One thing that hopefully will shine some light into why this is happening, would be the syslog. You can either access it via the GUI: <node> -> System -> Syslogs or directly at /var/log/syslog.
Check the times when the VM is rebooted. Do you have HA enabled?
Hi, Thank you for your reply.
The issue happened today at 2.45 PM again.
I check the log but can not find any reason for restarting.
Aug 09 14:43:26 node001 sshd[4089]: Received disconnect from 10.10.10.1 port 10590:11: [preauth]
Aug 09 14:43:26 node001 sshd[4089]: Disconnected from authenticating user root 10.10.10.1 port 10590 [preauth]
Aug 09 14:43:26 node001 sshd[4089]: PAM 2 more authentication failures; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:43:53 node001 sshd[16616]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:43:56 node001 sshd[16616]: Failed password for root from 10.10.10.1 port 62220 ssh2
Aug 09 14:43:58 node001 sshd[16616]: Received disconnect from 10.10.10.1 port 62220:11: Bye Bye [preauth]
Aug 09 14:43:58 node001 sshd[16616]: Disconnected from authenticating user root 10.10.10.1 port 62220 [preauth]
Aug 09 14:44:00 node001 systemd[1]: Starting Proxmox VE replication runner...
Aug 09 14:44:01 node001 systemd[1]: pvesr.service: Succeeded.
Aug 09 14:44:01 node001 systemd[1]: Started Proxmox VE replication runner.
Aug 09 14:44:01 node001 sshd[18889]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:44:03 node001 sshd[18889]: Failed password for root from 10.10.10.1 port 50180 ssh2
Aug 09 14:44:05 node001 sshd[18889]: Received disconnect from 10.10.10.1 port 50180:11: Bye Bye [preauth]
Aug 09 14:44:05 node001 sshd[18889]: Disconnected from authenticating user root 10.10.10.1 port 50180 [preauth]
Aug 09 14:44:09 node001 sshd[20608]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:44:12 node001 sshd[20608]: Failed password for root from 10.10.10.1 port 53990 ssh2
Aug 09 14:44:13 node001 sshd[20608]: Received disconnect from 10.10.10.1 port 53990:11: Normal Shutdown, Thank you for playing [preauth]
Aug 09 14:44:13 node001 sshd[20608]: Disconnected from authenticating user root 10.10.10.1 port 53990 [preauth]
Aug 09 14:44:50 node001 sshd[26672]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:44:52 node001 sshd[26672]: Failed password for root from 10.10.10.1 port 58392 ssh2
Aug 09 14:44:55 node001 sshd[26672]: Received disconnect from 10.10.10.1 port 58392:11: Bye Bye [preauth]
Aug 09 14:44:55 node001 sshd[26672]: Disconnected from authenticating user root 10.10.10.1 port 58392 [preauth]
Aug 09 14:45:00 node001 systemd[1]: Starting Proxmox VE replication runner...
Aug 09 14:45:01 node001 systemd[1]: pvesr.service: Succeeded.
Aug 09 14:45:01 node001 systemd[1]: Started Proxmox VE replication runner.
Aug 09 14:45:01 node001 CRON[28611]: pam_unix(cron:session): session opened for user root by (uid=0)
Aug 09 14:45:01 node001 CRON[28612]: pam_unix(cron:session): session opened for user root by (uid=0)
Aug 09 14:45:01 node001 CRON[28613]: pam_unix(cron:session): session opened for user root by (uid=0)
Aug 09 14:45:03 node001 zed[28823]: eid=55829 class=history_event pool_guid=0x5BF16353E1ED7029
Aug 09 14:45:15 node001 sshd[29197]: Invalid user yushu from 10.10.10.1 port 43634
Aug 09 14:45:15 node001 sshd[29197]: pam_unix(sshd:auth): check pass; user unknown
Aug 09 14:45:15 node001 sshd[29197]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1
Aug 09 14:45:17 node001 sshd[29197]: Failed password for invalid user yushu from 10.10.10.1 port 43634 ssh2
Aug 09 14:45:17 node001 sshd[29197]: Received disconnect from 10.10.10.1 port 43634:11: Bye Bye [preauth]
Aug 09 14:45:17 node001 sshd[29197]: Disconnected from invalid user yushu 10.10.10.1 port 43634 [preauth]
Aug 09 14:45:22 node001 sshd[32033]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:45:24 node001 sshd[32033]: Failed password for root from 10.10.10.1 port 54108 ssh2
Aug 09 14:45:25 node001 sshd[32217]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:45:26 node001 sshd[32033]: Received disconnect from 10.10.10.1 port 54108:11: Normal Shutdown, Thank you for playing [preauth]
