# Command

#### chmod
* [Difference between using “chmod a+x” and “chmod 755”](http://stackoverflow.com/questions/18596778/difference-between-using-chmod-ax-and-chmod-755)

#### xxd
* [Viewing File in Binary in Terminal](http://stackoverflow.com/questions/1765311/viewing-file-in-binary-in-terminal)

#### sudo
* [充分发挥 sudo 的作用](http://www.ibm.com/developerworks/cn/aix/library/au-sudo/index.html)

# Command

#### chmod
* [Difference between using “chmod a+x” and “chmod 755”](http://stackoverflow.com/questions/18596778/difference-between-using-chmod-ax-and-chmod-755)

#### xxd
* [Viewing File in Binary in Terminal](http://stackoverflow.com/questions/1765311/viewing-file-in-binary-in-terminal)

#### sudo
* [充分发挥 sudo 的作用](http://www.ibm.com/developerworks/cn/aix/library/au-sudo/index.html)

#### Add and Delete User
* [How To Add and Delete Users on a CentOS 7 Server](https://www.digitalocean.com/community/tutorials/how-to-add-and-delete-users-on-a-centos-7-server)

Add Add and Delete User
Add Add and Delete User
