Question Command Line - change start up disk

[rolkenfarn]

I need to change the start up disk to be a different disk instead of my OS X disk.

OS X cannot see the disk I want it to use.

I cannot change the start up disk back in OS X's settings.

How do I use the command line in OS X to fix it?

2009 Macbook Pro
OS X El Capitan

 

[jsmithepa]

Try THIS?

 

[rolkenfarn]

No dice.

I was able to get the files I wanted using an Ubuntu LiveUSB.

Now I really want to get the Firefox History and Extensions.