启动Hadoop时报了一个警告信息，我安装的Hadoop版本是hadoop1.0.4，具体警告信息如下：
[root@localhost hadoop-1.0.4]# ./bin/start-all.sh Warning: $HADOOP_HOME is deprecated.
网上的说法是因为Hadoop本身对HADOOP_HOME做了判断，具体在bin/hadoop和bin/hadoop-config.sh里。在hadoop-config.sh里有如下的配置：
if [ "$HADOOP_HOME_WARN_SUPPRESS" = "" ] && [ "$HADOOP_HOME" != "" ]; then echo "Warning: \$HADOOP_HOME is deprecated." 1>&2 echo 1>&2 fi
对于这个警告问题，解决方法如下：
1.注释掉hadoop-config.sh里的上面给出的这段if fi配置（不推荐）
2.在当前用户home/.bash_profile里增加一个环境变量：
export HADOOP_HOME_WARN_SUPPRESS=1
注：修改完.bash_profile后需要执行source操作使其生效
[root@localhost ~]# source .bash_profile
执行完后我们可以检验一下配置是否成功，重新执行start-all.sh脚本：
[root@localhost hadoop-1.0.4]# ./bin/start-all.sh starting namenode, logging to /root/hadoop-1.0.4/libexec/../logs/hadoop-root-namenode-localhost.out localhost: starting datanode, logging to /root/hadoop-1.0.4/libexec/../logs/hadoop-root-datanode-localhost.out localhost: starting secondarynamenode, logging to /root/hadoop-1.0.4/libexec/../logs/hadoop-root-secondarynamenode-localhost.out starting jobtracker, logging to /root/hadoop-1.0.4/libexec/../logs/hadoop-root-jobtracker-localhost.out localhost: starting tasktracker, logging to /root/hadoop-1.0.4/libexec/../logs/hadoop-root-tasktracker-localhost.out
没有出现Warning: $HADOOP_HOME is deprecated，说明问题已经解决。