Ubuntu一直在登陆界面循环：登陆密码是正确的，但是登陆后自动退回登陆界面。
这个问题原因应该很多，上网看了些可能有些启发，但是最终还是得看自己的问题。
我以为我要抛弃这个系统重新安装了，那是很杯具了，还好最终发现并解决了问题。
我发现，一方面我通过SSH可以登录进去系统，会报一些错误：
Last login: Tue Jun 26 02:32:21 2018 from 192.168.23.1
-bash: /opt/apache-hive-2.1.1-bin/bin: Is a directory
Command ‘lesspipe’ is available in the following places
* /bin/lesspipe
* /usr/bin/lesspipe
The command could not be located because ‘/bin:/usr/bin’ is not included in the PATH environment variable.
lesspipe: command not found
Command ‘dircolors’ is available in ‘/usr/bin/dircolors’
The command could not be located because ‘/usr/bin’ is not included in the PATH environment variable.
dircolors: command not found
Command ‘ls’ is available in ‘/bin/ls’
The command could not be located because ‘/bin’ is not included in the PATH environment variable.
ls: command not found
在登录的图形界面用Ctrl+Alt+F1~F6进入命令行界面同样报类似信息。
而且两种方式下，很多命令都执行不了。
还好可以执行export:
xx@ubuntu:~$ export PATH=$PATH:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/local/hadoop/bin:/usr/local/hadoop/sbin
执行完后就可以执行很多命令了。
联想到之前安装HIVE，修改了profile文件，赶紧进去看看：
xx@ubuntu:/$ sudo vi etc/profile
export HIVE_HOME=/opt/apache-hive-2.1.1-bin
export PATH=$HIVE_HOME/bin;$PATH
果然，设置PATH时用了;号导致PATH路径错误，系统起不来了。
修改文件中;为:号后，重启系统就可以正常登录了