I am new to hadoop and recently when I was running MapReduce jobs on Openstack hadoop cluster and cd into directory on a datanode machine, I found there are two hadoop folders one is called "hadoop" while the other named"hadoop-2.7.1". Obviously, the latter one makes more sense as it tells the hadoop version. The two folder contains same sub-directories, but how these two differ from each other? What if I'd like to disable HDFS permission checking on this machine, which one should I go?
Here is a screenshot
As colors in the screenshot suggest, hadoop is not a separate directory but is just a symbolic link, obviously pointing to hadoop-2.7.1. Run ls -l to check this.
You should cd into hadoop directory. It exists intentionally to avoid writing hadoop version explicitly. When new version of hadoop is deployed, a new versioned directory will be created, and hadoop symbolic link will be changed to point to the latest versioned directory. Like this:
hadoop-2.7.1
hadoop-2.7.2
hadoop-2.7.3
hadoop -> hadoop-2.7.3
Related
I am new to Hadoop and am trying to execute the WordCount Problem.
Things I did so far -
Setting up the Hadoop Single Node cluster referring the below link.
http://www.bogotobogo.com/Hadoop/BigData_hadoop_Install_on_ubuntu_single_node_cluster.php
Write the word count problem referring the below link
https://kishorer.in/2014/10/22/running-a-wordcount-mapreduce-example-in-hadoop-2-4-1-single-node-cluster-in-ubuntu-14-04-64-bit/
Problem is when I execute the last line to run the program -
hadoop jar wordcount.jar /usr/local/hadoop/input /usr/local/hadoop/output
Following is the error I get -
The directory seems to be present
The file is also present in the directory with contents
Finally, on a side note I also tried the following directory sturcture in the jar command.
No avail! :/
I would really appreciate if someone could guide me here!
Regards,
Paul Alwin
Your first image is using input from the local Hadoop installation directory, /usr
If you want to use that data on your local filesystem, you can specify file:///usr/...
Otherwise, if you're running pseudo distributed mode, HDFS has been setup, and /usr does not exist in HDFS unless you explicitly created it there.
Based on the stacktrace, I believe the error comes from the /app/hadoop/ staging directory path not existing, or the permissions for it are not allowing your current user to run commands against that path
Suggestion: Hortonworks and Cloudera offer pre-built VirtualBox images and lots of tutorial resources. Most companies will have Hadoop from one of those vendors, so it's better to get familiar with that rather than mess around with having to install Hadoop yourself from scratch, in my opinion
I've searched and I've been reading on Cloudera Hadoop on removing mount point file systems but I cannot find a thing on removing them.
I have two SSD drives in 6 machines and when I initially installed Cloudera Hadoop it added all file systems and I only need two mount points to run a few teragen and terasorts.
I need to remove everything except for:
/dev/nvme0n1 and /dev/nvme1n1
In Cloudera Manager you can modify the list of drives used for HDFS data at:
Clusters > HDFS > Configuration > DataNode Default Group (or whatever you may have renamed this to) > DataNode Data Directory
I was going through the HADOOP fs commands list. I am little perplexed not to find any "cd" command in hadoop fs.
Why is it so? It might sound silly question for the HADOOP users, but as I am beginner I can not understand why there is no list of cd command in HADOOP fs level?
Think about it like this:
Hadoop has a special file system called "hdfs" which runs on top of existing say linux file system. There is no concept of current or present working directory a.k.a. pwd
Let's say we have following structure in hdfs:
d1/
d2/
f1
d3/
f2
d4/
f3
You could do cd in your Linux file system from moving from one to the other but do you think changing directory in hadoop would makes sense? HDFS is like virtual file system and you dont directly interact with hdfs except via hadoop command or job tracker.
HDFS provides various features that enable accessing HDFS(Hadoop Filesystem) easy on local machines or edge nodes. You have an option to mount HDFS using any of the following methods. Once Hadoop file system is mounted on your machine, you may use cd command to browse through the file system (It's is like mounting remote network filesystem like NAS)
Fuse dfs (Available from Hadoop 0.20 onwards )
NFSv3 Gateway access to HDFS data (Available from Hadoop version
Hadoop 2.2.0)
Hi I am trying to run hadoop on a server that has hadoop installed but I have no idea the directory where hadoop resides. The server was configure by the server admin.
In order to load hadoop I use the use command from the dotkit package.
There may be several solutions but wanted to know where the hadoop package was installed, how to set up the $HADOOP_HOME variable, and how to approp run a hadoop streaming job, such as $HADOOP_HOME/bin/hadoop jar $HADOOP_HOME/mapred/contrib/streaming/hadoop-streaming.jar, aka, http://wiki.apache.org/hadoop/HadoopStreaming.
Thanks! any help would be greatly appreciated!
If you're using a cloudera distribution then it's most probably in /usr/lib/hadoop, otherwise it could be anywhere (at the discretion of your system admin).
There are some tricks you can use to try and locate it:
locate hadoop-env.sh (assuming that locate has been installed and updatedb has been run recently)
If the machine you're running this on is running a hadoop service (such as data node, job tracker, task tracker, name node), then you can perform a process list and grep for the hadoop command: ps axww | grep hadoop
Failing the above two, look for the hadoop root directory in some common locations such as: /usr/lib, /usr/local, /opt
Failing all this, and assuming your current user has the permissions: find / -name hadoop-env.sh
If you're install with rpm then it's most probably in /etc/hadoop.
Why don't you try:
echo $HADOOP_HOME
Obiviously the above env variable has to be set before you could even issue hadoop executables from anywhere on the box.
I had installed hadoop stable version successfully. but confused while installing hadoop -2.0.0 version.
I want to install hadoop-2.0.0-alpha on two nodes, using federation on both machines. rsi-1, rsi-2 are hostnames.
what should be values of below properties for implementation of federation. Both machines are also used for datanodes too.
fs.defaulFS dfs.federation.nameservices dfs.namenode.name.dir dfs.datanode.data.dir yarn.nodemanager.localizer.address yarn.resourcemanager.resource-tracker.address yarn.resourcemanager.scheduler.address yarn.resourcemanager.address
One more point, in stable version of hadoop i have configuration files under conf folder in installation directory.
But in 2.0.0-aplha version, there is etc/hadoop directory and it doesnt have mapred-site.xml, hadoop-env.sh. do i need to copy conf folder under share folder into hadoop-home directory? or do i need to copy these files from share folder into etc/hadoop directory?
Regards, Rashmi
You can run hadoop-setup-conf.sh in sbin folder. It instructs you step-by-step to configure.
Please remember when it asks you to input the directory path, you should use full link
e.g., when it asks for conf directory, you should input /home/user/Documents/hadoop-2.0.0/etc/hadoop
After completed, remember to check every configuration file in etc/hadoop.
As my experience, I modified JAVA_HOME variable in hadoop-env.sh and some properties in core-site.xml, mapred-site.xml.
Regards