다른 인스턴스들은 문제가 없는 상황에서,
[핑계사전] 프로젝트의 프론트엔드 앱을 배포한 서버 인스턴스가 접속 불가능한 현상이 있었음
Connection to 134.185.112.18 closed by remote host.
Connection to 134.185.112.18 closed.
유사한 다른 명령어를 사용하거나, 인스턴스를 재부팅하는 등 어떤 방법을 사용해도 접속할 수 없었고, 구글링해도 정보가 없어 인스턴스 삭제 후 재생성을 고려하던 도중
Claude의 도움을 받아 원인 발견에 성공함
접속하고 서버와 연결이 끊어지기 전 로그를 확인하는 명령어 실행
ssh -i "D:\\oracle_cloud\\exdict-frontend-sshkey\\ssh-key-2026-02-01.key" -t [email protected] "tail -50 /var/log/auth.log"
AzureAD+조한재@DESKTOP-VSL87RR MINGW64 ~
$ ssh -i "D:\\oracle_cloud\\exdict-frontend-sshkey\\ssh-key-2026-02-01.key" -t [email protected] "tail -50 /var/log/auth.log"
Feb 9 15:58:36 instance-20260202-0125 sshd[93460]: Connection closed by authenticating user root 15.204.243.11 port 54840 [preauth]
Feb 9 15:58:53 instance-20260202-0125 sshd[93463]: Invalid user zabbix from 104.248.81.72 port 43588
Feb 9 15:58:53 instance-20260202-0125 sshd[93463]: Connection closed by invalid user zabbix 104.248.81.72 port 43588 [preauth]
Feb 9 15:58:54 instance-20260202-0125 systemd-logind[720]: Power key pressed.
Feb 9 15:58:54 instance-20260202-0125 systemd-logind[720]: Powering Off...
Feb 9 15:58:55 instance-20260202-0125 systemd-logind[720]: System is powering down.
Feb 9 15:58:55 instance-20260202-0125 sshd[93465]: Invalid user guest from 167.71.0.33 port 37030
Feb 9 15:58:56 instance-20260202-0125 sshd[93465]: Connection closed by invalid user guest 167.71.0.33 port 37030 [preauth]
Feb 9 16:00:23 instance-20260202-0125 sshd[736]: Server listening on 0.0.0.0 port 22.
Feb 9 16:00:23 instance-20260202-0125 sshd[736]: Server listening on :: port 22.
Feb 9 16:00:24 instance-20260202-0125 systemd-logind[715]: New seat seat0.
Feb 9 16:00:24 instance-20260202-0125 systemd-logind[715]: Watching system buttons on /dev/input/event0 (Power Button)
Feb 9 16:00:24 instance-20260202-0125 systemd-logind[715]: Watching system buttons on /dev/input/event1 (Sleep Button)
Feb 9 16:00:24 instance-20260202-0125 systemd-logind[715]: Watching system buttons on /dev/input/event2 (AT Translated Set 2 keyboard)
Feb 9 16:00:40 instance-20260202-0125 sudo: snap_daemon : PWD=/var/snap/oracle-cloud-agent/106 ; USER=root ; COMMAND=/usr/bin/snap refresh --hold oracle-cloud-agent
Feb 9 16:00:40 instance-20260202-0125 sudo: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=584788)
Feb 9 16:00:41 instance-20260202-0125 sudo: pam_unix(sudo:session): session closed for user root
Feb 9 16:01:01 instance-20260202-0125 CRON[1053]: pam_unix(cron:session): session opened for user ubuntu(uid=1001) by (uid=0)
Feb 9 16:01:01 instance-20260202-0125 CRON[1052]: pam_unix(cron:session): session opened for user ubuntu(uid=1001) by (uid=0)
Feb 9 16:01:01 instance-20260202-0125 CRON[1052]: pam_unix(cron:session): session closed for user ubuntu
Feb 9 16:01:01 instance-20260202-0125 CRON[1053]: pam_unix(cron:session): session closed for user ubuntu
Feb 9 16:01:01 instance-20260202-0125 sshd[1050]: Invalid user admin from 104.248.204.244 port 35524
Feb 9 16:01:02 instance-20260202-0125 sshd[1050]: Connection closed by invalid user admin 104.248.204.244 port 35524 [preauth]
Feb 9 16:02:01 instance-20260202-0125 CRON[1058]: pam_unix(cron:session): session opened for user ubuntu(uid=1001) by (uid=0)
