HDFS-12739. Add Support for SCM --init command. Contributed by Shashikant Banerjee.

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/ozone/OzoneConsts.java

@@ -147,6 +147,15 @@ public enum Versioning {NOT_DEFINED, ENABLED, DISABLED}
 
   public static final int INVALID_PORT = -1;
 
+  /**
+   * Type of the node.
+   */
+  public enum NodeType {
+    KSM,
+    SCM,
+    DATANODE
+  }
+
   private OzoneConsts() {
     // Never Constructed
   }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/common/InconsistentStorageStateException.java

@@ -0,0 +1,51 @@
+/**
+  * Licensed to the Apache Software Foundation (ASF) under one
+  * or more contributor license agreements.  See the NOTICE file
+  * distributed with this work for additional information
+  * regarding copyright ownership.  The ASF licenses this file
+  * to you under the Apache License, Version 2.0 (the
+  * "License"); you may not use this file except in compliance
+  * with the License.  You may obtain a copy of the License at
+  *
+  *     http://www.apache.org/licenses/LICENSE-2.0
+  *
+  * Unless required by applicable law or agreed to in writing, software
+  * distributed under the License is distributed on an "AS IS" BASIS,
+  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  * See the License for the specific language governing permissions and
+  * limitations under the License.
+  */
+package org.apache.hadoop.ozone.common;
+
+import java.io.File;
+import java.io.IOException;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+/**
+ * The exception is thrown when file system state is inconsistent
+ * and is not recoverable.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Evolving
+public class InconsistentStorageStateException extends IOException {
+  private static final long serialVersionUID = 1L;
+
+  public InconsistentStorageStateException(String descr) {
+    super(descr);
+  }
+
+  public InconsistentStorageStateException(File dir, String descr) {
+    super("Directory " + getFilePath(dir) + " is in an inconsistent state: "
+        + descr);
+  }
+
+  private static String getFilePath(File dir) {
+    try {
+      return dir.getCanonicalPath();
+    } catch (IOException e) {
+    }
+    return dir.getPath();
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/common/Storage.java

