https://www.youtube.com/watch?v=h5PRvBpLuJs
3 main methods:
(1)use UART adapter to talk to debug parts, get to the device where we shouldn‘t be able to.
“UART是一种通用串行数据总线，用于异步通信。该总线双向通信，可以实现全双工传输和接收。在嵌入式设计中，UART用来与PC进行通信，包括与监控调试器和其它器件，如EEPROM通信。”
“在手机设计和测试阶段被用来控制CPU与其余部分的訊息传送”
视频中利用UART直接和硬件device通信（感觉像是用UART来触发了debug的功能，后面便可以用debug的命令行来进行后续操作），来获取硬件的控制权，或者进行其他想要的操作。
如连接UART的情况下启动printer, printer会显示这样的console menu:
可以在console上选择自己想要的功能 （居然还可以enter shell command..这样就可以自由发挥啦）
还可以用UART来更改U Boot的设置，比如修改登陆密码等，修改完之后再登录。
(2) use EMMC, SD-card like. connect to EMMC to modify storage.
(3)
（未完待续！！待续！）
来几个youtube上的评论好啦：
‘It gives some the ability to make software that would otherwise be incapable of running due to limitations of the OS or UI. It gives you complete access to the devices direct underlying OS (typically, if not always, linux). In the case of an end user it would give you the ability to run software written under this guise. For most users, this is meaningless. For some the point is that they make a device using technology and then lock out that technology (ie: my cell phone supports ALL cell technologies, but they locked out the 4G LTE method, it‘s still there in teh hardware but hidden in the software, by rooting it and installing a patch I can now use 4G LTE). Essentially, gives you control over your device that you only had limited control before. It‘s not for everybody.’
‘I‘d think twice about putting a bunch of IoT stuff in my home. Especially smart locks on the front door. They better have some super robust IT Security built into them if I‘m going to entertain the thought.’