Glad you were able to get things working!
For future reference, on most OS's, root is the default user you'll need to use to login initially. CoreOS is one exception.
If you run in to any other issues, feel free to reply and I'll be more than happy to help!
You know how I got this to work after not finding any workable solution?? Logged into console, edited ~/.ssh/authorized_keys using NANO and manually typed out the new ssh key...
Was locked out due to disabling password authentication and Permission denied (publickey).
On a Mac, wrote an AppleScript to type.
In Script Editor located /Applications/Utilities/Script Editor
tell application "System Events"
set textToType to "ssh-rsa AAAAB..."
delay 20
repeat with i from 1 to count characters of textToType
keystroke (character i of textToType)
delay 0.6
end repeat
end tell
Make sure to have ~/.ssh/authorized_keys already open in an editor and in insert mode waiting to type
Press play
After a 20 second delay (hopefully, enough time to change to the console browser window ready for the typing to start) this will type the text inside set textToType to emulating keystrokes
That's the point. I can't do any of that stuff because I can't get ssh to work, and I can't try to get the keys to work manually because I can't copy or paste.
I've had to manually type in my local machines public ssh key from the DigitalOcean web console as well and it sucks. There's no other way as far as I'm aware if you've disabled password authentication on your server.
Here's a python script you can use client-side to type for you...
#!/usr/bin/env python3
import subprocess
import time
import sys
text = "ssh-rsa tvHiU_VERY_LONG_KEY_sadf== you@gmail.com"
# 3 seconds to alt-tab to correct window after running
time.sleep(3)
for ch in text:
# type out the text
subprocess.call(["xdotool", "type", ch])
# increase or decrease the time below to type slower or faster
time.sleep(0.15)