@@ -0,0 +1,249 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.ozone.common;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.DirectoryStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Properties;
+
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.fs.FileUtil;
+import org.apache.hadoop.ozone.OzoneConsts.NodeType;
+import org.apache.hadoop.util.Time;
+
+/**
+ * Storage information file. This Class defines the methods to check
+ * the consistency of the storage dir and the version file.
+ * <p>
+ * Local storage information is stored in a separate file VERSION.
+ * It contains type of the node,
+ * the storage layout version, the SCM id, and
+ * the KSM/SCM state creation time.
+ *
+ */
+@InterfaceAudience.Private
+public abstract class Storage {
+  private static final Logger LOG = LoggerFactory.getLogger(Storage.class);
+
+  protected static final String STORAGE_DIR_CURRENT = "current";
+  protected static final String STORAGE_FILE_VERSION = "VERSION";
+
+  private final NodeType nodeType;
+  private final File root;
+  private final File storageDir;
+
+  private StorageState state;
+  private StorageInfo storageInfo;
+
+
+  /**
+   * Determines the state of the Version file.
+   */
+  public enum StorageState {
+    NON_EXISTENT, NOT_INITIALIZED, INITIALIZED
+  }
+
+  public Storage(NodeType type, File root, String sdName)
+      throws IOException {
+    this.nodeType = type;
+    this.root = root;
+    this.storageDir = new File(root, sdName);
+    this.state = getStorageState();
+    if (state == StorageState.INITIALIZED) {
+      this.storageInfo = new StorageInfo(type, getVersionFile());
+    } else {
+      this.storageInfo = new StorageInfo(
+          nodeType, StorageInfo.newClusterID(), Time.now());
+      setNodeProperties();
+    }
+  }
+
+  /**
+   * Gets the path of the Storage dir.
+   * @return Stoarge dir path
+   */
+  public String getStorageDir() {
+    return storageDir.getAbsoluteFile().toString();
+  }
+
+  /**
+   * Gets the state of the version file.
+   * @return the state of the Version file
+   */
+  public StorageState getState() {
+    return state;
+  }
+
+  public NodeType getNodeType() {
+    return storageInfo.getNodeType();
+  }
+
+  public String getClusterID() {
+    return storageInfo.getClusterID();
+  }
+
+  public long getCreationTime() {
+    return storageInfo.getCreationTime();
+  }
+
+  public void setClusterId(String clusterId) throws IOException {
+    if (state == StorageState.INITIALIZED) {
+      throw new IOException(
+          "Storage directory " + storageDir + "already initialized.");
+    } else {
+      storageInfo.setClusterId(clusterId);
+    }
+  }
+
+  /**
+   * Retreives the storageInfo instance to read/write the common
+   * version file properties.
+   * @return the instance of the storageInfo class
+   */
+  protected StorageInfo getStorageInfo() {
+    return storageInfo;
+  }
+
+  abstract protected Properties getNodeProperties();
+
+  /**
+   * Sets the Node properties spaecific to KSM/SCM.
+   */
+  private void setNodeProperties() {
+    Properties nodeProperties = getNodeProperties();
+    if (nodeProperties != null) {
+      for (String key : nodeProperties.stringPropertyNames()) {
+        storageInfo.setProperty(key, nodeProperties.getProperty(key));
+      }
+    }
+  }
+
+  /**
+   * Directory {@code current} contains latest files defining
+   * the file system meta-data.
+   *
+   * @return the directory path
+   */
+  private File getCurrentDir() {
+    return new File(storageDir, STORAGE_DIR_CURRENT);
+  }
+
+  /**
+   * File {@code VERSION} contains the following fields:
+   * <ol>
+   * <li>node type</li>
+   * <li>KSM/SCM state creation time</li>
+   * <li>other fields specific for this node type</li>
+   * </ol>
+   * The version file is always written last during storage directory updates.
+   * The existence of the version file indicates that all other files have
+   * been successfully written in the storage directory, the storage is valid
+   * and does not need to be recovered.
+   *
+   * @return the version file path
+   */
+  private File getVersionFile() {
+    return new File(getCurrentDir(), STORAGE_FILE_VERSION);
+  }
+
+
+  /**
+   * Check to see if current/ directory is empty. This method is used
+   * before determining to format the directory.
+   * @throws IOException if unable to list files under the directory.
+   */
+  private void checkEmptyCurrent() throws IOException {
+    File currentDir = getCurrentDir();
+    if (!currentDir.exists()) {
+      // if current/ does not exist, it's safe to format it.
+      return;
+    }
+    try (DirectoryStream<Path> dirStream = Files
+        .newDirectoryStream(currentDir.toPath())) {
+      if (dirStream.iterator().hasNext()) {
+        throw new InconsistentStorageStateException(getCurrentDir(),
+            "Can't initialize the storage directory because the current "
+                + "it is not empty.");
+      }
+    }
+  }
+
+  /**
+   * Check consistency of the storage directory.
+   *
+   * @return state {@link StorageState} of the storage directory
+   * @throws IOException
+   */
+  private StorageState getStorageState() throws IOException {
+    assert root != null : "root is null";
+    String rootPath = root.getCanonicalPath();
+    try { // check that storage exists
+      if (!root.exists()) {
+        // storage directory does not exist
+        LOG.warn("Storage directory " + rootPath + " does not exist");
+        return StorageState.NON_EXISTENT;
+      }
+      // or is inaccessible
+      if (!root.isDirectory()) {
+        LOG.warn(rootPath + "is not a directory");
+        return StorageState.NON_EXISTENT;
+      }
+      if (!FileUtil.canWrite(root)) {
+        LOG.warn("Cannot access storage directory " + rootPath);
+        return StorageState.NON_EXISTENT;
+      }
+    } catch (SecurityException ex) {
+      LOG.warn("Cannot access storage directory " + rootPath, ex);
+      return StorageState.NON_EXISTENT;
+    }
+
+    // check whether current directory is valid
+    File versionFile = getVersionFile();
+    boolean hasCurrent = versionFile.exists();
+
+    if (hasCurrent) {
+      return StorageState.INITIALIZED;
+    } else {
+      checkEmptyCurrent();
+      return StorageState.NOT_INITIALIZED;
+    }
+  }
+
+  /**
+   * Creates the Version file if not present,
+   * otherwise returns with IOException.
+   * @throws IOException
+   */
+  public void initialize() throws IOException {
+    if (state == StorageState.INITIALIZED) {
+      throw new IOException("Storage directory already initialized.");
+    }
+    if (!getCurrentDir().mkdirs()) {
+      throw new IOException("Cannot create directory " + getCurrentDir());
+    }
+    storageInfo.writeTo(getVersionFile());
+  }
+
+}
+

