Need explanation on Hadoop file system - hadoop

Question

For the following command,
hadoop fs -put foo.txt bar.txt
After the operation succeeds, where will bar.txt locate in my local hard drive, given
a singe node setup?
pseudo distributed setup?
Will bar.txt still get replicated 3 times for backup?

Answer 1

bar.txt will be placed in the current hadoop user home directory as
/user/<hadoop-user> as per the following code
#Override
public Path getHomeDirectory() {
return makeQualified(new Path("/user/" + dfs.ugi.getShortUserName()));
}
Source here
If the cluster is single node, It only replicates one time even you set the dfs.replication to 3 because Hadoop will not save the same block on same node more than once.
pseudo distributed mode will have all the hadoop daemons running on the same machine. It's nothing but single node cluster.
It you set dfs.replication to 3, Hadoop just gives you warning only.
Hope it helps!

Answer 2

the above fs command tries to put the file foo.txt as bar.txt in current hdfs. The path of the hdfs is determined by the current user the operation is performing. This is because you are not providing the absolute path to the destination.
If you have /user as the home directory configured in hdfs, it will take the path of /user/ and places the file there.
Also, if there is no folder in hdfs that corresponds to the current user it will fail stating file doesn't exists.
e.g. Current user running is "testusr1". and the above command places the file under "/users/testusr1" .
You can verify this by executing a command #hadoop fs -ls /user/
AFAIK this will be should be same for Pseudo or single node setup.
[root#sandbox ~]# hadoop fs -ls /user
Found 11 items
drwx------ - root hdfs 0 2015-04-13 03:59 /user/root
.
.
.
.
.
drwxr-xr-x - root hdfs 0 2015-04-13 04:18 /user/testusr1
[root#sandbox ~]#
[root#sandbox ~]# su - testusr1
[testusr1#sandbox ~]$ whoami
testusr1
[testusr1#sandbox ~]$ pwd
/home/testusr1
[testusr1#sandbox ~]$ ll
total 7
-rw-rw-r-- 1 testusr1 testusr1 49 2015-04-13 04:17 foo-testusr2.txt
[testusr1#sandbox ~]$ hadoop fs -put foo-testusr2.txt bar-testusr2.txt
And for the replication factor, you can check with he help of basic hadoop fs -ls command.
[testusr1#sandbox ~]$exit
logout
[root#sandbox ~]# hdfs dfs -ls /user/testusr1
Found 1 items
-rw-r--r-- 1 testusr1 hdfs 49 2015-04-13 04:18 /user/testusr1/bar-testusr2.txt
[root#sandbox ~]#
In the above sample output, you can see the number 1 right after the file permissions. It is reflecting as 1 and it is as per my hdfs configurations.