If you put HDFS in
safe mode at the beginning of this procedure, leave safe mode with
a command that is similar to the following:
$HADOOP_HOME/bin/hdfs dfsadmin -safemode leave
To confirm that the
additional machines are used, you can copy a file to HDFS and then
list the locations of the blocks. Use a command that is similar to
the following:
$HADOOP_HOME/bin/hadoop fs -D dfs.blocksize=512 -put /etc/fstab /hps
Note: The very small block size
shown in the example is used to increase the number of blocks written
and increase the likelihood that the new machines are used.
You can list the block
locations with a command that is similar to the following:
$HADOOP_HOME/bin/hdfs fsck /hps/fstab -files -locations -blocks
Review the output to
check for IP addresses for the new machines.
Connecting to namenode via http://0.0.0.0:50070
FSCK started by hdfs (auth:SIMPLE) from /192.168.9.156 for path /hps/fstab at Wed Jan 30 09:45:24 EST 2013
/hps/fstab 2093 bytes, 5 block(s): OK
0. BP-1250061202-192.168.9.156-1358965928729:blk_-2796832940080983787_1074 len=512 repl=2 [192.168.8.217:50010, 192.168.8.230:50010]
1. BP-1250061202-192.168.9.156-1358965928729:blk_-7759726019690621913_1074 len=512 repl=2 [192.168.8.230:50010, 192.168.8.153:50010]
2. BP-1250061202-192.168.9.156-1358965928729:blk_-6783529658608270535_1074 len=512 repl=2 [192.168.9.159:50010, 192.168.9.158:50010]
3. BP-1250061202-192.168.9.156-1358965928729:blk_1083456124028341178_1074 len=512 repl=2 [192.168.9.158:50010, 192.168.9.160:50010]
4. BP-1250061202-192.168.9.156-1358965928729:blk_-4083651737452524600_1074 len=45 repl=2 [192.168.8.230:50010, 192.168.8.153:50010]
Delete the sample file:
$HADOOP_HOME/bin/hadoop fs -rm /hps/fstab