Question 1

Given:  You want to clean up this list by removing jobs where the State is KILLED. What command you enter?
A) Yarn application -refreshJobHistory
B) Yarn application -kill application_1374638600275_0109
C) Yarn rmadmin -refreshQueue
D) Yarn rmadmin -kill application_1374638600275_0109

Accepted Answer

The answer of Given:  You want to clean up...

Question 2

Assume you have a file named foo.txt in your local directory. You issue the following three commands: Hadoop fs -mkdir input Hadoop fs -put foo.txt input/foo.txt Hadoop fs -put foo.txt input What happens when you issue the third command?
A) The write succeeds, overwriting foo.txt in HDFS with no warning
B) The file is uploaded and stored as a plain file named input
C) You get a warning that foo.txt is being overwritten
D) You get an error message telling you that foo.txt already exists, and asking you if you would like to overwrite it.
E) You get a error message telling you that foo.txt already exists. The file is not written to HDFS
F) You get an error message telling you that input is not a directory
G) The write silently fails

Accepted Answer

The answer of Assume you have a file named foo.txt...

Question 3

You have recently converted your Hadoop cluster from a MapReduce 1 (MRv1) architecture to MapReduce 2 (MRv2) on YARN architecture. Your developers are accustomed to specifying map and reduce tasks (resource allocation) tasks when they run jobs: A developer wants to know how specify to reduce tasks when a specific job runs. Which method should you tell that developers to implement?
A) MapReduce version 2 (MRv2) on YARN abstracts resource allocation away from the idea of "tasks" into memory and virtual cores, thus eliminating the need for a developer to specify the number of reduce tasks, and indeed preventing the developer from specifying the number of reduce tasks.
B) In YARN, resource allocations is a function of megabytes of memory in multiples of 1024mb. Thus, they should specify the amount of memory resource they need by executing -D mapreduce-reduces.memory-mb-2048
C) In YARN, the ApplicationMaster is responsible for requesting the resource required for a specific launch. Thus, executing -D yarn.applicationmaster.reduce.tasks=2 will specify that the ApplicationMaster launch two task contains on the worker nodes.
D) Developers specify reduce tasks in the exact same way for both MapReduce version 1 (MRv1) and MapReduce version 2 (MRv2) on YARN. Thus, executing -D mapreduce.job.reduces-2 will specify reduce tasks.
E) In YARN, resource allocation is function of virtual cores specified by the ApplicationManager making requests to the NodeManager where a reduce task is handeled by a single container (and thus a single virtual core). Thus, the developer needs to specify the number of virtual cores to the NodeManager by executing -p yarn.nodemanager.cpu-vcores=2

Accepted Answer

In both MRv1 and MRv2 on YARN, developers specify the number of reduce tasks using the same configuration property: `-D mapreduce.job.reduces=2`.

Question 4

Choose three reasons why should you run the HDFS balancer periodically? (Choose three)
A) To ensure that there is capacity in HDFS for additional data
B) To ensure that all blocks in the cluster are 128MB in size
C) To help HDFS deliver consistent performance under heavy loads
D) To ensure that there is consistent disk utilization across the DataNodes
E) To improve data locality MapReduce

Accepted Answer

The answer of Choose three reasons why should you run...

Question 5

You have a cluster running with a FIFO scheduler enabled. You submit a large job A to the cluster, which you expect to run for one hour. Then, you submit job B to the cluster, which you expect to run a couple of minutes only. You submit both jobs with the same priority. Which two best describes how FIFO Scheduler arbitrates the cluster resources for job and its tasks? (Choose two)
A) Because there is a more than a single job on the cluster, the FIFO Scheduler will enforce a limit on the percentage of resources allocated to a particular job at any given time
B) Tasks are scheduled on the order of their job submission
C) The order of execution of job may vary
D) Given job A and submitted in that order, all tasks from job A are guaranteed to finish before all tasks from job B
E) The FIFO Scheduler will give, on average, and equal share of the cluster resources over the job lifecycle
F) The FIFO Scheduler will pass an exception back to the client when Job B is submitted, since all slots on the cluster are use

Accepted Answer

The answer of You have a cluster running with a...

