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I've been having issues with a very busy machine lately, so I thought I'd look through my logs to see if I could find anything unusual. After looking in /var/log/syslog I've noticed a recurring message
Approximately every 20 minutes, I get this in my syslog (Note: I've replaced my real domain with EXAMPLE.com and my servername with SERVERNAME):
Dec 30 13:00:02 SERVERNAME CRON: (smmsp) CMD (test -x /etc/init.d/sendmail && /usr/share/sendmail/sendmail cron-msp)
Dec 30 13:00:03 SERVERNAME postfix/pickup: EA7D5D9558: uid=106 from=<smmsp>
Dec 30 13:00:04 SERVERNAME postfix/cleanup: EA7D5D9558: message-id=<20111230210003.EA7D5D9558@mail.EXAMPLE.com>
Dec 30 13:00:04 SERVERNAME postfix/qmgr: EA7D5D9558: from=<smmsp@EXAMPLE.com>, size=651, nrcpt=1 (queue active)
Dec 30 13:00:07 SERVERNAME postfix/smtp: EA7D5D9558: to=<root@EXAMPLE.com>, orig_to=<root>, relay=ASPMX.L.GOOGLE.com[209.85.225.$
Dec 30 13:00:07 SERVERNAME postfix/cleanup: 8D9B6D9559: message-id=<20111230210007.8D9B6D9559@mail.EXAMPLE.com>
Dec 30 13:00:07 SERVERNAME postfix/bounce: EA7D5D9558: sender non-delivery notification: 8D9B6D9559
Dec 30 13:00:07 SERVERNAME postfix/qmgr: 8D9B6D9559: from=<>, size=3096, nrcpt=1 (queue active)
Dec 30 13:00:07 SERVERNAME postfix/qmgr: EA7D5D9558: removed
Dec 30 13:00:10 SERVERNAME postfix/smtp: 8D9B6D9559: to=<smmsp@EXAMPLE.com>, relay=ASPMX.L.GOOGLE.com[18.104.22.168]:25, delay=3$
Dec 30 13:00:10 SERVERNAME postfix/qmgr: 8D9B6D9559: removed
Dec 30 13:09:02 SERVERNAME CRON: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ $
I have no idea if this is contributing to my busy machine, but regardless, it seems like this shouldn't be happening. I'm an amateur at the whole cron/postfix business so any comments are appreciated.
From the output it appears that there are cronjjobs configured and they are confired in such a way that cronjob will trigger an email notification to be sent to root users.
By default cronjobs are configured for daily task such as rotating log, clearing packagr archive etc. You can check /etc/cron.daily and /etc/cron.hourly directories to see the list of cronjobs placed in it.
You can also look for the cronjobs that are configured for root user by using the following command: