Ssh connection takes forever to initiate, stuck at “pledge: network”

ssh

Connection to one of my servers using ssh takes more than 20 seconds to initiate.

This is not related to LAN or WAN conditions, since connection to itself takes the same (ssh localhost). After connection is finally establised, it is super fast to interract with the server.

Using -vvv shows that the connection is stuck after saying "pledge: network". At this point, authentication (here using key) is already done, as visible here :

...
debug1: Authentication succeeded (publickey).
Authenticated to myserver.mydomain.com ([xx.xx.xx.xx]:22).
debug1: channel 0: new [client-session]
debug2: channel 0: send open
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network

(…stuck here for 15 to 25 seconds…)

debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug2: callback start
debug2: fd 3 setting TCP_NODELAY
debug2: client_session2_setup: id 0
...

Server is Ubuntu 16.04. It already happened to me in the past with another server (was Ubuntu 12.04) , nerver found the solution and the problem disapeared after a while…

sshd_config is the default one provided by Ubuntu.

So far I have tried :

  • using -o GSSAPIAuthentication=no in the ssh command
  • using password instead of a key
  • using UsePrivilegeSeparation no instead of yes, in sshd_config

Best Answer

This is probably an issue with D-Bus and systemd. If the dbus service is restarted for some reason, you will also need to restart systemd-logind.

You can check if this is the issue by opening the ssh daemon log (on Ubuntu it should be /var/log/auth.log) and check if it has these lines:

sshd[2721]: pam_systemd(sshd:session): Failed to create session: Connection timed out

If yes, just restart systemd-logind service:

systemctl restart systemd-logind

I had this same issue on CentOS 7, because the messagebus was restarted (which is how the D-Bus service is called on CentOS).

Related Topic