Learning Notes-Security Mode and Directory Snapshots for hadoop

Safety mode

1. When namenode starts, merge p_w_picpath and edit to form a new p_w_picpath and generate a new edit log.

2. In the whole intelligent safe mode, the client can only read

3. Check whether nameode is in safe mode.

Hdfs dfsadmin-safemode get / / View security mode

Hdfs dfsadmin-safemode enter / / enter safe mode

Hdfs dfsadmin-safemode leave / / leave safe mode

Hdfs dfsadmin-safemode wait / / wait security mode

4. Save the namespace manually: dfsadmin-saveNamespace

5. Save the image file manually: hdfs dfsadmin-fetchImage

6. Save metadata: (save it under hadoop_home: hadoop / logs/) hdfs dfsadmin-metasave xxx.dsds

7. Start-balancer.sh: start the equalizer to make the data storage of the cluster more average and improve the performance of the entire cluster. (generally speaking, we are adding sections

Start the equalizer only when you click)

8. Hadoop fs-count Statistical Catalog

Hadoop Snapshot snapshot: is to take a picture of the current situation and save it. Snapshots cannot be created by default in general directories. Hdfs must be performed

Dfsadmin-allowSnapshot / user/ubuntu/data. Allows you to create a snapshot, followed by the address path where you want to create the snapshot. It is allowed here

After creating the snapshot, we can execute adoop fs-createSnapshot / user/ubuntu/data snap-1 to create the snapshot. Snap-1 is what you create quickly.

By name. To view snapshots, go directly to hadoop fs-ls-R / user/ubuntu/data/.snapshot/. And you can't stop it when you create a snapshot.

With a snapshot.

1. Create a snapshot hadoop fs [- createSnapshot []]

2. Delete snapshot hadoop fs [- deleteSnapshot]

3. Rename snapshot hadoop fs [- renameSnappshot]

4. Allow directory snapshots hadoop dfsadmin [- allowSnapshot]

5. Disable directory snapshot hadoop dfsamdin [- disallowSnapshot]