No logs were left on the client. However, strange parts of the sshd debug log have been identified.
--------------------------------------- /var/log/auth.log ------------------- Jul 10 19:55:37 debian systemd-logind[481]: Watching system buttons on /dev/input/event4 (Power Button) Jul 10 19:55:37 debian sshd[468]: Server listening on 0.0.0.0 port 22. Jul 10 19:55:37 debian sshd[468]: Server listening on :: port 22. Jul 10 19:55:37 debian sshd[468]: Received SIGHUP; restarting. Jul 10 19:55:37 debian sshd[468]: Server listening on 0.0.0.0 port 22. Jul 10 19:55:37 debian sshd[468]: Server listening on :: port 22. Jul 10 19:55:39 debian sshd[755]: Accepted password for koov from 192.168.0.2 port 2741 ssh2 Jul 10 19:55:40 debian sshd[755]: pam_unix(sshd:session): session opened for user koov by (uid=0) Jul 10 19:55:40 debian systemd-logind[481]: New session 1 of user koov. Jul 10 19:55:40 debian systemd: pam_unix(systemd-user:session): session opened for user koov by (uid=0) Jul 10 19:57:33 debian sshd[471]: Server listening on 0.0.0.0 port 22. Jul 10 19:57:33 debian sshd[471]: Server listening on :: port 22. Jul 10 19:57:33 debian systemd-logind[483]: New seat seat0. Jul 10 19:57:33 debian systemd-logind[483]: Watching system buttons on /dev/input/event4 (Power Button) Jul 10 19:57:34 debian sshd[471]: Received SIGHUP; restarting. Jul 10 19:57:34 debian sshd[471]: Server listening on 0.0.0.0 port 22. Jul 10 19:57:34 debian sshd[471]: Server listening on :: port 22. Jul 10 19:58:04 debian login[484]: pam_unix(login:session): session opened for user root by LOGIN(uid=0) Jul 10 19:58:04 debian systemd-logind[483]: New session 1 of user root. Jul 10 19:58:04 debian systemd: pam_unix(systemd-user:session): session opened for user root by (uid=0) Jul 10 19:58:04 debian login[760]: ROOT LOGIN on '/dev/tty1' Jul 10 19:59:14 debian sshd[471]: Received signal 15; terminating. Jul 10 19:59:14 debian sshd[781]: debug1: Set /proc/self/oom_score_adj from 0 to -1000 Jul 10 19:59:14 debian sshd[781]: debug1: Bind to port 22 on 0.0.0.0. Jul 10 19:59:14 debian sshd[781]: Server listening on 0.0.0.0 port 22. Jul 10 19:59:14 debian sshd[781]: debug1: Bind to port 22 on ::. Jul 10 19:59:14 debian sshd[781]: Server listening on :: port 22. Jul 10 19:59:29 debian sshd[781]: debug1: Forked child 788. Jul 10 19:59:29 debian sshd[788]: debug1: Set /proc/self/oom_score_adj to 0 Jul 10 19:59:29 debian sshd[788]: debug1: rexec start in 5 out 5 newsock 5 pipe 7 sock 8 Jul 10 19:59:29 debian sshd[788]: debug1: inetd sockets after dupping: 3, 3 Jul 10 19:59:29 debian sshd[788]: Connection from 192.168.0.2 port 2786 on 192.168.0.226 port 22 Jul 10 19:59:29 debian sshd[788]: debug1: Client protocol version 2.0; client software version nsssh2_5.0.0039 NetSarang Computer, Inc. Jul 10 19:59:29 debian sshd[788]: debug1: no match: nsssh2_5.0.0039 NetSarang Computer, Inc. Jul 10 19:59:29 debian sshd[788]: debug1: Local version string SSH-2.0-OpenSSH_7.4p1 Debian-10 Jul 10 19:59:29 debian sshd[788]: debug1: Enabling compatibility mode for protocol 2.0 Jul 10 19:59:29 debian sshd[788]: debug1: permanently_set_uid: 107/65534 [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: list_hostkey_types: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519 [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: SSH2_MSG_KEXINIT sent [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: SSH2_MSG_KEXINIT received [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: kex: algorithm: [email protected] [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: kex: host key algorithm: ssh-rsa [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: expecting SSH2_MSG_KEX_ECDH_INIT [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: rekey after 4294967296 