hadoop格式出现如下问题，该怎么解决？
[root@localhost jvm]# cd /opt/hadoop-1.2.1/bin/
[root@localhost bin]# hadoop namenode -format
/opt/hadoop-1.2.1/bin/hadoop: line 350: /usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/bin/java: No such file or directory
/opt/hadoop-1.2.1/bin/hadoop: line 434: /usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/bin/java: No such file or directory
/opt/hadoop-1.2.1/bin/hadoop: line 434: exec: /usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/bin/java: cannot execute: No such file or directory
