prevent the command "cassandra start" from starting a cluster

patch by Robert Stupp; reviewed by Michael Shuler for CASSANDRA-8142

CHANGES.txt

@@ -1,4 +1,5 @@
 3.2
+ * Prevent running Cassandra as root (CASSANDRA-8142)
  * bound maximum in-flight commit log replay mutation bytes to 64 megabytes (CASSANDRA-8639)
  * Normalize all scripts (CASSANDRA-10679)
  * Make compression ratio much more accurate (CASSANDRA-10225)

NEWS.txt

@@ -25,6 +25,7 @@ New features
 Upgrading
 ---------
    - The compression ratio metrics computation has been modified to be more accurate.
+   - Running Cassandra as root is prevented by default.
 
 
 3.1

bin/cassandra

@@ -211,7 +211,7 @@ launch_service()
 }
 
 # Parse any command line options.
-args=`getopt vfhp:bD:H:E: "$@"`
+args=`getopt vRfhp:bD:H:E: "$@"`
 eval set -- "$args"
 
 classname="org.apache.cassandra.service.CassandraDaemon"
@@ -234,6 +234,10 @@ while true; do
             "$JAVA" -cp "$CLASSPATH" org.apache.cassandra.tools.GetVersion
             exit 0
         ;;
+        -R)
+            allow_root="yes"
+            shift
+        ;;
         -D)
             properties="$properties -D$2"
             shift 2
@@ -248,15 +252,27 @@ while true; do
         ;;
         --)
             shift
+            if [ "x$*" != "x" ] ; then
+                echo "Error parsing arguments! Unknown argument \"$*\"" >&2
+                exit 1
+            fi
             break
         ;;
         *)
-            echo "Error parsing arguments!" >&2
+            echo "Error parsing arguments! Unknown argument \"$1\"" >&2
             exit 1
         ;;
     esac
 done
 
+if [ "x$allow_root" != "xyes" ] ; then
+    if [ "`id -u`" = "1" ] || [ "`id -g`" = "0" ] ; then
+        echo "Running Cassandra as root user or group is not recommended - please start Cassandra using a different system user."
+        echo "If you really want to force running Cassandra as root, use -R command line option."
+        exit 1
+    fi
+fi
+
 # see CASSANDRA-7254
 "$JAVA" -cp "$CLASSPATH" $JVM_OPTS 2>&1 | grep -q 'Error: Exception thrown by the agent : java.lang.NullPointerException'
 if [ $? -ne "1" ]; then