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Stefan Lasiewski
Asked: 2010-05-01 08:53:39 +0800 CST

Better logging for cronjobs? Send cron output to syslog?

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I am looking for a better way to log cronjobs. Most cronjobs tend to spam email or the console, get ignored, or create yet another logfile.

In this case, I have a Nagios NSCA script which sends data to a central Nagios sever. This send_nsca script also prints a single status line to STDOUT, indicating success or failure.

0 * * * * root    /usr/local/nagios/sbin/nsca_check_disk

This emails the following message to root@localhost, which is then forwarded to my team of sysadmins. Spam.

forwarded nsca_check_disk: 1 data packet(s) sent to host successfully.

I'm looking for a logging method which:

  1. Doesn't spam the messages to email or the console
  2. Don't create yet another krufty logfile which requires cleanup months or years later.
  3. Capture the log information somewhere, so it can be viewed later if desired.
  4. Works on most unixes
  5. Fits into an existing log infrastructure.
  6. Uses common syslog conventions like 'facility' and 'priority'
  7. Can work with third party scripts which don't always do logging internally.
linux logging unix cron syslog

3 Answers

  1. Best Answer

    In the process of writing this question, I answered myself. So I'll answer myself "Jeopardy-style". This expands on the answer provided by Dennis Williamson.

    The following will send any Cron output to /usr/bin/logger (including stderr, which is converted to stdout using 2>&1), which will send to syslog, with a 'tag' of nsca_check_disk. Syslog handles it from there. Since these systems (CentOS and FreeBSD) already have built-in log rotation mechanisms, I don't need to worry about a log like /var/log/mycustom.log filling up a disk.

    */5 * * * * root    /usr/local/nagios/sbin/nsca_check_disk 2>&1 | /usr/bin/logger -t nsca_check_disk

    /var/log/messages now has one additional message which says this:

    Apr 29, 17:40:00 192.168.6.19 nsca_check_disk: 1 data packet(s) sent to host successfully.

    I like /usr/bin/logger , because it works well with an existing syslog configuration and infrastructure, and is included with most Unix distros. Most *nix distributions already do log rotation and do it well.

    • 98

  2. Pipe the output through logger.

    0 * * * * root    /usr/local/nagios/sbin/nsca_check_disk | logger -p local0.notice

    Edit: Your update looks like the right way to go.

    • 7

  3. You can also run crond with option -s (or -S in Busybox) so that output is sent to syslog.

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