Yum provides a very useful package called
yum-cron, its most publicized feature is the ability to enable yum to run nightly cron scheduled packages upgrades.
I honestly don’t really think it is a good idea at all to let the system manage updates by himself but yum-cron can be used for another bunch of tasks, the most interesting one being: send an email if there are updates available.
yum install yum-cron
Configuration is actually pretty simple.
cat /etc/sysconfig/yum-cron --- # Pass any given paramter to yum, as run in all the scripts invoked # by this package. Be aware that this is global, and yum is invoked in # several modes by these scripts for which your own parameter might not # be appropriate YUM_PARAMETER= # Don't install, just check (valid: yes|no) CHECK_ONLY=yes # Check to see if you can reach the repos before updating (valid: yes|no) CHECK_FIRST=no # Don't install, just check and download (valid: yes|no) # Implies CHECK_ONLY=yes (gotta check first to see what to download) DOWNLOAD_ONLY=no # Error level, practical range 0-10, 0 means print only critical errors which # you must be told, 1 means print all errors, even ones that are not important # Level 0 is the default # ERROR_LEVEL=0 # Debug level, practical range 0-10, higher number means more output # Level 1 is a useful level if you want to see what's been done and # don't want to read /var/log/yum.log # Level 0 is the default # DEBUG_LEVEL=1 # randomwait is used by yum to wait random time # default is 60 so yum waits random time from 1 to 60 minutes # the value must not be zero RANDOMWAIT="60" # if MAILTO is set and the mail command is available, the mail command # is used to deliver yum output # by default MAILTO is unset, so crond mails the output by itself # example: MAILTO=root MAILTO=root # you may set SYSTEMNAME if you want your yum emails tagged differently # default is output of hostname command # this variable is used only if MAILTO is set too SYSTEMNAME="uwot.eu" # you may set DAYS_OF_WEEK to the days of the week you want to run # default is every day DAYS_OF_WEEK="0123456" # which day should it do cleanup on? defaults to 0 (Sunday). If this day isn't in the # DAYS_OF_WEEK above, it'll never happen CLEANDAY="0123456" # set to yes to make the yum-cron service to wait for transactions to complete SERVICE_WAITS=yes # set maximum time period (in seconds) for the yum-cron service to wait for # transactions to complete. The default is 300 seconds (5 minutes) SERVICE_WAIT_TIME=300
CHECK_ONLY parameter is what makes yum-cron just check for updates and report back via email without installing anything.
Everything else is pretty much straightforward, for more information
yum-cron is managed like every other service with