- a/base-notebook/start.sh
+++ b/base-notebook/start.sh
@@ -13,14 +13,6 @@ if [ $(id -u) == 0 ] ; then
     if [ "$NB_UID" != $(id -u $NB_USER) ] ; then
         echo "Set user UID to: $NB_UID"
         usermod -u $NB_UID $NB_USER
-        # Careful: $HOME might resolve to /root depending on how the
-        # container is started. Use the $NB_USER home path explicitly.
-        for d in "$CONDA_DIR" "$JULIA_PKGDIR" "/home/$NB_USER"; do
-            if [[ ! -z "$d" && -d "$d" ]]; then
-                echo "Set ownership to uid $NB_UID: $d"
-                chown -R $NB_UID "$d"
-            fi
-        done
     fi
 
     # Change GID of NB_USER to NB_GID if NB_GID is passed as a parameter
diff --git a/datascience-notebook/Dockerfile b/datascience-notebook/Dockerfile
index 7f98a99a..a3e5a06e 100644
--- a/datascience-notebook/Dockerfile
+++ b/datascience-notebook/Dockerfile
@@ -30,7 +30,8 @@ RUN . /etc/os-release && \
     echo "push!(Libdl.DL_LOAD_PATH, \"$CONDA_DIR/lib\")" >> /usr/etc/julia/juliarc.jl && \
     # Create JULIA_PKGDIR \
     mkdir $JULIA_PKGDIR && \
-    chown -R $NB_USER:users $JULIA_PKGDIR
+    chown $NB_USER $JULIA_PKGDIR && \
+    fix-permissions $JULIA_PKGDIR
 
 USER $NB_USER
 
@@ -52,7 +53,9 @@ RUN conda config --system --add channels r && \
     'r-caret=6.0*' \
     'r-rcurl=1.95*' \
     'r-crayon=1.3*' \
-    'r-randomforest=4.6*' && conda clean -tipsy
+    'r-randomforest=4.6*' && \
+    conda clean -tipsy && \
+    fix-permissions $CONDA_DIR
 
 # Add Julia packages
 # Install IJulia as jovyan and then move the kernelspec out
@@ -72,5 +75,6 @@ RUN julia -e 'Pkg.init()' && \
     # move kernelspec out of home \
     mv $HOME/.local/share/jupyter/kernels/julia* $CONDA_DIR/share/jupyter/kernels/ && \
     chmod -R go+rx $CONDA_DIR/share/jupyter && \
-    rm -rf $HOME/.local
+    rm -rf $HOME/.local && \
+    fix-permissions $JULIA_PKGDIR $CONDA_DIR/share/jupyter
 
diff --git a/r-notebook/Dockerfile b/r-notebook/Dockerfile
index c9559d54..ed117684 100644
--- a/r-notebook/Dockerfile
+++ b/r-notebook/Dockerfile
@@ -32,4 +32,6 @@ RUN conda install --quiet --yes \
     'r-caret=6.0*' \
     'r-rcurl=1.95*' \
     'r-crayon=1.3*' \
-    'r-randomforest=4.6*' && conda clean -tipsy
+    'r-randomforest=4.6*' && \
+    conda clean -tipsy && \
+    fix-permissions $CONDA_DIR
diff --git a/scipy-notebook/Dockerfile b/scipy-notebook/Dockerfile
index 8f528eef..130d624e 100644
--- a/scipy-notebook/Dockerfile
+++ b/scipy-notebook/Dockerfile
@@ -42,13 +42,14 @@ RUN conda install --quiet --yes \
     'beautifulsoup4=4.5.*' \
     'xlrd'  && \
     conda remove --quiet --yes --force qt pyqt && \
-    conda clean -tipsy
-
-# Activate ipywidgets extension in the environment that runs the notebook server
-RUN jupyter nbextension enable --py widgetsnbextension --sys-prefix
+    conda clean -tipsy && \
+    # Activate ipywidgets extension in the environment that runs the notebook server
+    jupyter nbextension enable --py widgetsnbextension --sys-prefix && \
+    fix-permissions $CONDA_DIR
 
 # Import matplotlib the first time to build the font cache.
 ENV XDG_CACHE_HOME /home/$NB_USER/.cache/
-RUN MPLBACKEND=Agg python -c "import matplotlib.pyplot"
+RUN MPLBACKEND=Agg python -c "import matplotlib.pyplot" && \
+    fix-permissions /home/$NB_USER
 
 USER $NB_USER
diff --git a/tensorflow-notebook/Dockerfile b/tensorflow-notebook/Dockerfile
index 15808556..24b3d24f 100644
--- a/tensorflow-notebook/Dockerfile
+++ b/tensorflow-notebook/Dockerfile
@@ -4,5 +4,7 @@ FROM jupyter/scipy-notebook
 
 MAINTAINER Jupyter Project <jupyter@googlegroups.com>
 
-# Install Python 3 Tensorflow
-RUN conda install --quiet --yes 'tensorflow=1.0*'
+# Install Tensorflow
+RUN conda install --quiet --yes 'tensorflow=1.0*' && \
+    conda clean -tipsy && \
+    fix-permissions $CONDA_DIR