我在 Ubuntu14LTS 服务器上使用 postman 进行 mysql 身份验证时每天都会遇到问题。我认为问题出现在 clamscan scron 因内存不足而中断之后。mysql 套接字在某种程度上中断了，由于 authdaemond 身份验证错误，我无法从电子邮件客户端读取电子邮件，但我可以通过 mysql 命令使用 mysql 数据库，而且我的 webapp 也可以在同一个 mysql 服务器上正常运行。如果我重新启动 mysql 服务，authdaemond 就可以正常工作。
我该如何解决这个问题？任何建议都将不胜感激，谢谢。
错误（日志）
05:06:42 kernel: [449190.488344] Out of memory in UB 56629: OOM killed process 7839 (clamscan) score 0 vm:304480kB, rss:243064kB, swap:0kB
05:06:42 amavis[32693]: (32693-04) (!!)AV: ALL VIRUS SCANNERS FAILED
05:11:15 kernel: [449463.682629] Out of memory in UB 56629: OOM killed process 15307 (clamscan) score 0 vm:362608kB, rss:294436kB, swap:0kB
05:11:15 amavis[32693]: (32693-05-6) (!!)AV: ALL VIRUS SCANNERS FAILED
05:11:53 kernel: [449501.302589] Out of memory in UB 56629: OOM killed process 16511 (clamscan) score 0 vm:374780kB, rss:306480kB, swap:0kB
05:11:53 amavis[32693]: (32693-05-7) (!!)AV: ALL VIRUS SCANNERS FAILED
05:13:43 kernel: [449611.701346] Out of memory in UB 56629: OOM killed process 20750 (clamscan) score 0 vm:377420kB, rss:309408kB, swap:0kB
05:13:43 amavis[32693]: (32693-06-2) (!!)AV: ALL VIRUS SCANNERS FAILED
05:15:27 kernel: [449715.323649] Out of memory in UB 56629: OOM killed process 23783 (clamscan) score 0 vm:374784kB, rss:306516kB, swap:0kB
05:15:27 amavis[32693]: (32693-06-4) (!!)AV: ALL VIRUS SCANNERS FAILED
05:17:36 kernel: [449844.487208] Out of memory in UB 56629: OOM killed process 24521 (clamscan) score 0 vm:378464kB, rss:310460kB, swap:0kB
05:17:36 amavis[32693]: (32693-06-6) (!!)AV: ALL VIRUS SCANNERS FAILED
05:22:09 kernel: [450118.059783] Out of memory in UB 56629: OOM killed process 25385 (clamscan) score 0 vm:380276kB, rss:312244kB, swap:0kB
05:22:09 amavis[32693]: (32693-07-7) (!!)AV: ALL VIRUS SCANNERS FAILED
05:22:39 kernel: [450147.625891] Out of memory in UB 56629: OOM killed process 25389 (clamscan) score 0 vm:378472kB, rss:310460kB, swap:0kB
05:22:39 amavis[32693]: (32693-07-8) (!!)AV: ALL VIRUS SCANNERS FAILED
09:12:59 imapd-ssl: Connection, ip=[::ffff:xx.xx.xx.xx]
09:13:00 authdaemond: failed to connect to mysql server (server=localhost, userid=mail): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
09:13:00 imapd-ssl: LOGIN FAILED, method=PLAIN, ip=[::ffff:xx.xx.xx.xx]
09:13:00 imapd-ssl: authentication error: Input/output error
记忆：
total used free shared buffers cached
Mem: 1024 967 56 67 0 292
-/+ buffers/cache: 674 349
Swap: 128 126 1
过程：
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 sep24 ? 00:00:01 init
root 2 1 0 sep24 ? 00:00:00 [kthreadd/56629]
root 3 2 0 sep24 ? 00:00:00 [khelper/56629]
root 4 2 0 sep24 ? 00:00:00 [rpciod/56629/0]
root 5 2 0 sep24 ? 00:00:00 [rpciod/56629/1]
root 6 2 0 sep24 ? 00:00:00 [rpciod/56629/2]
root 7 2 0 sep24 ? 00:00:00 [rpciod/56629/3]
root 8 2 0 sep24 ? 00:00:00 [rpciod/56629/4]
root 9 2 0 sep24 ? 00:00:00 [rpciod/56629/5]
root 10 2 0 sep24 ? 00:00:00 [rpciod/56629/6]
root 11 2 0 sep24 ? 00:00:00 [rpciod/56629/7]
root 12 2 0 sep24 ? 00:00:00 [nfsiod/56629]
