Apache Hadoop is opensource framework for Storage & Processing purpose. For Storage purpose HDFS(Hadoop Distributed File System) and for Processing purpose(Map Reduce) using. Here is some Hadoop admin commands for beginners.
Hadoop Admin Commands:
hadoop namenode -format:
In this command explain about format HDFS file system from Nam node in a cluster.
hadoop dfsadmin -report :
In this command showing report on the overall HDFS file system. This command very useful for how much disk is available , Name node information, how many Data Nodes are running and corrupted blocks are in a cluster.
hadoop dfsadmin -refreshNodes:
This commands used commission or decommission nodes
Safe mode commands in Hadoop:
It is a state of Name node, does not allow changes to the file system and Read-only mode for the Hadoop cluster. Mostly three commands are related to safe mode.
hadoop dfadmin -safemode get:
safemode get means that get status of the safe mode(maintenance mode)
hadoop dfadmin -safemode enter:
In this command exactly meaning that Safe mode is ON.
hadoop dfsadmin -safemode leave:
Leave command means that Safe mode is OFF.
start-all.sh:
Start the all daemons like name node, secondary name node, yarn, data nodes, node manager etc.
stop-all.sh:
Stop the all daemons like name node, data node, secondary name node, resource manager, node manager, yarn etc.
hadoop fs -copyFromLocal <file 1> <file 2> :
In hadoop environment we need to copy files from local file system to HDFS use this command
hadoop fs -copyToLocal< file 1> <file2> :
Copy files HDFS to local file system in a hadoop cluster
hadoop fs -put <file 1> <file 2> :
This command same like as copyFromLocal but small difference is remote location to HDFS
hadoop fs -get <file 1 > <file 2> :
This command same like as copyToLocal but small difference is HDFS to remote location.
hadoop fs -setrep -w 5 file:
For set a replication factor manually using below command
hadoop distcp hdfs://<ip1>/input hdfs://<ip2>/output :
For copy file one cluster to another cluster using below command
hadoop job -status <job -id >:
To check hadoop jobs status we use this command.
hadoop job -submit <job – files > :
To submit hadoop job file using this command.
hadoop job -list all :
You want to hadoop jobs so will use this command simply.
hadoop job -kill-task < task – id>:
In hadoop jobs we need to urgently kill the task in processing time. At the time this command is more useful