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/common/StorageInfo.java

@@ -0,0 +1,184 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.ozone.common;
+
+import java.io.IOException;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.File;
+import java.io.RandomAccessFile;
+
+import java.util.Properties;
+import java.util.UUID;
+
+import com.google.common.base.Preconditions;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.ozone.OzoneConsts.NodeType;
+
+/**
+ * Common class for storage information. This class defines the common
+ * properties and functions to set them , write them into the version file
+ * and read them from the version file.
+ *
+ */
+@InterfaceAudience.Private
+public class StorageInfo {
+
+  private Properties properties = new Properties();
+
+  /**
+   * Property to hold node type.
+   */
+  private static final String NODE_TYPE = "nodeType";
+  /**
+   * Property to hold ID of the cluster.
+   */
+  private static final String CLUSTER_ID = "clusterID";
+  /**
+   * Property to hold creation time of the storage.
+   */
+  private static final String CREATION_TIME = "cTime";
+
+  /**
+   * Constructs StorageInfo instance.
+   * @param type
+   *          Type of the node using the storage
+   * @param cid
+   *          Cluster ID
+   * @param cT
+   *          Cluster creation Time
+
+   * @throws IOException
+   */
+  public StorageInfo(NodeType type, String cid, long cT)
+      throws IOException {
+    Preconditions.checkNotNull(type);
+    Preconditions.checkNotNull(cid);
+    Preconditions.checkNotNull(cT);
+    properties.setProperty(NODE_TYPE, type.name());
+    properties.setProperty(CLUSTER_ID, cid);
+    properties.setProperty(CREATION_TIME, String.valueOf(cT));
+  }
+
+  public StorageInfo(NodeType type, File propertiesFile)
+      throws IOException {
+    this.properties = readFrom(propertiesFile);
+    verifyNodeType(type);
+    verifyClusterId();
+    verifyCreationTime();
+  }
+
+  public NodeType getNodeType() {
+    return NodeType.valueOf(properties.getProperty(NODE_TYPE));
+  }
+
+  public String getClusterID() {
+    return properties.getProperty(CLUSTER_ID);
+  }
+
+  public Long  getCreationTime() {
+    String creationTime = properties.getProperty(CREATION_TIME);
+    if(creationTime != null) {
+      return Long.parseLong(creationTime);
+    }
+    return null;
+  }
+
+  public String getProperty(String key) {
+    return properties.getProperty(key);
+  }
+
+  public void setProperty(String key, String value) {
+    properties.setProperty(key, value);
+  }
+
+  public void setClusterId(String clusterId) {
+    properties.setProperty(CLUSTER_ID, clusterId);
+  }
+
+  private void verifyNodeType(NodeType type)
+      throws InconsistentStorageStateException {
+    NodeType nodeType = getNodeType();
+    Preconditions.checkNotNull(nodeType);
+    if(type != nodeType) {
+      throw new InconsistentStorageStateException("Expected NodeType: " + type +
+          ", but found: " + nodeType);
+    }
+  }
+
+  private void verifyClusterId()
+      throws InconsistentStorageStateException {
+    String clusterId = getClusterID();
+    Preconditions.checkNotNull(clusterId);
+    if(clusterId.isEmpty()) {
+      throw new InconsistentStorageStateException("Cluster ID not found");
+    }
+  }
+
+  private void verifyCreationTime() {
+    Long creationTime = getCreationTime();
+    Preconditions.checkNotNull(creationTime);
+  }
+
+
+  public void writeTo(File to)
+      throws IOException {
+    try (RandomAccessFile file = new RandomAccessFile(to, "rws");
+         FileOutputStream out = new FileOutputStream(file.getFD())) {
+      file.seek(0);
+    /*
+     * If server is interrupted before this line,
+     * the version file will remain unchanged.
+     */
+      properties.store(out, null);
+    /*
+     * Now the new fields are flushed to the head of the file, but file
+     * length can still be larger then required and therefore the file can
+     * contain whole or corrupted fields from its old contents in the end.
+     * If server is interrupted here and restarted later these extra fields
+     * either should not effect server behavior or should be handled
+     * by the server correctly.
+     */
+      file.setLength(out.getChannel().position());
+    }
+  }
+
+  private Properties readFrom(File from) throws IOException {
+    try (RandomAccessFile file = new RandomAccessFile(from, "rws");
+        FileInputStream in = new FileInputStream(file.getFD())) {
+      Properties props = new Properties();
+      file.seek(0);
+      props.load(in);
+      return props;
+    }
+  }
+
+  /**
+   * Generate new clusterID.
+   *
+   * clusterID is a persistent attribute of the cluster.
+   * It is generated when the cluster is created and remains the same
+   * during the life cycle of the cluster.  When a new SCM node is initialized,
+   * if this is a new cluster, a new clusterID is generated and stored.
+   * @return new clusterID
+   */
+  public static String newClusterID() {
+    return "CID-" + UUID.randomUUID().toString();
+  }
+
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/common/package-info.java

