For a long time, I was baffled by why ssh command was asking for a password sometimes, and sometimes not. Even when I was using the same private/public key pair on many different clusters, I was sometimes getting asked for a password, and sometimes I was not.

Today I tried accessing a cluster that normally requires a password when I try to ssh into it. Normally, to access the cluster I do ssh <ip address>. Today, I did ssh <username>@<ip address> to get in, and it did not ask me for a password!

And, it hasn't asked me for a password since then. This is strange...why does just providing the username cause it to not prompt me for a password anymore? or is there something else that I'm missing that might have changed this?

I checked the permissions on the ~/.ssh directory and everything looks correct there....what other things to check?

closed as unclear what you're asking by Gilles, Stephen Rauch, Kusalananda, GAD3R, Rui F Ribeiro Aug 27 '17 at 15:20

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    Could you share your .ssh/config or relevant portions thereof? If you're using ControlMaster and ControlPersist, then the first connection will establish a control socket that later connections may use without authenticating (see the ssh_config manual). – Kusalananda Aug 26 '17 at 6:30
  • sure, @Kusalananda one second. I can tell you for sure that I do not have ControlMaster and I do not have ControlPersist. So, whatever the default values are for those are what I'm using. I DO however have ForwardingAgent Yes, which might be making a difference here, as was pointed about by some people previously. – guimption Aug 26 '17 at 23:28
  • Please don't use comments to clarify your question and/or respond to requests for more information; instead,  edit your question to make it clearer and more complete. – Scott Aug 27 '17 at 6:12

I suspect you have a password on the ssh private key, and that ssh-agent are running somewhere.

When the first connection is made, and there is nothing in the ssh-agent, then it'll ask you the decryption password for the private key. Once it is entered, it'll add it to the ssh-agent, and that'll then (on subsequent connections until it gets cleared) use the key from the ssh-agent.

  • I do not have enough points to vote right now, but thank you. – guimption Aug 26 '17 at 23:29
  • So @Hvisage you suspect that the client's ssh agent probably did not have this private key attached, and therefore when I first was prompted for the password, it somehow permanently associated my private key with that password, and thus I did not have to enter a password ever since. Is that what you're saying? I could understand that being true if I was only asked for a password once, but that is not the case - I was asked for a password every time I ssh'd for the past week. It was only yesterday that I stopped needing a password. Do you have any clue why that might be happening? Thanks. – guimption Aug 27 '17 at 0:06
  • My only other hypothesis is if the ssh-agent was somehow not running, unbeknownst to me, and at some point it got started yesterday. and, after it got started, every time after that I did not need my ssh password. Do you agree with that? – guimption Aug 27 '17 at 0:06
  • one way to test your hypothesis, would be to disable the ssh-agent on the client side, and then ssh into the server. Then, I could see if it keeps prompting me for a password again and again. Then I could enable the ssh-agent, add the private key to it via ssh-add ~/.ssh/id_rsa and see if it only prompts me for the password once, and then does NOT prompt me any time after that? – guimption Aug 27 '17 at 0:11
  • Sounds about right :) – Hvisage Sep 7 '17 at 22:47

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