I have my own ssh server (on raspberry pi 5, Ubuntu Server 23) but when I try to connect from my PC using key authentication (having password disabled), I get a blank screen. A blinking cursor.
However, once I enter the command eval "$(ssh-agent -s)" and try ssh again, I successfully login after entering my passphrase. I don’t want to issue this command every time. Is that possible?
This does not occur when I have password enabled on the ssh server. Also, ideally, I want to enter my passphrase EVERYTIME I connect to my server, so ideally I don’t want it to be stored in cache or something. I want the passphrase to be a lil’ password so that other people can’t accidentally connect to my server when they use my PC.
As mentioned,
-v(or-vv) helps to analyze the situation.My theory is that you already have something providing ssh agent service, but that process is somehow stuck, and when ssh tries to connect it, it doesn’t respond to the connect, or it accepts the connection but doesn’t actually interact with ssh. Quite possibly ssh doesn’t have a timeout for interacting with ssh-agent.
Using
eval $(ssh-agent -s)starts a new ssh agent and replaces the environment variables in question with the new ones, therefore avoiding the use of the stuck process.If this is the actual problem here, then before running the
eval,echo $SSH_AUTH_SOCKwould show the path of the existing ssh agent socket. If this is the case, then you can uselsof $SSH_AUTH_SOCKto see what that process is. Quite possibly it’s provided bygnome-keyring-daemonif you’re running Gnome. As to why that process would not be working I don’t have ideas.Another way to analyze the problem is
strace -o logfile -f ssh ..and then check out what is at the end of thelogfile. If the theory applies, then it would likely be aconnectcall for the ssh-agent.which sshwhich ssh-agentI guess it’s worth checking if those names point to the expected binaries, but I also think it would be highly unlikely they would be anything else than just
/usr/bin/sshand/usr/bin/ssh-agent.