blocks [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: SSH2_MSG_NEWKEYS sent [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: expecting SSH2_MSG_NEWKEYS [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: SSH2_MSG_NEWKEYS received [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: rekey after 4294967296 blocks [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: KEX done [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: userauth-request for user koov service ssh-connection method none [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: attempt 0 failures 0 [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: PAM: initializing for "koov" Jul 10 19:59:29 debian sshd[788]: debug1: PAM: setting PAM_RHOST to "192.168.0.2" Jul 10 19:59:29 debian sshd[788]: debug1: PAM: setting PAM_TTY to "ssh" Jul 10 19:59:29 debian sshd[788]: debug1: userauth-request for user koov service ssh-connection method password [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: attempt 1 failures 0 [preauth] Jul 10 19:59:29 debian sshd[788]: debug1: PAM: password authentication accepted for koov Jul 10 19:59:29 debian sshd[788]: debug1: do_pam_account: called Jul 10 19:59:29 debian sshd[788]: Accepted password for koov from 192.168.0.2 port 2786 ssh2 Jul 10 19:59:29 debian sshd[788]: debug1: monitor_child_preauth: koov has been authenticated by privileged process Jul 10 19:59:29 debian sshd[788]: debug1: monitor_read_log: child log fd closed Jul 10 19:59:29 debian sshd[788]: debug1: PAM: establishing credentials Jul 10 19:59:29 debian sshd[788]: pam_unix(sshd:session): session opened for user koov by (uid=0) Jul 10 19:59:29 debian systemd-logind[483]: New session 3 of user koov. Jul 10 19:59:29 debian systemd: pam_unix(systemd-user:session): session opened for user koov by (uid=0) Jul 10 19:59:29 debian sshd[788]: User child is on pid 797 Jul 10 19:59:29 debian sshd[797]: debug1: SELinux support disabled Jul 10 19:59:29 debian sshd[797]: debug1: PAM: establishing credentials Jul 10 19:59:29 debian sshd[797]: debug1: permanently_set_uid: 1000/1000 Jul 10 19:59:29 debian sshd[797]: debug1: rekey after 4294967296 blocks Jul 10 19:59:29 debian sshd[797]: debug1: rekey after 4294967296 blocks Jul 10 19:59:29 debian sshd[797]: debug1: ssh_packet_set_postauth: called Jul 10 19:59:29 debian sshd[797]: debug1: Entering interactive session for SSH2. Jul 10 19:59:29 debian sshd[797]: debug1: server_init_dispatch Jul 10 19:59:29 debian sshd[797]: debug1: server_input_channel_open: ctype session rchan 0 win 32768 max 16384 Jul 10 19:59:29 debian sshd[797]: debug1: input_session_request Jul 10 19:59:29 debian sshd[797]: debug1: channel 0: new [server-session] Jul 10 19:59:29 debian sshd[797]: debug1: session_new: session 0 Jul 10 19:59:29 debian sshd[797]: debug1: session_open: channel 0 Jul 10 19:59:29 debian sshd[797]: debug1: session_open: session 0: link with channel 0 Jul 10 19:59:29 debian sshd[797]: debug1: server_input_channel_open: confirm session Jul 10 19:59:29 debian sshd[797]: debug1: server_input_channel_req: channel 0 request x11-req reply 1 Jul 10 19:59:29 debian sshd[797]: debug1: session_by_channel: session 0 channel 0 Jul 10 19:59:29 debian sshd[797]: debug1: session_input_channel_req: session 0 req x11-req Jul 10 19:59:29 debian sshd[797]: debug1: channel 1: new [X11 inet listener] Jul 10 19:59:29 debian sshd[797]: debug1: channel 2: new [X11 inet listener] Jul 10 19:59:29 debian sshd[797]: debug1: server_input_channel_req: channel 0 request pty-req reply 0 Jul 10 19:59:29 debian sshd[797]: debug1: session_by_channel: session 0 channel 0 Jul 10 19:59:29 debian sshd[797]: debug1: session_input_channel_req: session 0 req pty-req Jul 10 19:59:29 debian sshd[797]: debug1: Allocating pty. Jul 