move nss_wrapper setup code to an entrypoint

the goal is to allow users to shell into the cluster pods, or start a
container manually, without having to manually setup nss_wrapper in
their environment.

everyone stumbles on getting the nss_wrapper env setup the first
time. the resulting error is about failure to login from within the
hadoop code, which is confusing. everyone then struggles with the
manual nature of setting up the env after they overcome the strange
login error.

Dockerfile

@@ -35,5 +35,7 @@ RUN rm -rf /tmp/scripts
 # Switch to the user 185 for OpenShift usage
 USER 185
 
+ENTRYPOINT ["/opt/spark/bin/entrypoint"]
+
 # Start the main process
 CMD ["/opt/spark/bin/launch.sh"]

scripts/spark/added/entrypoint

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+# spark likes to be able to lookup a username for the running UID, if
+# no name is present fake it.
+cat /etc/passwd > /tmp/passwd
+echo "$(id -u):x:$(id -u):$(id -g):dynamic uid:$SPARK_HOME:/bin/false" >> /tmp/passwd
+
+export NSS_WRAPPER_PASSWD=/tmp/passwd
+# NSS_WRAPPER_GROUP must be set for NSS_WRAPPER_PASSWD to be used
+export NSS_WRAPPER_GROUP=/etc/group
+
+export LD_PRELOAD=libnss_wrapper.so
+
+exec "$@"

scripts/spark/added/launch.sh

@@ -1,16 +1,5 @@
 #!/bin/bash
 
-# spark likes to be able to lookup a username for the running UID, if
-# no name is present fake it.
-cat /etc/passwd > /tmp/passwd
-echo "$(id -u):x:$(id -u):$(id -g):dynamic uid:$SPARK_HOME:/bin/false" >> /tmp/passwd
-
-export NSS_WRAPPER_PASSWD=/tmp/passwd
-# NSS_WRAPPER_GROUP must be set for NSS_WRAPPER_PASSWD to be used
-export NSS_WRAPPER_GROUP=/etc/group
-
-export LD_PRELOAD=libnss_wrapper.so
-
 # If the UPDATE_SPARK_CONF_DIR dir is non-empty,
 # copy the contents to $SPARK_HOME/conf
 if [ -d "$UPDATE_SPARK_CONF_DIR" ]; then

scripts/spark/install

@@ -5,6 +5,9 @@ set -e
 SCRIPT_DIR=$(dirname $0)
 ADDED_DIR=${SCRIPT_DIR}/added
 
+mv $ADDED_DIR/entrypoint $SPARK_HOME/bin/
+chmod +x $SPARK_HOME/bin/entrypoint
+
 mv $ADDED_DIR/launch.sh $SPARK_HOME/bin/
 chmod +x $SPARK_HOME/bin/launch.sh