I recently got a new raspberry pi (yes, I might have a problem) and wanted to be able to ssh into it without having to remember the IP or password. Luckily I wrote this helpful post several months ago.
While it go me most of the way there, I did run into a slight issue.
First Issue
The issue was that I had a typo for the command to generate a key. I had:
ssh-keyken -t rsa
Which should have been:
ssh-keygen -t rsa
When I copied and pasted the original command the terminal said there was no such command. 🤦‍♂️
Second Issue
Once that go cleared up I went through the steps and was able to get everything set up. Or so I thought. On attempting to ssh into my new pi I was greeted with a password prompt. WTF?
The first thing I did was to check to see what keys were in my ~/.ssh folder. Sure enough there were a couple of them in there.
ls ~/.ssh
id_rsa id_rsa.github id_rsa.github.pub id_rsa.pub known_hosts read_only_key read_only_key.pub
Next, I interrogated the help command for ssh-copy-id to see what flags were available.
Usage: /usr/bin/ssh-copy-id [-h|-?|-f|-n] [-i [identity_file]] [-p port] [[-o <ssh -o options>] ...] [user@]hostname
-f: force mode -- copy keys without trying to check if they are already installed
-n: dry run -- no keys are actually copied
-h|-?: print this help
I figured let’s try the -n flag and get the output from that. Doing so gave me
ryan@Ryans-MBP:~/Desktop$ ssh-copy-id -n pi@newpi
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/Users/ryan/.ssh/id_rsa.github.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: WARNING: All keys were skipped because they already exist on the remote system.
(if you think this is a mistake, you may want to use -f option)
OK … why is it sending the GitHub key? That’s a different problem for a different time. I see another flag available is the -i which will allow me to specify which key I want to send. Aha!
OK, now all that I need to do is use the following command to test the output:
ssh-copy-id -n -i ~/.ssh/id_rsa.pub pi@newpi
And sure enough it’s sending the correct key
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/Users/ryan/.ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: WARNING: All keys were skipped because they already exist on the remote system.
(if you think this is a mistake, you may want to use -f option)
Remove the -n flag to send it for real
ssh-copy-id -i ~/.ssh/id_rsa.pub pi@newpi
And try to ssh in again
ssh pi@newpi
Success!
I wanted to write this up for 2 reasons:
- So I can refer back to it if I ever need to. This blog is mostly for me to write down technical things that I do so I can remember them later on
- This is the first time I’ve run into an issue with a command like tool and simply used the help to figure out how to fix the problem and I wanted to memorialize that. It felt forking awesome to do that.
Footnote: Yes … calling my new raspberry pi newpi in my hosts file is dumb. Yes, when I get my next new Raspberry Pi I will be wondering what to call it. YEs, I am going to try and remember to make the change before it happens so that I don’t end up with the next Pi being called newnewpi and the one after that being newnewnewpi