10 19:59:29 debian sshd[788]: debug1: session_new: session 0 Jul 10 19:59:29 debian sshd[788]: debug1: SELinux support disabled Jul 10 19:59:29 debian sshd[797]: debug1: session_pty_req: session 0 alloc /dev/pts/0 Jul 10 19:59:29 debian sshd[797]: debug1: server_input_channel_req: channel 0 request shell reply 0 Jul 10 19:59:29 debian sshd[797]: debug1: session_by_channel: session 0 channel 0 Jul 10 19:59:29 debian sshd[797]: debug1: session_input_channel_req: session 0 req shell Jul 10 19:59:29 debian sshd[797]: Starting session: shell on pts/0 for koov from 192.168.0.2 port 2786 id 0 Jul 10 19:59:29 debian sshd[799]: debug1: Setting controlling tty using TIOCSCTTY. ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@Jul 10 20:00:20 debian systemd-logind[505]: New seat seat0. Jul 10 20:00:20 debian systemd-logind[505]: Watching system buttons on /dev/input/event4 (Power Button) Jul 10 20:00:21 debian sshd[486]: debug1: Set /proc/self/oom_score_adj from 0 to -1000 Jul 10 20:00:21 debian sshd[486]: debug1: Bind to port 22 on 0.0.0.0. Jul 10 20:00:21 debian sshd[486]: Server listening on 0.0.0.0 port 22. Jul 10 20:00:21 debian sshd[486]: debug1: Bind to port 22 on ::. Jul 10 20:00:21 debian sshd[486]: Server listening on :: port 22. Jul 10 20:00:21 debian sshd[486]: Received SIGHUP; restarting. Jul 10 20:00:21 debian sshd[486]: debug1: Set /proc/self/oom_score_adj to 0 Jul 10 20:00:21 debian sshd[486]: debug1: Set /proc/self/oom_score_adj from 0 to -1000 Jul 10 20:00:21 debian sshd[486]: debug1: Bind to port 22 on 0.0.0.0. Jul 10 20:00:21 debian sshd[486]: Server listening on 0.0.0.0 port 22. Jul 10 20:00:21 debian sshd[486]: debug1: Bind to port 22 on ::. Jul 10 20:00:21 debian sshd[486]: Server listening on :: port 22. Jul 10 20:00:29 debian login[507]: pam_unix(login:session): session opened for user root by LOGIN(uid=0) Jul 10 20:00:29 debian systemd-logind[505]: New session 1 of user root. Jul 10 20:00:29 debian systemd: pam_unix(systemd-user:session): session opened for user root by (uid=0) Jul 10 20:00:30 debian login[782]: ROOT LOGIN on '/dev/tty1' Jul 10 20:03:58 debian sshd[484]: debug1: Set /proc/self/oom_score_adj from 0 to -1000 Jul 10 20:03:58 debian sshd[484]: debug1: Bind to port 22 on 0.0.0.0. Jul 10 20:03:58 debian sshd[484]: Server listening on 0.0.0.0 port 22. Jul 10 20:03:58 debian sshd[484]: debug1: Bind to port 22 on ::. Jul 10 20:03:58 debian sshd[484]: Server listening on :: port 22. Jul 10 20:03:59 debian systemd-logind[486]: New seat seat0. Jul 10 20:03:59 debian systemd-logind[486]: Watching system buttons on /dev/input/event4 (Power Button) Jul 10 20:03:59 debian sshd[484]: Received SIGHUP; restarting. Jul 10 20:03:59 debian sshd[484]: debug1: Set /proc/self/oom_score_adj to 0 Jul 10 20:03:59 debian sshd[484]: debug1: Set /proc/self/oom_score_adj from 0 to -1000 Jul 10 20:03:59 debian sshd[484]: debug1: Bind to port 22 on 0.0.0.0. Jul 10 20:03:59 debian sshd[484]: Server listening on 0.0.0.0 port 22. ------------------------------------- end of /var/log/auth.log --------------------------------------- Jul 10 19:59:29 This is where the system hangs while trying to log in. Strangely, the ^@ mark was printed too much. And I force rebooted Jul 10 20:00:20 I hope it helps. 2017-07-10 17:42 GMT+09:00 Colin Watson <[email protected]>: > On Mon, Jul 10, 2017 at 01:54:25PM +0900, 이강우 wrote: > > PS: There is nothing in the log file. > > The server will be stopped(hang. power is on) momentarily and no messages > > will be left in the log. > > How about the client log? Can you crank up the client's debugging as > high as possible and at least see how far it gets in the SSH exchange? > > A system hang like this can only be a kernel bug, I think. > > -- > Colin Watson [[email protected]] >
