HDFS - Snapshot

Snapshots support storing a copy of data at a particular instant of time. One usage of the snapshot feature may be to roll back a corrupted HDFS instance to a previously known good point in time.

See HDFS - Fs Shell

See HDFS - DFSAdmin option -allowSnapshot <snapshotDir> : Allow snapshots to be taken on a directory.

See HDFS - DFSAdmin option -disallowSnapshot <snapshotDir> : Do not allow snapshots to be taken on a directory any more.

HDFS - hdfs command line diff sub-command make a diff of two snapshots of a directory or diff the current directory contents with a snapshot

hdfs snapshotDiff         

list all snapshottable dirs owned by the current user

hdfs lsSnapshottableDir   

• http://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-hdfs/HdfsSnapshots.html