It worked last night, and I haven't rebooted the server since then (it was copying a few hundred GB from one USB hard drive to another, otherwise doing nothing), but now I can only do this:
aaron@aaron-VirtualDesktop:~$ ping 192.168.0.100
PING 192.168.0.100 (192.168.0.100) 56(84) bytes of data.
64 bytes from 192.168.0.100: icmp_seq=1 ttl=63 time=1.57 ms
64 bytes from 192.168.0.100: icmp_seq=2 ttl=63 time=2.60 ms
64 bytes from 192.168.0.100: icmp_seq=3 ttl=63 time=2.14 ms
64 bytes from 192.168.0.100: icmp_seq=4 ttl=63 time=2.56 ms
64 bytes from 192.168.0.100: icmp_seq=5 ttl=63 time=7.41 ms
^C
--- 192.168.0.100 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4007ms
rtt min/avg/max/mdev = 1.575/3.258/7.412/2.109 ms
aaron@aaron-VirtualDesktop:~$ ssh [email protected] -vvv
OpenSSH_7.2p2 Ubuntu-4ubuntu2.2, OpenSSL 1.0.2g 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "192.168.0.100" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.0.100 [192.168.0.100] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/aaron/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/aaron/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/aaron/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/aaron/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/aaron/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/aaron/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/aaron/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/aaron/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
ssh_exchange_identification: read: Connection reset by peer
aaron@aaron-VirtualDesktop:~$
The only existing question I could find with the same error messages is this, which was dropped without much discussion and with no answers: https://serverfault.com/q/799207
I really don't want to just pull the plug and reboot, so is there a way to fix this using the current session?
.sshdirectory does indeed exist./home/aaron/.ssh/wasknown_hosts, which had the key in it.