tee mount & user namespace

Dockerfile

@@ -3,6 +3,8 @@ FROM alpine:3.9
 CMD set -x \
     && mkdir -p /prop-test/src /prop-test/vol/mp \
     && mount --bind /prop-test/src /prop-test/vol/mp \
-    && date -Is > /prop-test/src/mount-timestamp \
+    && date -Is | tee /prop-test/src/mount-timestamp \
+    && readlink /proc/self/ns/mnt | tee /prop-test/src/mntns \
+    && readlink /proc/self/ns/user | tee /prop-test/src/userns \
     && grep /prop-test /proc/self/mountinfo | tee /prop-test/src/mountinfo-container \
     && sleep 21m