SSH first logon too slow problem

These two days in the use of Docker test, found that the new container in the first SSH login time often timed out, we simply set the timeout time to 60 seconds, but still occasionally timed out. So the simple delay timeout blocked.

So I thought about whether I could fix the problem by modifying the parameters of sshd. Probably checked. SSH logon too slow may be a problem with DNS resolution, the default configuration ssh initial accept SSH connection will automatically reverse resolution client IP address to get SSH client host name. If there is a problem with the reverse resolution of DNS at this point, sshd will wait until the DNS resolution times out before providing an SSH connection.

The solution is to modify the/etc/ssh/sshd_config file, which

#UseDNS Yes

To

Usedns No

Then restart the sshd service.