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I run several CentOS 4.0 servers, and having to manually check each server for new updates is tedious. To simplify my life, I decided to write a shell script (yumnotifier) to E-mail me when new updates are available. The script (yumnotifier) analyzes the output from ‘yum check-update,’ and generates an E-mail similar to the following if updates are available:

From root@localhost.localdomain Sat Jul 15 19:24:59 2006
Date: Sat, 15 Jul 2006 19:24:59 -0400
From: root
To: matty@localhost.localdomain
Subject: Updates available for biscuit

==== The following updates are available for biscuit ===

comps.i386 2:4.3CENTOS-0.20060314 base
gtk2.i386 2.4.13-18 base
kernel.i686 2.6.9-34.0.2.EL update
libtiff.i386 3.6.1-10 update
mysql.i386 4.1.20-1.RHEL4.1 update
mysql-devel.i386 4.1.20-1.RHEL4.1 update

If you manage systems that use yum, you might be interested in this script.

#!/bin/sh 
#
# Program: E-mail available yum updates <yumnotifier>
#
# Author: Matty < matty91 at gmail dot com >
#
# Current Version: 1.2
#
# Revision History:
#
#  Version 1.2
#    - Removed ! from if statement - John Beaman
#    - Changed comments to reference "yumnotifier", not
#      "yumupdate" -- John Beaman
#
#  Version 1.1
#    - Switched test statement to use "-s" - Luca Rozza
#
#  Version 1.0
#    Initial Release
#
# Last Updated: 10-24-2007
#
# Purpose:
#   yumnotifier checks for updated software package, and E-mails the
#   address defined in the ${ADMIN} variable if updates are available.
#
# License:
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
#
# Installation:
#   Copy the shell script to a suitable location
#
# Usage:
#   To check for new updates each day at midnight, a cron job similar to the
#   following can be used:
#
#   $ crontab -l | grep yumnotifier
#   0 0 * * * /etc/scripts/yumnotifier
#
# Sample output
#   An E-mail similar to the following is sent if updates are available:
#
#   From root@localhost.localdomain  Sat Jul 15 19:24:59 2006
#   Date: Sat, 15 Jul 2006 19:24:59 -0400
#   From: root <root@localhost.localdomain>
#   To: matty@localhost.localdomain
#   Subject: Updates available for biscuit
#  
#   ==== The following updates are available for biscuit ===
#  
#   comps.i386                               2:4.3CENTOS-0.20060314 base            
#   gtk2.i386                                2.4.13-18              base            
#   kernel.i686                              2.6.9-34.0.2.EL        update          
#   libtiff.i386                             3.6.1-10               update          
#   mysql.i386                               4.1.20-1.RHEL4.1       update          
#   mysql-devel.i386                         4.1.20-1.RHEL4.1       update          
#   newt.i386                                0.51.6-7.rhel4         base            
#   php.i386                                 4.3.9-3.15             update          
#   php-ldap.i386                            4.3.9-3.15             update          
#   php-pear.i386                            4.3.9-3.15             update          
#   postgresql-libs.i386                     7.4.13-2.RHEL4.1       update          
#   rpmdb-CentOS.i386                        2:4.3-0.20060314       base            
#   sendmail.i386                            8.13.1-3.RHEL4.5       update          
#   sendmail-cf.i386                         8.13.1-3.RHEL4.5       update          
#   spamassassin.i386                        3.0.6-1.el4            update          
#   vixie-cron.i386                          4:4.1-44.EL4           update          
#   xorg-x11-Mesa-libGL.i386                 6.8.2-1.EL.13.25.1     update          
#   xorg-x11-font-utils.i386                 6.8.2-1.EL.13.25.1     update          
#   xorg-x11-libs.i386                       6.8.2-1.EL.13.25.1     update          
#   xorg-x11-xauth.i386                      6.8.2-1.EL.13.25.1     update          
#   xorg-x11-xfs.i386                        6.8.2-1.EL.13.25.1     update        

PATH=/bin:/usr/bin:/sbin:/usr/sbin
export PATH

# Locations of binaries
GREP="/bin/grep"
HOST=`hostname`
MAIL="/bin/mail"
MKTEMP="/bin/mktemp"
YUM="/usr/bin/yum"

# Who to E-mail with new updates
ADMIN="matty"

if [ ! -f ${YUM} ]
then
        echo "Cannot find ${YUM}"
        exit 1
fi

if [ ! -f ${MKTEMP} ]
then
        echo "Cannot find ${MKTEMP}"
        exit 1
fi

if [ ! -f ${MAIL} ]
then
        echo "Cannot find ${MAIL}"
        exit 1
fi

if [ ! -f ${GREP} ]
then
        echo "Cannot find ${GREP}"
        exit 1
fi

# Dump the yum results to a safe working file
WORK=`${MKTEMP} /tmp/yum.results.XXXXXX`

${YUM} -e0 -d0 check-update > ${WORK}

# If there are updates available, E-mail them
if [ -s ${WORK} ]
then
        REPORT=`${MKTEMP} /tmp/yum.report.XXXXXX`
        echo "==== The following updates are available for ${HOST} ===" > ${REPORT}
        cat ${WORK} >> ${REPORT}
        cat ${REPORT} | ${MAIL} -s "Updates available for ${HOST}" ${ADMIN}
fi

# Cleanup temporary files
rm ${REPORT} ${WORK}

Great script – much better than my last attempt to do this. I made a small change to ignore kernel updates and only send an email if the return code for yum check-update is not zero:

${YUM} -e0 -d0 check-update –exclude=kernel* > ${WORK}

# If there are updates available, E-mail them
if [ $? -ne "0" ]
then
REPORT=`${MKTEMP} /tmp/yum.report.XXXXXX`
echo “==== The following updates are available for ${HOST} ===” > ${REPORT}
cat ${WORK} >> ${REPORT}
cat ${REPORT} | ${MAIL} -s “Updates available for ${HOST}” ${ADMIN}

REFERENCES
http://prefetch.net/blog/index.php/2006/07/16/getting-yum-updates-by-e-mail/
http://prefetch.net/code/yumnotifier