message+ 221 1 0 sep24 ? 00:00:00 dbus-daemon --system --fork
root 249 1 0 sep24 ? 00:00:00 /lib/systemd/systemd-logind
root 252 1 0 sep24 ? 00:00:00 upstart-socket-bridge --daemon
root 253 1 0 sep24 ? 00:00:00 upstart-file-bridge --daemon
root 485 1 0 sep24 ? 00:00:00 /usr/sbin/xinetd -dontfork -pidfile /var/run/xinetd.pid -stayalive -inetd_compat -inetd_ipv6
root 491 1 0 sep24 ? 00:00:00 /usr/sbin/dovecot -F -c /etc/dovecot/dovecot.conf
root 496 1 0 sep24 ? 00:00:00 /usr/sbin/sshd -D
root 498 1 0 sep24 ? 00:00:03 cron
dovecot 541 491 0 sep24 ? 00:00:00 dovecot/anvil
root 542 491 0 sep24 ? 00:00:00 dovecot/log
root 545 491 0 sep24 ? 00:00:00 dovecot/config
syslog 563 1 0 sep24 ? 00:00:01 /sbin/syslogd -u syslog
root 611 1 0 sep24 ? 00:00:00 supervising syslog-ng
root 612 611 0 sep24 ? 00:00:04 /usr/sbin/syslog-ng -p /var/run/syslog-ng.pid --no-caps
amavis 757 1 0 sep24 ? 00:00:08 /usr/sbin/amavisd-new (master)
root 762 1 0 sep24 ? 00:00:46 /usr/sbin/spamd --create-prefs --max-children 5 --helper-home-dir -d --pidfile=/var/run/spamd.pid
root 770 762 0 sep24 ? 00:00:00 spamd child
root 772 762 0 sep24 ? 00:00:00 spamd child
bind 828 1 0 sep24 ? 00:00:00 /usr/sbin/named -u bind
clamav 1199 1 0 sep24 ? 00:00:35 /usr/sbin/clamd
clamav 1323 1 0 sep24 ? 00:02:30 /usr/bin/freshclam -d --quiet
root 1348 1 0 sep24 ? 00:00:00 /usr/sbin/courierlogger -pid=/var/run/courier/authdaemon/pid -start /usr/lib/courier/courier-authlib/authdaemond
root 1349 1348 0 sep24 ? 00:00:00 /usr/lib/courier/courier-authlib/authdaemond
root 1374 1349 0 sep24 ? 00:00:00 /usr/lib/courier/courier-authlib/authdaemond
root 1375 1349 0 sep24 ? 00:00:00 /usr/lib/courier/courier-authlib/authdaemond
root 1376 1349 0 sep24 ? 00:00:00 /usr/lib/courier/courier-authlib/authdaemond
root 1377 1349 0 sep24 ? 00:00:00 /usr/lib/courier/courier-authlib/authdaemond
root 1378 1349 0 sep24 ? 00:00:00 /usr/lib/courier/courier-authlib/authdaemond
root 1381 1 0 sep24 ? 00:00:00 /usr/sbin/courierlogger -pid=/var/run/courier/imapd.pid -start -name=imapd /usr/sbin/couriertcpd -address=0 -maxprocs=40 -maxperip=20 -nodnslookup -noi
root 1382 1381 0 sep24 ? 00:00:00 /usr/sbin/couriertcpd -address=0 -maxprocs=40 -maxperip=20 -nodnslookup -noidentlookup 143 /usr/lib/courier/courier/imaplogin /usr/bin/imapd Maildir
root 1411 1 0 sep24 ? 00:00:00 /usr/sbin/courierlogger -pid=/var/run/courier/imapd-ssl.pid -start -name=imapd-ssl /usr/sbin/couriertcpd -address=0 -maxprocs=40 -maxperip=20 -nodnsloo
root 1412 1411 0 sep24 ? 00:00:00 /usr/sbin/couriertcpd -address=0 -maxprocs=40 -maxperip=20 -nodnslookup -noidentlookup 993 /usr/bin/couriertls -server -tcpd /usr/lib/courier/courier/i
root 1434 1 0 sep24 ? 00:00:00 /usr/sbin/courierlogger -pid=/var/run/courier/pop3d.pid -start -name=pop3d /usr/sbin/couriertcpd -maxprocs=40 -maxperip=4 -nodnslookup -noidentlookup -
root 1435 1434 0 sep24 ? 00:00:00 /usr/sbin/couriertcpd -maxprocs=40 -maxperip=4 -nodnslookup -noidentlookup -address=0 110 /usr/lib/courier/courier/courierpop3login /usr/lib/courier/co
