Improved handling of environment variables for NB_USER in docker.

Dockerfile

@@ -39,12 +39,21 @@ RUN echo "%apt-users ALL=(ALL) NOPASSWD: /usr/bin/apt update, /usr/bin/apt insta
 #######################################################################################################
 ARG GO_VERSION=1.23.2
 ENV GOROOT=/usr/local/go
-ENV GOPATH=/opt/go
+ENV GOPATH=$HOME/go
 ENV PATH=$PATH:$GOROOT/bin:$GOPATH/bin
 
-# Create Go directory for user -- that will not move if the user home directory is moved.
-USER root
-RUN mkdir ${GOPATH} && chown ${NB_USER}:users ${GOPATH}
+# Add exported variables to $NB_USER .profile: notice we start the docker as root, and it executes
+# JupyterLab with a `su -l $NB_USER`, so the environment variables are lost. We could use --preserve_environment
+# for GOROOT and GOPATH, but it feels safer to add these to .profile, so the autostart.sh script can also
+# execute `su -l $NB_USER -c "<some command>"` if it wants.
+USER $NB_USER
+WORKDIR ${HOME}
+RUN <<EOF
+  echo "NB_USER=${NB_USER}" >> .profile
+  echo "export PATH=${PATH}" >> .profile
+  echo "export GOPATH=${GOPATH}" >> .profile
+  echo "export GOROOT=${GOROOT}" >> .profile
+EOF
 
 USER root
 WORKDIR /usr/local

README.md

@@ -109,13 +109,8 @@ docker run -it --rm -p 8888:8888 -v "${PWD}":/notebooks janpfeifer/gonb_jupyterl
 
 Then copy&paste the URL that it outputs in your browser.
 
-#### Docker Customized Initialization
-
-If the container you run `gonb` needs some custom initialization, and you don't want to simply edit the dockerfile and 
-create your own docker, just create a files `autostart.sh` in the directory mounted under `/notebooks` in the container,
-owned by `root` and with executable permissions, and it will be executed at start up of the container by default.
-
-This allows you to download/install databases, or set up credentials, etc.
+**Note**: The docker allows for customization by running an arbitrary script at start up as `root`, which allows
+one to install any planned dependencies. See [docker.md](docs/docker.md) for details.
 
 ### Linux and macOS Installation Using Standard Go Tools
 

cmd/check_and_run_autostart.sh

@@ -6,10 +6,13 @@
 # Notice ${NOTEBOOKS} is /notebooks in the container, and is assumed to be mounted from the host directory that
 # will have the users notebooks.
 
+# Makes sure we are not using $NB_USER's GOPATH.
+export GOPATH=/root/go
+
 # Check if autostart.sh exists
 if [[ -f "${NOTEBOOKS}/autostart.sh" ]]; then
   # Check if it's owned by root and is executable
-  if [[ "$(stat -c '%U' ${NOTEBOOKS}/autostart.sh)" = "root" && -x "${NOTEBOOKS}/autostart.sh" ]]; then
+  if [[ "$(stat -c '%U' "${NOTEBOOKS}/autostart.sh")" = "root" && -x "${NOTEBOOKS}/autostart.sh" ]]; then
     # Run autostart.sh as root
     echo "Running autostart.sh as root..."
     "${NOTEBOOKS}/autostart.sh"
@@ -21,10 +24,5 @@ else
   echo "No autostart.sh initialization script."
 fi
 
-
-echo "Current directory:"
-pwd
-
-# Switch to the $NB_USER, preserving environment variables.
-# Notice $PATH gets rewritten anyway, so we need to explicitly set it again with the new user.
-su --preserve-environment  $NB_USER -c "export PATH=${PATH} ; jupyter lab"
+# Run JupyterLab from $NOTEBOOKS as user $NB_USER.
+su -l "${NB_USER}" -c "cd \"${NOTEBOOKS}\" ; jupyter lab"

docs/docker.md

@@ -0,0 +1,33 @@
+# Docker Customization
+
+If the container you run `gonb` needs some custom initialization, and you don't want to simply edit the dockerfile and
+create your own docker, just create the file `autostart.sh` in the directory mounted under `/notebooks` in the container,
+owned by `root` and with executable permissions, and it will be executed at start up of the container by default.
+
+This allows you to download/install databases, or set up credentials, etc.
+
+Example of an `autostart.sh` that:
+
+- Sets the timezone
+- Installs [`nats`](github.com/nats-io/natscli/) for the jupyer user (given by `$NB_USER`).
+
+```
+# Set the German timezone (so time.Now() returns German time)
+apt-get install -y tzdata
+ln -sf /usr/share/zoneinfo/Europe/Berlin /etc/localtime
+
+# some locale magic to make "date" answer with German format
+echo 'de_DE.UTF-8 UTF-8' >> /etc/locale.gen
+locale-gen
+echo 'LC_ALL="de_DE.utf8"' > /etc/default/locale
+export LC_ALL="de_DE.UTF-8"
+dpkg-reconfigure locales
+
+# check that it works
+date
+
+# Installing Go tools for $NB_USER.
+su -l "$NB_USER" -c "go install github.com/nats-io/natscli/nats@latest"
+```
+
+More details in the `Dockerfile` and in the small start script `cmd/check_and_run_autostart.sh`.