@@ -0,0 +1,18 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.apache.hadoop.ozone.common;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/scm/SCMStorage.java

@@ -0,0 +1,74 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.ozone.scm;
+
+
+import org.apache.hadoop.conf.OzoneConfiguration;
+import org.apache.hadoop.ozone.common.Storage;
+import org.apache.hadoop.ozone.OzoneConsts.NodeType;
+import org.apache.hadoop.ozone.web.utils.OzoneUtils;
+
+import java.io.IOException;
+import java.util.Properties;
+import java.util.UUID;
+
+/**
+ * SCMStorage is responsible for management of the StorageDirectories used by
+ * the SCM.
+ */
+public class SCMStorage extends Storage {
+
+  public static final String STORAGE_DIR = "scm";
+  public static final String SCM_ID = "scmUuid";
+
+  /**
+   * Construct SCMStorage.
+   * @throws IOException if any directories are inaccessible.
+   */
+  public SCMStorage(OzoneConfiguration conf) throws IOException {
+    super(NodeType.SCM, OzoneUtils.getScmMetadirPath(conf), STORAGE_DIR);
+  }
+
+  public void setScmUuid(String scmUuid) throws IOException {
+    if (getState() == StorageState.INITIALIZED) {
+      throw new IOException("SCM is already initialized.");
+    } else {
+      getStorageInfo().setProperty(SCM_ID, scmUuid);
+    }
+  }
+
+  /**
+   * Retrieves the SCM ID from the version file.
+   * @return SCM_ID
+   */
+  public String getscmUuid() {
+    return getStorageInfo().getProperty(SCM_ID);
+  }
+
+  @Override
+  protected Properties getNodeProperties() {
+    String scmUuid = getscmUuid();
+    if (scmUuid == null) {
+      scmUuid = UUID.randomUUID().toString();
+    }
+    Properties scmProperties = new Properties();
+    scmProperties.setProperty(SCM_ID, scmUuid);
+    return scmProperties;
+  }
+
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/scm/StorageContainerManager.java

