Q1. 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
Correct Answer: B
Q2. 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)
Correct Answer: C
Q3. You are running a Hadoop cluster with a NameNode on host mynamenode. What are two ways to determine available HDFS space in your cluster?
A.Run hdfs fs --du / and locate the DFS Remaining value
B. Run hdfs dfsadmin --report and locate the DFS Remaining value
C. Run hdfs dfs / and subtract NDFS Used from configured Capacity
D. Connect to http://mynamenode:50070/dfshealth.jsp and locate the DFS remaining value
Correct Answer: C, D
Q4. 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 mapreducereduces. 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
Correct Answer: D
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