面试题与答案

Hadoop is a distributed computing platform. It is written in Java. It consists of the features like Google File System and MapReduce.

Java 1.6.x or higher versions are good for Hadoop, preferably from Sun. Linux and Windows are the supported operating system for Hadoop, but BSD, Mac OS/X, and Solaris are more famous for working.

Hadoop can run on a dual processor/ dual core machines with 4-8 GB RAM using ECC memory. It depends on the workflow needs.

These are the most common input formats defined in Hadoop:

1. TextInputFormat
2. KeyValueInputFormat
3. SequenceFileInputFormat

TextInputFormat is a by default input format.

The big data can be categorized using the following features:

• Volume
• Velocity
• Variety

We use panels in bootstrap from the boxing of DOM components.

Button groups are used for the placement of more than one buttons in the same line.

• Ordered list
• Unordered list
• Definition list

The 'jps' command is used for the retrieval of the status of daemons running the Hadoop cluster.

When a Hadoop job runs, it splits input files into chunks and assigns each split to a mapper for processing. It is called the InputSplit.

In TextInputFormat, each line in the text file is a record. Value is the content of the line while Key is the byte offset of the line. For instance, Key: longWritable, Value: text