1、Hadoop Several modes of operation ？
Hadoop The operation mode includes ： Local mode 、 Pseudo distributed mode 、 Fully distributed mode
2、SCP Command to use
Secure copy , It can copy data between servers
3、rsync Command to use
Remote synchronization tool . Mainly used for backup and mirroring . Fast speed 、 Advantages of avoiding the same content and supporting symbolic links .
use rsync Make a copy of the file than scp Fast ,rsync Only update the difference file ,scp It's copying all the files .
5、DataNode and NameNode Processes can only work one at a time , Investigation plan .
First jps Command to check , The problem may be that the formatting is not turned off DataNode, Then close it DataNode and NameNode
then , Delete the generated data Contents and logs Catalog , Finally, execute the format command again