Delivering cron and logwatch emails to gmail in RHEL

One of my servers has no real DNS name, there is no MX record and I can hardly confiture postfix for e-mail delivery. While relaying e-mails to another SMTP server is an option, it’s actually not needed to configure MTA in order to get emails delivered from cron and logwatch. One can use MUA called mailx to do the job.

The goal is to avoid more complex configuration of postfix or (jeeeez) sendmail, so this is an alternative approach. I am not telling you this is the best thing you should do. It just works for few of my Linux servers. This will work both on RHEL6 and RHEL7 and probably even older or newer versions. And of course CentOS as well.

Vixie cron, the default cron in RHEL, uses sendmail command for all emails. This is actually part of postfix package, delivery is handled by the MTA which I actually wanted to avoid. In this tutorial, we will configure vixie cron in RHEL7 to send e-mails via mailx user agent. First of all, get mailx installed:

# yum -y install mailx

Then edit either /etc/mail.rc or /root/.mailrc as follows:

# cat /root/.mailrc
set name="Server1234"
set from=""
set smtp=smtps://
set smtp-auth=login
set smtp-auth-password=mysecretpassword
set ssl-verify=ignore
set nss-config-dir=/etc/pki/nssdb

Make sure that from address is same as smtp-auth-user address, gmail servers will insist on this. Server certificate is ignored, you may want to install it into the NSS database. We are ready to send a test e-mail:

# mailx -r
Subject: Test

This is a test

There will be a warning on the standard error about unkonwn certificate. I suggest to put google server CA into the NSS database, but it’s harmless and you can keep it as is if you don’t mind man-in-the-middle.

Error in certificate: Peer's certificate issuer is not recognized.

Now, create a wrapper script that will explicitly set from and to addresses:

# cat /usr/local/sbin/mailx-r
exec mailx -r

Make sure the script is executable. Finally, set it via crond command line option:

# cat /etc/sysconfig/crond
CRONDARGS="-m /usr/local/sbin/mailx-r"

And restart crond:

# service crond restart

You are now receiving e-mails from cron, congratulations. The next step I usually do is installing logwatch. Since it also uses sendmail we want to disable it and run it manually from our own cron script feeding the output to the mailx command:

# yum -y install logwatch

Disable the built-in daily report because this one uses sendmail. While it could be possible to change this via some configuration option, I actually like my very own cron script.

# cat /etc/logwatch/conf/logwatch.conf
DailyReport = no

Now, create your own script and feed the output into mailx. For a weekly report do something like:

# cat /etc/cron.weekly/logwatch
logwatch --print --range 'between -7 days and today' | mailx -s "Logwatch from XYZ" -r 2>/dev/null

For a daily report do this:

# cat /etc/cron.daily/logwatch
logwatch --print --range yesterday | mailx -s "Logwatch from XYZ" -r 2>/dev/null

Make sure the cron script is executable and test it first. That’s all, enjoy all the e-mails!

19 September 2018 | linux | fedora | rhel