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Killing ssh-agent deletes socketfile on one debian, on another debian it remains
(stackoverflow.com)
this post was submitted on 04 Aug 2023
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I don't really have an answer but why would you even want two running agents using the same socket file path, one with an unlinked socket and one with a socket actually existing in the filesystem? I assume you want to avoid a gap between stopping the old and starting the new agent?
My next step would probably be to check the openssh source code for the bit that removes the socket file to see what kind of conditions there are and maybe also try strace or similar tools to see if it does not remove it because the removal fails or because it is never attempted.
I start for every connection-group an own ssh-agent with different ssh-keys in it. And i connect from my laptop sometimes (regulary) to my desktop-machine and forward the agent to the desktop. This is a setup, i need.
And i have a script, which chooses from ssh config, (Match section) the ssh-agent i need for this connection-group. This script starts automatically an ssh-agent and loads the identities (private-keys, hardware-token...) into this ssh-agent and per configfile it is choosen as IdentityAgent.
When i'm connected to my desktop with my laptop and i work on my desktop, then i use the forwarded agent, because i have some keys only on my laptop, which i want to use also from my desktop. So i link the forwarded agent-socket to the IdentityAgent, which is configured in ssh-config for this connection... When there is no forwared ssh-agent, the symlink is deleted and a new agent is started with a socketfile on the same path.
It sound's a bit complicated... and yes, it is.
An i don't get it, why sometimes the socketfile is deleted and sometimes it remains. Now i tested it from home on the remote-connection. The temporary, forwarded agent-socket is a symlink to my regular socket-file. and i killed the running ssh-agent... and also the symlink is removed.
It is strange behaviour... a process unlinks a socket-file, which does not belong to him, only the name is the same... and not every time.
That is what I would expect it to do actually. I would expect it to close the socket it has open and the delete (unlink) it by name.
I expect, it deletes the socket, which on which the process is listening. what if i rename the socket (for some reason). Then the socketfile should be deleted also.
Directory operations like unlinking (deletion) traditionally work via paths, not open file handles.