Feb 9 16:02:01 instance-20260202-0125 CRON[1059]: pam_unix(cron:session): session opened for user ubuntu(uid=1001) by (uid=0)
Feb 9 16:02:01 instance-20260202-0125 CRON[1059]: pam_unix(cron:session): session closed for user ubuntu
Feb 9 16:02:01 instance-20260202-0125 CRON[1058]: pam_unix(cron:session): session closed for user ubuntu
Feb 9 16:02:06 instance-20260202-0125 sshd[1062]: Invalid user admin from 104.248.204.244 port 60642
Feb 9 16:02:06 instance-20260202-0125 sshd[1062]: Connection closed by invalid user admin 104.248.204.244 port 60642 [preauth]
Feb 9 16:02:50 instance-20260202-0125 login[751]: pam_unix(login:auth): check pass; user unknown
Feb 9 16:02:50 instance-20260202-0125 login[751]: pam_unix(login:auth): authentication failure; logname=LOGIN uid=0 euid=0 tty=/dev/ttyS0 ruser= rhost=
Feb 9 16:02:53 instance-20260202-0125 login[751]: FAILED LOGIN (1) on '/dev/ttyS0' FOR 'UNKNOWN', Authentication failure
Feb 9 16:03:01 instance-20260202-0125 CRON[1065]: pam_unix(cron:session): session opened for user ubuntu(uid=1001) by (uid=0)
Feb 9 16:03:01 instance-20260202-0125 CRON[1064]: pam_unix(cron:session): session opened for user ubuntu(uid=1001) by (uid=0)
Feb 9 16:03:01 instance-20260202-0125 CRON[1064]: pam_unix(cron:session): session closed for user ubuntu
Feb 9 16:03:01 instance-20260202-0125 CRON[1065]: pam_unix(cron:session): session closed for user ubuntu
Feb 9 16:03:04 instance-20260202-0125 sshd[1068]: Invalid user admin from 104.248.204.244 port 40906
Feb 9 16:03:05 instance-20260202-0125 sshd[1068]: Connection closed by invalid user admin 104.248.204.244 port 40906 [preauth]
Feb 9 16:03:31 instance-20260202-0125 sshd[1070]: Invalid user latitude from 80.94.92.186 port 37516
Feb 9 16:03:32 instance-20260202-0125 sshd[1070]: Connection closed by invalid user latitude 80.94.92.186 port 37516 [preauth]
Feb 9 16:03:54 instance-20260202-0125 sshd[1073]: Invalid user admin from 104.248.204.244 port 54788
Feb 9 16:03:55 instance-20260202-0125 sshd[1073]: Connection closed by invalid user admin 104.248.204.244 port 54788 [preauth]
Feb 9 16:04:01 instance-20260202-0125 CRON[1076]: pam_unix(cron:session): session opened for user ubuntu(uid=1001) by (uid=0)
Feb 9 16:04:01 instance-20260202-0125 CRON[1075]: pam_unix(cron:session): session opened for user ubuntu(uid=1001) by (uid=0)
Feb 9 16:04:01 instance-20260202-0125 CRON[1076]: pam_unix(cron:session): session closed for user ubuntu
Feb 9 16:04:01 instance-20260202-0125 CRON[1075]: pam_unix(cron:session): session closed for user ubuntu
Feb 9 16:04:06 instance-20260202-0125 sshd[1079]: Accepted publickey for ubuntu from 222.112.148.16 port 55279 ssh2: RSA SHA256:OiWHPhC0LunRhDbtXT6iX3BRHALX/us1S9sO6rU/k70
Feb 9 16:04:06 instance-20260202-0125 sshd[1079]: pam_unix(sshd:session): session opened for user ubuntu(uid=1001) by (uid=0)
Feb 9 16:04:06 instance-20260202-0125 systemd-logind[715]: New session 9 of user ubuntu.
Feb 9 16:04:06 instance-20260202-0125 systemd: pam_unix(systemd-user:session): session opened for user ubuntu(uid=1001) by (uid=0)
Connection to 134.185.112.18 closed.
인스턴스 접속은 성공
Feb 9 16:04:06 Accepted publickey for ubuntu from 222.112.148.16
Feb 9 16:04:06 pam_unix(sshd:session): session opened for user ubuntu