@@ -35,6 +35,7 @@
 import org.apache.hadoop.conf.OzoneConfiguration;
 import org.apache.hadoop.ozone.common.DeleteBlockGroupResult;
 import org.apache.hadoop.ozone.common.BlockGroup;
+import org.apache.hadoop.ozone.common.StorageInfo;
 import org.apache.hadoop.ozone.protocol.StorageContainerDatanodeProtocol;
 import org.apache.hadoop.ozone.protocol.commands.DeleteBlocksCommand;
 import org.apache.hadoop.ozone.protocol.commands.RegisteredCommand;
@@ -82,6 +83,8 @@
 import org.apache.hadoop.scm.protocol.StorageContainerLocationProtocol;
 import org.apache.hadoop.scm.protocolPB.ScmBlockLocationProtocolPB;
 import org.apache.hadoop.scm.protocolPB.StorageContainerLocationProtocolPB;
+import org.apache.hadoop.ozone.common.Storage.StorageState;
+import org.apache.hadoop.ozone.scm.exceptions.SCMException.ResultCodes;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.util.StringUtils;
 import org.slf4j.Logger;
@@ -89,6 +92,7 @@
 
 import javax.management.ObjectName;
 import java.io.IOException;
+import java.io.PrintStream;
 import java.net.InetSocketAddress;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -100,7 +104,6 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeSet;
-import java.util.UUID;
 import java.util.Collections;
 import java.util.stream.Collectors;
 
@@ -138,12 +141,45 @@ public class StorageContainerManager extends ServiceRuntimeInfoImpl
   private static final Logger LOG =
       LoggerFactory.getLogger(StorageContainerManager.class);
 
+  /**
+   *  Startup options.
+   */
+  public enum StartupOption {
+    INIT("-init"),
+    CLUSTERID("-clusterid"),
+    GENCLUSTERID("-genclusterid"),
+    REGULAR("-regular"),
+    HELP("-help");
+
+    private final String name;
+    private String clusterId = null;
+
+    public void setClusterId(String cid) {
+      if(cid != null && !cid.isEmpty()) {
+        clusterId = cid;
+      }
+    }
+
+    public String getClusterId() {
+      return clusterId;
+    }
+
+    StartupOption(String arg) {
+      this.name = arg;
+    }
+
+    public String getName() {
+      return name;
+    }
+  }
+
   /**
    * NodeManager and container Managers for SCM.
    */
   private final NodeManager scmNodeManager;
   private final Mapping scmContainerManager;
   private final BlockManager scmBlockManager;
+  private final SCMStorage scmStorage;
 
   /** The RPC server that listens to requests from DataNodes. */
   private final RPC.Server datanodeRpcServer;
@@ -169,13 +205,18 @@ public class StorageContainerManager extends ServiceRuntimeInfoImpl
   /** SCM metrics. */
   private static SCMMetrics metrics;
 
+  private static final String USAGE =
+      "Usage: \n hdfs scm [ " + StartupOption.INIT.getName() + " [ "
+          + StartupOption.CLUSTERID.getName() + " <cid> ] ]\n " + "hdfs scm [ "
+          + StartupOption.GENCLUSTERID.getName() + " ]\n " + "hdfs scm [ "
+          + StartupOption.HELP.getName() + " ]\n";
   /**
    * Creates a new StorageContainerManager.  Configuration will be updated with
    * information on the actual listening addresses used for RPC servers.
    *
    * @param conf configuration
    */
-  public StorageContainerManager(OzoneConfiguration conf)
+  private StorageContainerManager(OzoneConfiguration conf)
       throws IOException {
 
     final int handlerCount = conf.getInt(
@@ -184,8 +225,13 @@ public StorageContainerManager(OzoneConfiguration conf)
         OZONE_SCM_DB_CACHE_SIZE_DEFAULT);
 
