hadoop 启动问题？

我在一台虚拟机上执行 hadoop-damenon.sh start namenode没问题，在另一台虚拟机上以hadoop身份启动datanode时提示starting datanode, logging to /home/hadoop/apps/hadoop-2.6.4/logs/hadoop-hadoop-datanode-mini2.out
/home/hadoop/apps/hadoop-2.6.4/bin/hdfs: line 276: /root/apps/jdk1.7.0_45/bin/java: 权限不够
/home/hadoop/apps/hadoop-2.6.4/bin/hdfs: line 276: exec: /root/apps/jdk1.7.0_45/bin/java: cannot execute: 权限不够，而当切换到root身份时执行此命令，显示starting datanode, logging to /home/hadoop/apps/hadoop-2.6.4/logs/hadoop-hadoop-datanode-mini2.out
/home/hadoop/apps/hadoop-2.6.4/bin/hdfs: line 276: /root/apps/jdk1.7.0_45/bin/java: 没有那个文件或目录
/home/hadoop/apps/hadoop-2.6.4/bin/hdfs: line 276: exec: /root/apps/jdk1.7.0_45/bin/java: cannot execute: 没有那个文件或目录，请大神解决？