How jobs are copied to other nodes?

[Ben Kucinich]

I am interested to know the internal working of Hadoop regarding
distribution of jobs. How are the jobs copied to other nodes?

Is the class file copied to all other nodes where they are executed?

URLs contain non-existant domain names in machines.jsp

[Ben Kucinich]

I have a Hadoop running on a master node 192.168.1.8. fs.default.name
is 192.168.101.8:9000 and mapred.job.tracker is 192.168.101.8:9001.

I am accessing it's web pages on port 50030 from another machine. I
visited http://192.168.101.8:50030/machines.jsp. It showed:-

NameHost# running tasks FailuresSeconds since heartbeat
tracker_hadoop.domain.example.com:/127.0.0.1:4545   
hadoop.domain.example.com   0   0   9

Now, when I click on
tracker_hadoop..domain.example.com:/127.0.0.1:4545 link it takes me to
http://hadoop.domain.example.com:50060/. But there is no DNS entry for
hadoop in our DNS server. So, I get error in browser. hadoop is just
the locally set name in the master node. From my machine I can't
access the master node as hadoop. I have to access it as IP address
192.168.101.8. So, this link fails. Is there a way I can set it so
that, it doesn't use names but only IP address in forming this link?

Difference between put and copyFromLocal?

[Ben Kucinich]

In bin/hadoop dfs command I find these two options which seems similar to me.

   [-put localsrc dst]
   [-copyFromLocal localsrc dst]

Is there any difference between -put command and -copyFromLocal command?

Similarly what is the difference between -get command and -copyToLocal?