root 1463 1 0 sep24 ? 00:00:00 /usr/sbin/courierlogger -pid=/var/run/courier/pop3d-ssl.pid -start -name=pop3d-ssl /usr/sbin/couriertcpd -address=0 -maxprocs=40 -maxperip=4 -nodnslook
root 1464 1463 0 sep24 ? 00:00:00 /usr/sbin/couriertcpd -address=0 -maxprocs=40 -maxperip=4 -nodnslookup -noidentlookup 995 /usr/bin/couriertls -server -tcpd /usr/lib/courier/courier/co
root 2004 1 0 sep24 ? 00:00:04 /usr/lib/postfix/master
postfix 2009 2004 0 sep24 ? 00:00:02 qmgr -l -t fifo -u
root 2044 1 0 sep24 ? 00:00:00 /usr/sbin/saslauthd -a pam -r -c -m /var/spool/postfix/var/run/saslauthd -n 5
root 2045 2044 0 sep24 ? 00:00:00 /usr/sbin/saslauthd -a pam -r -c -m /var/spool/postfix/var/run/saslauthd -n 5
root 2046 2044 0 sep24 ? 00:00:00 /usr/sbin/saslauthd -a pam -r -c -m /var/spool/postfix/var/run/saslauthd -n 5
root 2047 2044 0 sep24 ? 00:00:00 /usr/sbin/saslauthd -a pam -r -c -m /var/spool/postfix/var/run/saslauthd -n 5
root 2048 2044 0 sep24 ? 00:00:00 /usr/sbin/saslauthd -a pam -r -c -m /var/spool/postfix/var/run/saslauthd -n 5
root 2177 1 0 sep24 tty1 00:00:00 /sbin/getty 38400 console
root 2179 1 0 sep24 tty2 00:00:00 /sbin/getty 38400 tty2
root 2180 1 0 sep24 ? 00:00:00 /sbin/getty -8 38400 tty1
mysql 7612 1 0 12:27 ? 00:01:12 /usr/sbin/mysqld
tomcat7 7703 1 1 12:27 ? 00:03:31 /usr/lib/jvm/default-java/bin/java -Djava.util.logging.config.file=/var/lib/tomcat7/conf/logging.properties -Djava.util.logging.manager=org.apache.juli
root 7812 1 0 12:27 ? 00:00:03 /usr/sbin/apache2 -k start
www-data 7815 7812 0 12:27 ? 00:00:06 /usr/sbin/apache2 -k start
www-data 7816 7812 0 12:27 ? 00:00:06 /usr/sbin/apache2 -k start
www-data 7819 7812 0 12:27 ? 00:00:06 /usr/sbin/apache2 -k start
www-data 7820 7812 0 12:27 ? 00:00:05 /usr/sbin/apache2 -k start
www-data 7821 7812 0 12:27 ? 00:00:05 /usr/sbin/apache2 -k start
www-data 7912 7812 0 12:30 ? 00:00:06 /usr/sbin/apache2 -k start
postfix 16508 2004 0 sep24 ? 00:00:00 tlsmgr -l -t unix -u -c
amavis 24919 757 0 12:40 ? 00:00:02 /usr/sbin/amavisd-new (ch1-avail)
amavis 24921 757 0 12:40 ? 00:00:03 /usr/sbin/amavisd-new (ch1-avail)
www-data 25335 7812 0 13:53 ? 00:00:03 /usr/sbin/apache2 -k start
www-data 25337 7812 0 13:53 ? 00:00:04 /usr/sbin/apache2 -k start
www-data 25338 7812 0 13:53 ? 00:00:03 /usr/sbin/apache2 -k start
postfix 26111 2004 0 16:40 ? 00:00:00 pickup -l -t fifo -u -c -o content_filter= -o receive_override_options=no_header_body_checks
root 26151 496 0 16:53 ? 00:00:00 sshd: root@pts/1
root 26202 26151 0 16:54 pts/1 00:00:00 -bash
postfix 26237 2004 0 16:55 ? 00:00:00 cleanup -z -t unix -u -c
postfix 26238 2004 0 16:55 ? 00:00:00 trivial-rewrite -n rewrite -t unix -u -c
postfix 26241 2004 0 16:55 ? 00:00:00 smtp -t unix -u -c
postfix 26251 2004 0 16:55 ? 00:00:00 bounce -z -t unix -u -c
postfix 26252 2004 0 16:55 ? 00:00:00 bounce -z -t unix -u -c
root 26280 26202 0 16:56 pts/1 00:00:00 ps -ef