Incorrect hostname in terminal after factory reset
1.) red-panda is your current computer name.


Click Apple Menu on Top Left
Open the System Preferences... App
Type Computer Name in Search
Change the red-panda to whatever you like, I would suggest something short, like KM, if you plan to use Terminal a lot
Close System Preferences... App




To securely wipe your hard drive, do an after-restart system reinstall and pick the proper option.

For more info and useful tips on how not to lose your own data before doing it, read some articles like this: 


What to do before you sell, give away, or trade in your Mac 
How to reset your Mac before selling it




2. No, no trouble for no hostname. The hostname is not set by default upon install.

However, if you wish to set it, execute: scutil --set HostName desired-hostname-here-again-I-suggest-a-short-name-like-kmp in Terminal.