I'm using Ubuntu 16.04 and OpenSSH in my VPS. Everytime I log in via ssh, eventually connection is lost. I can't type anything. I need to close terminal and open it again. But, after try to login again, I always get a message ssh: connect to host xxx.xxx.xxx.xxx port 39904: Resource temporarily unavailable. And after that I need to wait at least 2 minutes before be able to login again.
I really don't know what is going on. When I saw /var/log/auth.log, there was a lot of entries similar to:
May 1 19:41:21 vps20999 sshd[40006]: Received signal 15; terminating. May 1 19:41:21 vps20999 sshd[40571]: Server listening on 0.0.0.0 port 39904. Pointing to exact time when I lose connection with SSH. It is a clean machine. It only has, for now, OpenSSH and UFW. Does someone know what is happening?
I'm using the following SSH configurations:
# /etc/ssh/sshd_config # SSH Configuration # Connection Port Port 39904 # Protocol Connection Protocol 2 # HostKeys for protocol version 2 HostKey /etc/ssh/ssh_host_rsa_key HostKey /etc/ssh/ssh_host_dsa_key HostKey /etc/ssh/ssh_host_ecdsa_key HostKey /etc/ssh/ssh_host_ed25519_key #Privilege Separation is turned on for security UsePrivilegeSeparation yes # Lifetime and size of ephemeral version 1 server key KeyRegenerationInterval 3600 ServerKeyBits 1024 # Logging SyslogFacility AUTH LogLevel INFO # Authentication LoginGraceTime 120 PermitRootLogin no StrictModes yes RSAAuthentication yes PubkeyAuthentication yes AuthorizedKeysFile %h/.ssh/authorized_keys # Don't read the user's ~/.rhosts and ~/.shosts files IgnoreRhosts yes # For this to work you will also need host keys in /etc/ssh_known_hosts RhostsRSAAuthentication no # similar for protocol version 2 HostbasedAuthentication no # To enable empty passwords, change to yes (NOT RECOMMENDED) PermitEmptyPasswords no # Change to yes to enable challenge-response passwords (beware issues with # some PAM modules and threads) ChallengeResponseAuthentication no # Change to no to disable tunnelled clear text passwords PasswordAuthentication no X11Forwarding yes X11DisplayOffset 10 PrintMotd no PrintLastLog yes TCPKeepAlive yes MaxStartups 3:50:6 Banner /etc/issue.net # Allow client to pass locale environment variables AcceptEnv LANG LC_* Subsystem sftp /usr/lib/openssh/sftp-server # Set this to 'yes' to enable PAM authentication, account processing, # and session processing. If this is enabled, PAM authentication will # be allowed through the ChallengeResponseAuthentication and # PasswordAuthentication. Depending on your PAM configuration, # PAM authentication via ChallengeResponseAuthentication may bypass # the setting of "PermitRootLogin yes # If you just want the PAM account and session checks to run without # PAM authentication, then enable this but set PasswordAuthentication # and ChallengeResponseAuthentication to 'no'. UsePAM yes # Access only IPv4 AddressFamily inet # Groups and Users AllowGroups sshdroplet sftponly DenyUsers root DenyGroups root ClientAliveInterval 120 ClientAliveCountMax 150 
