hdfs commands

The architecture of HDFS adopts the masterslave mode. an HDFS cluster consists of one Namenode and multiple Datanode. In an HDFS cluster, there is only one Namenode node. As the central server of the HDFS cluster, Namenode is mainly responsible for: 1. Managing the Namespace of the file system in the

What is 1.HDFS?The Hadoop Distributed File System (HDFS) is designed to be suitable for distributed file systems running on general-purpose hardware (commodity hardware). It has a lot in common with existing Distributed file systems.Basic Concepts in 2.HDFS(1) blocks (block)"Block" is a fixed-size storage unit, HDFS fi

User identityIn 1.0.4 This version of Hadoop, the client user identity is given through the host operating system. For Unix-like systems, User name equals ' WhoAmI '; The list of groups equals ' bash-c groups '. In the future there will be additional ways to determine user identities (such as Kerberos, LDAP, etc.). It is unrealistic to expect to use the first approach mentioned above to prevent a user from impersonating another user. This user identification mechanism, combin

Enable backup of files on HDFs via snapshotAPI address please see http://archive.cloudera.com/cdh5/cdh/5/hadoop-2.5.0-cdh5.2.0/hadoop-project-dist/hadoop-hdfs/HdfsSnapshots.html==========================================================================================1. Allow snapshot creationFirst, execute the command below the folder where you want to make the backup, allowing the folder to create a snapsh

core of Hadoop is HDFs and MapReduce, and both are theoretical foundations, not specific, high-level applications, and Hadoop has a number of classic sub-projects, such as HBase, Hive, which are developed based on HDFs and MapReduce. To understand Hadoop, you have to know what HDFs and MapReduce are. Hdfs

It is finally here: you can configure the Open Source log-aggregator, scribe, to log data directly into the hadoop distributed file system. Compile Web 2.0 companies have to deploy a bunch of costly filers to capture weblogs being generated by their application. currently, there is no option other than a costly filer because the write-rate for this stream is huge. the hadoop-scribe integration allows this write-load to be distributed among a bunch of commodity machines, thus cing the total cost

This article uses the hadoop Source Code. For details about how to import the hadoop source code to eclipse, refer to the first phase. I. background of HDFS As the amount of data increases, the data cannot be stored within the jurisdiction of an operating system, so it is allocated to more disks managed by the operating system, but it is not convenient to manage and maintain, A distributed file management system is urgently needed to manage files on

Hadoop HDFS clusters are prone to unbalanced disk utilization between machines, such as adding new data nodes to clusters. When HDFS is unbalanced, many problems will occur, such as Mr.ProgramThe advantages of local computing cannot be well utilized, the network bandwidth usage between machines cannot be better, and the machine disk cannot be used. It can be seen that it is very important to ensure data bal

Sqoop Flume Hdfs Sqoop is used to import data from a structured data source, such as an RDBMS Flume for moving bulk stream data to HDFs HDFs Distributed File system for storing data using the Hadoop ecosystem The Sqoop has a connector architecture. The connector knows how to connect to the appropriate data source

Environment: Eclipse + Eclipse Hadoop plugin, Hadoop + rhel6.4Package Test;import Java.io.ioexception;import Java.net.uri;import org.apache.hadoop.conf.configuration;import Org.apache.hadoop.fs.filesystem;import Org.apache.hadoop.fs.Path; Import Org.apache.hadoop.fs.fsdatainputstream;import org.apache.hadoop.fs.FSDataOutputStream;; public class Test {public void WriteFile (String HDFs) throws IOException {Configuration conf = new configuration (); Fil

Configuration file m103 Replace with the HDFs service address.To use the Java client to access the file on the HDFs, have to say is the configuration file Hadoop-0.20.2/conf/core-site.xml, originally I was here to eat a big loss, so I am not even hdfs, file can not be created, read. Configuration item: Hadoop.tmp.dir represents the directory locati

Continue the previous chapter to organize the HDFs related configuration items Name Value Description Dfs.default.chunk.view.size 32768 The content display size for each file in the HTTP access page of Namenode, usually without setting. Dfs.datanode.du.reserved 1073741824 The amount of space reserved for each disk needs to be set up, mainly for non-HDFS