     StorageContainerManager.initMetrics();
-    // TODO : Fix the ClusterID generation code.
+    scmStorage = new SCMStorage(conf);
-    scmNodeManager = new SCMNodeManager(conf, UUID.randomUUID().toString());
+    String clusterId = scmStorage.getClusterID();
+    if (clusterId == null) {
+      throw new SCMException("clusterId not found",
+          ResultCodes.SCM_NOT_INITIALIZED);
+    }
+    scmNodeManager = new SCMNodeManager(conf, scmStorage.getClusterID());
     scmContainerManager = new ContainerMapping(conf, scmNodeManager, cacheSize);
     scmBlockManager = new BlockManagerImpl(conf, scmNodeManager,
         scmContainerManager, cacheSize);
@@ -321,22 +367,125 @@ private void unregisterMXBean() {
   public static void main(String[] argv) throws IOException {
     StringUtils.startupShutdownMessage(StorageContainerManager.class,
         argv, LOG);
+    OzoneConfiguration conf = new OzoneConfiguration();
     try {
-      OzoneConfiguration conf = new OzoneConfiguration();
+      StorageContainerManager scm = createSCM(argv, conf);
-      if (!DFSUtil.isOzoneEnabled(conf)) {
+      if (scm != null) {
-        System.out.println("SCM cannot be started in secure mode or when " +
+        scm.start();
-            OZONE_ENABLED + " is set to false");
+        scm.join();
-        System.exit(1);
       }
-      StorageContainerManager scm = new StorageContainerManager(conf);
-      scm.start();
-      scm.join();
     } catch (Throwable t) {
       LOG.error("Failed to start the StorageContainerManager.", t);
       terminate(1, t);
     }
   }
 
+  private static void printUsage(PrintStream out) {
+    out.println(USAGE + "\n");
+  }
+
+  public static StorageContainerManager createSCM(String[] argv,
+      OzoneConfiguration conf) throws IOException {
+    if (!DFSUtil.isOzoneEnabled(conf)) {
+      System.err.println("SCM cannot be started in secure mode or when " +
+          OZONE_ENABLED + " is set to false");
+      System.exit(1);
+    }
+    StartupOption startOpt = parseArguments(argv);
+    if (startOpt == null) {
+      printUsage(System.err);
+      terminate(1);
+      return null;
+    }
+    switch (startOpt) {
+    case INIT:
+      terminate(scmInit(conf) ? 0 : 1);
+      return null;
+    case GENCLUSTERID:
+      System.out.println("Generating new cluster id:");
+      System.out.println(StorageInfo.newClusterID());
+      terminate(0);
+      return null;
+    case HELP:
+      printUsage(System.err);
+      terminate(0);
+      return null;
+    default:
+      return new StorageContainerManager(conf);
+    }
+  }
+
+  /**
+   * Routine to set up the Version info for StorageContainerManager.
+   *
+   * @param conf OzoneConfiguration
+   * @return true if SCM initialization is successful, false otherwise.
+   * @throws IOException if init fails due to I/O error
+   */
+  public static boolean scmInit(OzoneConfiguration conf) throws IOException {
+    SCMStorage scmStorage = new SCMStorage(conf);
+    StorageState state = scmStorage.getState();
+    if (state != StorageState.INITIALIZED) {
+      try {
+        String clusterId = StartupOption.INIT.getClusterId();
+        if (clusterId != null && !clusterId.isEmpty()) {
+          scmStorage.setClusterId(clusterId);
+        }
+        scmStorage.initialize();
+        System.out.println("SCM initialization succeeded." +
+            "Current cluster id for sd=" + scmStorage.getStorageDir() + ";cid="
+                + scmStorage.getClusterID());
+        return true;
+      } catch (IOException ioe) {
+        LOG.error("Could not initialize SCM version file", ioe);
+        return false;
+      }
+    } else {
+      System.out.println("SCM already initialized. Reusing existing" +
+          " cluster id for sd=" + scmStorage.getStorageDir() + ";cid="
+              + scmStorage.getClusterID());
+      return true;
+    }
+  }
+
+  private static StartupOption parseArguments(String[] args) {
+    int argsLen = (args == null) ? 0 : args.length;
+    StartupOption startOpt = StartupOption.HELP;
+    if (argsLen == 0) {
+      startOpt = StartupOption.REGULAR;
+    }
+    for (int i = 0; i < argsLen; i++) {
+      String cmd = args[i];
+      if (StartupOption.INIT.getName().equalsIgnoreCase(cmd)) {
+        startOpt = StartupOption.INIT;
+        if (argsLen > 3) {
+          return null;
+        }
+        for (i = i + 1; i < argsLen; i++) {
+          if (args[i].equalsIgnoreCase(StartupOption.CLUSTERID.getName())) {
+            i++;
+            if (i < argsLen && !args[i].isEmpty()) {
+              startOpt.setClusterId(args[i]);
+            } else {
+              // if no cluster id specified or is empty string, return null
+              LOG.error("Must specify a valid cluster ID after the "
+                  + StartupOption.CLUSTERID.getName() + " flag");
+              return null;
+            }
+          } else {
+            return null;
+          }
+        }
+      } else if (StartupOption.GENCLUSTERID.getName().equalsIgnoreCase(cmd)) {
+        if (argsLen > 1) {
+          return null;
+        }
+        startOpt = StartupOption.GENCLUSTERID;
+      }
+    }
+    return startOpt;
+  }
+
   /**
    * Returns a SCMCommandRepose from the SCM Command.
    * @param cmd - Cmd