Aug 09 14:45:26 node001 sshd[32033]: Disconnected from authenticating user root 10.10.10.1 port 54108 [preauth]
Aug 09 14:45:26 node001 pveproxy[18573]: worker exit
Aug 09 14:45:26 node001 pveproxy[6917]: worker 18573 finished
Aug 09 14:45:26 node001 pveproxy[6917]: starting 1 worker(s)
Aug 09 14:45:26 node001 pveproxy[6917]: worker 32715 started
Aug 09 14:45:27 node001 sshd[32217]: Failed password for root from 10.10.10.1 port 43292 ssh2
Aug 09 14:45:27 node001 sshd[32217]: Received disconnect from 10.10.10.1 port 43292:11: Bye Bye [preauth]
Aug 09 14:45:27 node001 sshd[32217]: Disconnected from authenticating user root 10.10.10.1 port 43292 [preauth]
Aug 09 14:45:29 node001 sshd[32723]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:45:31 node001 sshd[32723]: Failed password for root from 10.10.10.1 port 37176 ssh2
Aug 09 14:45:33 node001 sshd[32723]: Received disconnect from 10.10.10.1 port 37176:11: Bye Bye [preauth]
Aug 09 14:45:33 node001 sshd[32723]: Disconnected from authenticating user root 10.10.10.1 port 37176 [preauth]
Aug 09 14:45:40 node001 sshd[35210]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:45:42 node001 sshd[35210]: Failed password for root from 10.10.10.1 port 48161 ssh2
Aug 09 14:45:47 node001 sshd[35210]: Failed password for root from 10.10.10.1 port 48161 ssh2
Aug 09 14:45:51 node001 sshd[35210]: Failed password for root from 10.10.10.1 port 48161 ssh2
Aug 09 14:45:53 node001 sshd[35210]: Received disconnect from 10.10.10.1 port 48161:11: [preauth]
Aug 09 14:45:53 node001 sshd[35210]: Disconnected from authenticating user root 10.10.10.1 port 48161 [preauth]
Aug 09 14:45:53 node001 sshd[35210]: PAM 2 more authentication failures; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:46:00 node001 systemd[1]: Starting Proxmox VE replication runner...
Aug 09 14:46:01 node001 systemd[1]: pvesr.service: Succeeded.
Aug 09 14:46:01 node001 systemd[1]: Started Proxmox VE replication runner.
Aug 09 14:46:12 node001 zed[4293]: eid=55830 class=history_event pool_guid=0x5BF16353E1ED7029
Aug 09 14:46:12 node001 CRON[28612]: pam_unix(cron:session): session closed for user root
Aug 09 14:46:13 node001 zed[4554]: eid=55831 class=history_event pool_guid=0x5BF16353E1ED7029
Aug 09 14:46:26 node001 sshd[5860]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:46:28 node001 sshd[5860]: Failed password for root from 10.10.10.1 port 23849 ssh2
Aug 09 14:46:29 node001 sshd[6340]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:46:31 node001 sshd[5860]: Failed password for root from 10.10.10.1 port 23849 ssh2
Aug 09 14:46:31 node001 sshd[6340]: Failed password for root from 10.10.10.1 port 54228 ssh2
Aug 09 14:46:33 node001 sshd[6340]: Received disconnect from 10.10.10.1 port 54228:11: Normal Shutdown, Thank you for playing [preauth]
Aug 09 14:46:33 node001 sshd[6340]: Disconnected from authenticating user root 10.10.10.1 port 54228 [preauth]
Aug 09 14:46:34 node001 sshd[5860]: Received disconnect from 10.10.10.1 port 23849:11: [preauth]
Aug 09 14:46:34 node001 sshd[5860]: Disconnected from authenticating user root 10.10.10.1 port 23849 [preauth]
Aug 09 14:46:34 node001 sshd[5860]: PAM 1 more authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:46:41 node001 sshd[6694]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=root
Aug 09 14:46:43 node001 sshd[6694]: Failed password for root from 10.10.10.1 port 35297 ssh2
Aug 09 14:46:46 node001 sshd[7880]: Invalid user sinus2 from 10.10.10.1 port 43524
Aug 09 14:46:46 node001 sshd[7880]: pam_unix(sshd:auth): check pass; user unknown
Aug 09 14:46:46 node001 sshd[7880]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1
Aug 09 14:46:47 node001 sshd[6694]: Failed password for root from 10.10.10.1 port 35297 ssh2
Aug 09 14:46:48 node001 sshd[7880]: Failed password for invalid user sinus2 from 10.10.10.1 port 43524 ssh2
Aug 09 14:46:50 node001 sshd[7880]: Received disconnect from 10.10.10.1 port 43524:11: Bye Bye [preauth]
Aug 09 14:46:50 node001 sshd[7880]: Disconnected from invalid user sinus2 10.10.10.1 port 43524 [preauth]
Aug 09 14:46:50 node001 sshd[8105]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=10.10.10.1 user=roo
