title: Kafka Connect failed to start
body: <p>I installed kafka confluent oss 4.0 on a fresh linux centos 7 but kafka connect failed to start.</p>
  
  <p>Steps to reproduce :</p>
  
  <pre><code> - Install Oracle JDK 8
   - Copy confluent-4.0.0 folder on opt/confluent-4.0.0
   - Run /opt/confluent-4.0.0/confluent start
  </code></pre>
  
  <p>Result :</p>
  
  <pre><code>Starting zookeeper
  zookeeper is [UP]
  Starting kafka
  kafka is [UP]
  Starting schema-registry
  schema-registry is [UP]
  Starting kafka-rest
  kafka-rest is [UP]
  Starting connect
  \Kafka Connect failed to start
  connect is [DOWN]
  </code></pre>
  
  <p>Error Log (connect.stderr) :</p>
  
  <pre><code>Exception in thread "main" java.lang.NoClassDefFoundError: io/confluent/connect/storage/StorageSinkConnectorConfig
          at java.lang.ClassLoader.defineClass1(Native Method)
          at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
          at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
          at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
          at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
          at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
          at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
          at java.security.AccessController.doPrivileged(Native Method)
          at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
          at org.apache.kafka.connect.runtime.isolation.PluginClassLoader.loadClass(PluginClassLoader.java:54)
          at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
          at java.lang.Class.getDeclaredConstructors0(Native Method)
          at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671)
          at java.lang.Class.getConstructor0(Class.java:3075)
          at java.lang.Class.newInstance(Class.java:412)
          at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.getPluginDesc(DelegatingClassLoader.java:279)
          at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.scanPluginPath(DelegatingClassLoader.java:260)
          at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.scanUrlsAndAddPlugins(DelegatingClassLoader.java:201)
          at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.registerPlugin(DelegatingClassLoader.java:193)
          at org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader.initLoaders(DelegatingClassLoader.java:153)
          at org.apache.kafka.connect.runtime.isolation.Plugins.&lt;init&gt;(Plugins.java:47)
          at org.apache.kafka.connect.cli.ConnectDistributed.main(ConnectDistributed.java:70)
  Caused by: java.lang.ClassNotFoundException: io.confluent.connect.storage.StorageSinkConnectorConfig
          at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
          at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
          at org.apache.kafka.connect.runtime.isolation.PluginClassLoader.loadClass(PluginClassLoader.java:62)
          at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
          ... 22 more
  </code></pre>
  
  <p>Additional informations :</p>
  
  <p>Java version :</p>
  
  <pre><code>java version "1.8.0_151"
  Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
  Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode
  </code></pre>
  
  <p>Centos version :</p>
  
  <pre><code>centos-release-7-4.1708.el7.centos.x86_64
  </code></pre>
  
  <p>[Edit : 30/11/2017]
  Editing plugin.path variables in every properties files didn't fix the problem.</p>
  
  <p>List of files containing 'plugin.path' variable :</p>
  
  <pre><code>./etc/schema-registry/connect-avro-distributed.properties:84:plugin.path=/opt/confluent-4.0.0/share/java
  ./etc/schema-registry/connect-avro-standalone.properties:51:plugin.path=/opt/confluent-4.0.0/share/java
  ./etc/kafka/connect-distributed.properties:95:plugin.path=/opt/confluent-4.0.0/share/java
  ./etc/kafka/connect-standalone.properties:50:plugin.path=/opt/confluent-4.0.0/share/java
  </code></pre>