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/scm/exceptions/SCMException.java

@@ -113,6 +113,7 @@ public enum ResultCodes {
     BLOCK_EXISTS,
     FAILED_TO_FIND_BLOCK,
     IO_EXCEPTION,
-    UNEXPECTED_CONTAINER_STATE
+    UNEXPECTED_CONTAINER_STATE,
+    SCM_NOT_INITIALIZED
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/ozone/MiniOzoneCluster.java

@@ -38,6 +38,7 @@
 import org.apache.hadoop.ozone.ksm.protocolPB
     .KeySpaceManagerProtocolClientSideTranslatorPB;
 import org.apache.hadoop.ozone.ksm.protocolPB.KeySpaceManagerProtocolPB;
+import org.apache.hadoop.ozone.scm.SCMStorage;
 import org.apache.hadoop.ozone.web.client.OzoneRestClient;
 import org.apache.hadoop.scm.ScmConfigKeys;
 import org.apache.hadoop.scm.protocolPB
@@ -458,6 +459,7 @@ public MiniOzoneCluster build() throws IOException {
       configureTrace();
       configureSCMheartbeat();
       configScmMetadata();
+      configVersionFile();
 
       conf.set(ScmConfigKeys.OZONE_SCM_CLIENT_ADDRESS_KEY, "127.0.0.1:0");
       conf.set(ScmConfigKeys.OZONE_SCM_BLOCK_CLIENT_ADDRESS_KEY, "127.0.0.1:0");
@@ -475,7 +477,8 @@ public MiniOzoneCluster build() throws IOException {
       conf.setBoolean(OzoneConfigKeys.DFS_CONTAINER_IPC_RANDOM_PORT,
           randomContainerPort);
 
-      StorageContainerManager scm = new StorageContainerManager(conf);
+      StorageContainerManager scm =
+          StorageContainerManager.createSCM(null, conf);
       scm.start();
 
       KeySpaceManager ksm = new KeySpaceManager(conf);
@@ -528,6 +531,12 @@ private void configScmMetadata() throws IOException {
           scmPath.toString() + "/datanode.id");
     }
 
