近期centos 伺服器發生幾次自動關機狀況(halt狀態並非當機)，雖然當場按下電源鍵就可恢復運作，但不解的是查了系統紀錄並未發現當時有user登入狀態卻自動關機，提供一些SYSLOG異常紀錄，煩請各位先進予以指導釋疑，簡述系統狀態如下：
作業系統:CENTOS 5.8
伺服器類型：DNS+MAIL Server
PS.前端有設防火牆，對外僅開啟25.53.110.80 port，並限制特定IP才可SSH連入
/var/log/secure
Jan 11 07:46:30 mail sshd[3041]: Received signal 15; terminating.
重開電源
Jan 11 10:58:11 mail sshd[2932]: Server listening on :: port 22.
Jan 11 10:58:11 mail sshd[2932]: Server listening on 0.0.0.0 port 22.
/var/log/messages
Jan 11 07:45:31 mail named[20250]: network unreachable resolving '98.36.150.62.in-addr.arpa/PTR/IN': 2001:660:3006:1::1:1#53
Jan 11 07:46:27 mail shutdown[4248]: shutting down for system halt
Jan 11 07:46:29 mail smartd[3337]: smartd received signal 15: Terminated
Jan 11 07:46:29 mail smartd[3337]: smartd is exiting (exit status 0)
Jan 11 07:46:30 mail xinetd[3059]: Exiting...
Jan 11 07:46:34 mail named[20250]: shutting down: flushing changes
Jan 11 07:46:34 mail named[20250]: stopping command channel on 127.0.0.1#953
Jan 11 07:46:39 mail exiting on signal 15
電源重開
Jan 11 10:57:50 mail syslogd 1.4.1: restart.
Jan 11 10:57:50 mail kernel: klogd 1.4.1, log source = /proc/kmsg started.
/var/log/maillog
Jan 11 07:45:58 mail dovecot: POP3(systemmanager): Disconnected: Logged out top=0/0, retr=0/0, del=0/21, size=2643110
Jan 11 07:46:04 mail postfix/smtpd[4217]: connect from unknown[108.170.51.126]
Jan 11 07:46:05 mail postfix/smtpd[4217]: NOQUEUE: reject: RCPT from unknown[108.170.51.126]: 554 5.7.1 Service unavailable; Client host [108.170.51.126] blocked using sbl-xbl.spamhaus.org; http://www.spamhaus.org/sbl/query/SBLCSS; from=<cultic@soapnewsletter.in> to=<nyhuskie8@mygo.com> proto=ESMTP helo=<soapnewsletter.in>
Jan 11 07:46:05 mail postfix/smtpd[4217]: disconnect from unknown[108.170.51.126]
Jan 11 07:46:30 mail dovecot: Killed with signal 15
電源重開
Jan 11 10:58:12 mail dovecot: Dovecot v1.0.7 starting up
作業系統:CENTOS 5.8
伺服器類型：DNS+MAIL Server
PS.前端有設防火牆，對外僅開啟25.53.110.80 port，並限制特定IP才可SSH連入
/var/log/secure
Jan 11 07:46:30 mail sshd[3041]: Received signal 15; terminating.
重開電源
Jan 11 10:58:11 mail sshd[2932]: Server listening on :: port 22.
Jan 11 10:58:11 mail sshd[2932]: Server listening on 0.0.0.0 port 22.
/var/log/messages
Jan 11 07:45:31 mail named[20250]: network unreachable resolving '98.36.150.62.in-addr.arpa/PTR/IN': 2001:660:3006:1::1:1#53
Jan 11 07:46:27 mail shutdown[4248]: shutting down for system halt
Jan 11 07:46:29 mail smartd[3337]: smartd received signal 15: Terminated
Jan 11 07:46:29 mail smartd[3337]: smartd is exiting (exit status 0)
Jan 11 07:46:30 mail xinetd[3059]: Exiting...
Jan 11 07:46:34 mail named[20250]: shutting down: flushing changes
Jan 11 07:46:34 mail named[20250]: stopping command channel on 127.0.0.1#953
Jan 11 07:46:39 mail exiting on signal 15
電源重開
Jan 11 10:57:50 mail syslogd 1.4.1: restart.
Jan 11 10:57:50 mail kernel: klogd 1.4.1, log source = /proc/kmsg started.
/var/log/maillog
Jan 11 07:45:58 mail dovecot: POP3(systemmanager): Disconnected: Logged out top=0/0, retr=0/0, del=0/21, size=2643110
Jan 11 07:46:04 mail postfix/smtpd[4217]: connect from unknown[108.170.51.126]
Jan 11 07:46:05 mail postfix/smtpd[4217]: NOQUEUE: reject: RCPT from unknown[108.170.51.126]: 554 5.7.1 Service unavailable; Client host [108.170.51.126] blocked using sbl-xbl.spamhaus.org; http://www.spamhaus.org/sbl/query/SBLCSS; from=<cultic@soapnewsletter.in> to=<nyhuskie8@mygo.com> proto=ESMTP helo=<soapnewsletter.in>
Jan 11 07:46:05 mail postfix/smtpd[4217]: disconnect from unknown[108.170.51.126]
Jan 11 07:46:30 mail dovecot: Killed with signal 15
電源重開
Jan 11 10:58:12 mail dovecot: Dovecot v1.0.7 starting up