Error in host address encountered while executing Spark-shell

Spark 1.4 was downloaded and the following error was encountered while executing Spark-shell:

Java.net.unknownhostexception:ukon-m-q0ep:ukon-m-q0ep:nodename nor servname provided, or not known
At Java.net.InetAddress.getLocalHost (inetaddress.java:1473)

This is not a spark-specific error, but a common problem with using Java on Mac, which is that application cannot query the IP address when querying the host's corresponding IP address.

UKON-M-Q0EPThis is the hostname of my Mac, which can be queried via Mac Terminal hostname command:

Ukon-m-q0ep:~ ukon$ hostname
Ukon-m-q0ep

However, the system cannot find the IP address of this hostname (in fact I am not quite able to understand why I cannot find it.) Wouldn't the system be a little smarter? But it does not, this can be verified by the following command:

ukon-m-q0ep:~ ukon$ Ping Ukon-m-q0ep
^c

But suppose I /etc/hosts add this hostname to the file and 127.0.0.1 ping it on the line:

ukon-m-q0ep:~ ukon$ Ping Ukon-m-q0ep
PING Ukon-m-q0ep (127.0.0.1): Data bytes
Bytes from 127.0.0.1:icmp_seq=0 ttl=64 time=0.056 ms
Bytes from 127.0.0.1:icmp_seq=1 ttl=64 time=0.133 ms
Bytes from 127.0.0.1:icmp_seq=2 ttl=64 time=0.121 ms
Bytes from 127.0.0.1:icmp_seq=3 ttl=64 time=0.134 ms
^c

As can be seen, the system does require us to manually configure the/etc/hosts in order to find the host's IP address.

Run ./bin/spark-shell it again, it's done.

ukon-m-q0ep:spark-1.4.0-bin-hadoop2.6 ukon$./bin/spark-shell
2015-07-04 00:12:04.604 java[31755:1803488] Unable to load realms info from Scdynamicstore
Welcome to
__
/ / _ _/ /__
\ \ \/_ '/ _/'/
// . /_,////_\ version 1.4.0
/_/

Using Scala version 2.10.4 (Java HotSpot (TM) 64-bit Server VM, Java 1.7.0_45)
Type in expressions to has them evaluated.
Type:help for more information.
Spark context available as SC.
SQL context available as SqlContext.

Scala>

done!

And then. Successfully executed a spark code that counts the number of rows in a local file and queries the text content of the first line:

scala> val textfile = Sc.textfile ("readme.md")
Textfile:org.apache.spark.rdd.rdd[string] = mappartitionsrdd[1] at textfile at:21

Scala> Textfile.count ()
Res0:long = 98

Scala> Textfile.first ()
res1:string = # Apache Spark

Very cool!

Error in host address encountered while executing Spark-shell