+    private void configVersionFile() throws IOException {
+      SCMStorage scmStore = new SCMStorage(conf);
+      scmStore.setClusterId(runID.toString());
+      scmStore.initialize();
+    }
+
     private void configureHandler() {
       conf.setBoolean(OzoneConfigKeys.OZONE_ENABLED, this.ozoneEnabled);
       if (!ozoneHandlerType.isPresent()) {

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/ozone/TestStorageContainerManager.java

@@ -29,7 +29,9 @@
 import org.apache.hadoop.ozone.protocol.proto.StorageContainerDatanodeProtocolProtos.DeletedBlocksTransaction;
 import org.apache.hadoop.ozone.protocol.proto.StorageContainerDatanodeProtocolProtos.ReportState;
 import org.apache.hadoop.ozone.protocol.proto.StorageContainerDatanodeProtocolProtos.Type;
+import org.apache.hadoop.ozone.scm.SCMStorage;
 import org.apache.hadoop.ozone.scm.StorageContainerManager;
+import org.apache.hadoop.ozone.scm.StorageContainerManager.StartupOption;
 import org.apache.hadoop.ozone.scm.block.DeletedBlockLog;
 import org.apache.hadoop.ozone.scm.block.SCMBlockDeletingService;
 import org.apache.hadoop.ozone.scm.node.NodeManager;
@@ -39,11 +41,15 @@
 import org.junit.Assert;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.List;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.Map;
 import java.util.Collections;
+import java.util.UUID;
 
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
@@ -349,4 +355,45 @@ private Map<String, List<String>> createDeleteTXLog(DeletedBlockLog delLog,
 
     return containerBlocks;
   }
+
+  @Test
+  public void testSCMInitialization() throws Exception {
+    OzoneConfiguration conf = new OzoneConfiguration();
+    final String path = GenericTestUtils.getTempPath(
+        UUID.randomUUID().toString());
+    Path scmPath = Paths.get(path, "scm-meta");
+    conf.set(OzoneConfigKeys.OZONE_METADATA_DIRS, scmPath.toString());
+
+    StartupOption.INIT.setClusterId("testClusterId");
+    // This will initialize SCM
+    StorageContainerManager.scmInit(conf);
+
+    SCMStorage scmStore = new SCMStorage(conf);
+    Assert.assertEquals(OzoneConsts.NodeType.SCM, scmStore.getNodeType());
+    Assert.assertEquals("testClusterId", scmStore.getClusterID());
+    StartupOption.INIT.setClusterId("testClusterIdNew");
+    StorageContainerManager.scmInit(conf);
+    Assert.assertEquals(OzoneConsts.NodeType.SCM, scmStore.getNodeType());
+    Assert.assertEquals("testClusterId", scmStore.getClusterID());
+
+  }
+
+  @Test
+  public void testSCMReinitialization() throws Exception {
+    OzoneConfiguration conf = new OzoneConfiguration();
+    final String path = GenericTestUtils.getTempPath(
+        UUID.randomUUID().toString());
+    Path scmPath = Paths.get(path, "scm-meta");
+    conf.set(OzoneConfigKeys.OZONE_METADATA_DIRS, scmPath.toString());
+    //This will set the cluster id in the version file
+    MiniOzoneCluster cluster =
+        new MiniOzoneCluster.Builder(conf).numDataNodes(1)
+            .setHandlerType(OzoneConsts.OZONE_HANDLER_DISTRIBUTED).build();
+    StartupOption.INIT.setClusterId("testClusterId");
+    // This will initialize SCM
+    StorageContainerManager.scmInit(conf);
+    SCMStorage scmStore = new SCMStorage(conf);
+    Assert.assertEquals(OzoneConsts.NodeType.SCM, scmStore.getNodeType());
+    Assert.assertNotEquals("testClusterId", scmStore.getClusterID());
+  }
 }