Question 6

In CDH4 and later, which file contains a serialized form of all the directory and files inodes in the filesystem, giving the NameNode a persistent checkpoint of the filesystem metadata?
A) fstime
B) VERSION
C) Fsimage_N (where N reflects transactions up to transaction ID N)
D) Edits_N-M (where N-M transactions between transaction ID N and transaction ID N)

Accepted Answer

The Fsimage_N file contains a serialized form of all the directory and file inodes in the filesystem, providing a persistent checkpoint of the filesystem metadata for the NameNode.

Question 7

You have just run a MapReduce job to filter user messages to only those of a selected geographical region. The output for this job is in a directory named westUsers, located just below your home directory in HDFS. Which command gathers these into a single file on your local file system?
A) Hadoop fs -getmerge -R westUsers.txt
B) Hadoop fs -getemerge westUsers westUsers.txt
C) Hadoop fs -cp westUsers/* westUsers.txt
D) Hadoop fs -get westUsers westUsers.txt

Accepted Answer

The correct command is "Hadoop fs -getmerge westUsers westUsers.txt" which merges files from the HDFS directory into a single file on the local file system.

Question 8

You are running  Hadoop cluster with all monitoring facilities properly configured. Which scenario will go undeselected?
A) HDFS is almost full
B) The NameNode goes down
C) A DataNode is disconnected from the cluster
D) Map or reduce tasks that are stuck in an infinite loop
E) MapReduce jobs are causing excessive memory swaps

Accepted Answer

The answer of You are running  Hadoop cluster with all monitoring...

Question 9

Your cluster implements HDFS High Availability (HA). Your two NameNodes are named nn01 and nn02. What occurs when you execute the command: hdfs haadmin -failover nn01 nn02?
A) nn02 is fenced, and nn01 becomes the active NameNode
B) nn01 is fenced, and nn02 becomes the active NameNode
C) nn01 becomes the standby NameNode and nn02 becomes the active NameNode
D) nn02 becomes the standby NameNode and nn01 becomes the active NameNode

Accepted Answer

The answer of Your cluster implements HDFS High Availability (HA)....

Question 10

You have installed a cluster HDFS and MapReduce version 2 (MRv2) on YARN. You have no dfs.hosts entry(ies) in your hdfs-site.xml configuration file. You configure a new worker node by setting fs.default.name in its configuration files to point to the NameNode on your cluster, and you start the DataNode daemon on that worker node. What do you have to do on the cluster to allow the worker node to join, and start sorting HDFS blocks?
A) Without creating a dfs.hosts file or making any entries, run the commands hadoop.dfsadmin-refreshModes on the NameNode
B) Restart the NameNode
C) Creating a dfs.hosts file on the NameNode, add the worker Node's name to it, then issue the command hadoop dfsadmin -refresh Nodes = on the Namenode
D) Nothing; the worker node will automatically join the cluster when NameNode daemon is started

Accepted Answer

The correct answer is A because the command hadoop dfsadmin -refreshNodes on the NameNode will allow the worker node to join the cluster and start sorting HDFS blocks.

Exam 1: Cloudera Certified Administrator for Apache Hadoop (CCAH)

Given: 11ec3bb2_d99c_4fb7_916b_074cfa3d65b6__00 You want to clean up this list by removing jobs where the State is KILLED. What command you enter?

Assume you have a file named foo.txt in your local directory. You issue the following three commands: Hadoop fs -mkdir input Hadoop fs -put foo.txt input/foo.txt Hadoop fs -put foo.txt input What happens when you issue the third command?

Choose three reasons why should you run the HDFS balancer periodically? (Choose three)

In CDH4 and later, which file contains a serialized form of all the directory and files inodes in the filesystem, giving the NameNode a persistent checkpoint of the filesystem metadata?

You have just run a MapReduce job to filter user messages to only those of a selected geographical region. The output for this job is in a directory named westUsers, located just below your home directory in HDFS. Which command gathers these into a single file on your local file system?

You are running Hadoop cluster with all monitoring facilities properly configured. Which scenario will go undeselected?

Your cluster implements HDFS High Availability (HA) . Your two NameNodes are named nn01 and nn02. What occurs when you execute the command: hdfs haadmin -failover nn01 nn02?