Automatic nightly YUM updates with yum-cron

Recent Linux security vulnerabilities and updates such as the bash exploit (shellshock) have highlighted the need to keep your Linux operating system's packages up to date. So it's a good idea to have in place an automatic nightly cron job which runs YUM updates.

You can do nightly YUM updates automatically with email notifications via a package called yum-cron.

How to install yum-cron ?

---

To install yum-cron and setup email notifications run in SSH window:

Code:

yum -y install yum-cron
chkconfig yum-cron on

Then edit /etc/sysconfig/yum-cron (CentOS 6) to set MAILTO= email address or /etc/yum/yum-cron.conf (CentOS 7) to set email_to= for email notifications. If you use pushover.net for notifications to your mobile or tablet device, you can set

For CentOS 6

Code:

MAILTO=yourUSERkey+devicename+p1@api.pushover.net

For CentOS 7

Code:

email_to=yourUSERkey+devicename+p1@api.pushover.net

For CentOS 7 whether or not if updates are applied are controlled by 3 variables in /etc/yum/yum-cron.conf or /etc/yum/yum-cron-hourly.conf both have the 3 variables disabled = no by default. Need to change them to yes

Code:

# Whether a message should emitted when updates are available.
update_messages = no

# Whether updates should be downloaded when they are available. Note
# that updates_messages must also be yes for updates to be downloaded.
download_updates = no

# Whether updates should be applied when they are available.  Note
# that both update_messages and download_updates must also be yes for
# the update to be applied
apply_updates = no

Also for CentOS 7,
messages either go to stdio or email, default is stdio so for emails set emit_via = email

Code:

# How to send messages.  Valid options are stdio and email.  If
# emit_via includes stdio, messages will be sent to stdout; this is useful
# to have cron send the messages.  If emit_via includes email, this
# program will send email itself according to the configured options.
# If emit_via is None or left blank, no messages will be sent.
emit_via = stdio

For CentOS 7, using sed replacements to enable yum-cron settings. This sets daily updates for full yum upgrades and hourly to security only updates.

Code:

    EMAIL=your@email.com
    sed -i "s|^email_to = root|email_to = ${EMAIL}|" /etc/yum/yum-cron.conf
    sed -i 's|^update_messages = no|update_messages = yes|' /etc/yum/yum-cron.conf
    sed -i 's|^download_updates = no|download_updates = yes|' /etc/yum/yum-cron.conf
    sed -i 's|^apply_updates = no|apply_updates = yes|' /etc/yum/yum-cron.conf
    sed -i 's|^emit_via = stdio|emit_via = email|' /etc/yum/yum-cron.conf

    sed -i "s|^email_to = root|email_to = ${EMAIL}|" /etc/yum/yum-cron-hourly.conf
    sed -i 's|^update_cmd = default|update_cmd = security|' /etc/yum/yum-cron-hourly.conf
    sed -i 's|^update_messages = no|update_messages = yes|' /etc/yum/yum-cron-hourly.conf
    sed -i 's|^download_updates = no|download_updates = yes|' /etc/yum/yum-cron-hourly.conf
    sed -i 's|^apply_updates = no|apply_updates = yes|' /etc/yum/yum-cron-hourly.conf
    sed -i 's|^emit_via = stdio|emit_via = email|' /etc/yum/yum-cron-hourly.conf   

    egrep '^email_to|^update_messages|^download_updates|^apply_updates|^emit_via' /etc/yum/yum-cron.conf
    egrep '^email_to|^update_cmd|^update_messages|^download_updates|^apply_updates|^emit_via' /etc/yum/yum-cron-hourly.conf
    service yum-cron restart

For CentOS 7 also has an hourly configuration file at /etc/yum/yum-cron-hourly.conf

Spoiler: contents of yum-cron-hourly.conf

Code:

[commands]
#  What kind of update to use:
# default                            = yum upgrade
# security                           = yum --security upgrade
# security-severity:Critical         = yum --sec-severity=Critical upgrade
# minimal                            = yum --bugfix upgrade-minimal
# minimal-security                   = yum --security upgrade-minimal
# minimal-security-severity:Critical =  --sec-severity=Critical upgrade-minimal
update_cmd = default

# Whether a message should emitted when updates are available.
update_messages = no

# Whether updates should be downloaded when they are available. Note
# that updates_messages must also be yes for updates to be downloaded.
download_updates = no

# Whether updates should be applied when they are available.  Note
# that both update_messages and download_updates must also be yes for
# the update to be applied
apply_updates = no

# Maximum amout of time to randomly sleep, in minutes.  The program
# will sleep for a random amount of time between 0 and random_sleep
# minutes before running.  This is useful for e.g. staggering the
# times that multiple systems will access update servers.  If
# random_sleep is 0 or negative, the program will run immediately.
random_sleep = 15


[emitters]
# Name to use for this system in messages that are emitted.  If
# system_name is None, the hostname will be used.
system_name = None

# How to send messages.  Valid options are stdio and email.  If
# emit_via includes stdio, messages will be sent to stdout; this is useful
# to have cron send the messages.  If emit_via includes email, this
# program will send email itself according to the configured options.
# If emit_via is None or left blank, no messages will be sent.
emit_via = stdio

# The width, in characters, that messages that are emitted should be
# formatted to.
ouput_width = 80


[email]
# The address to send email messages from.
email_from = root

# List of addresses to send messages to.
email_to = root

# Name of the host to connect to to send email messages.
email_host = localhost


[groups]
# List of groups to update
group_list = None

# The types of group packages to install
group_package_types = mandatory, default

[base]
# This section overrides yum.conf

# Use this to filter Yum core messages
# -4: critical
# -3: critical+errors
# -2: critical+errors+warnings (default)
debuglevel = -2

# skip_broken = True
mdpolicy = group:main

# Uncomment to auto-import new gpg keys (dangerous)
# assumeyes = True

Then start the yum-cron service

Code:

service yum-cron start

sample /etc/sysconfig/yum-cron where I have set MAILTO to my pushover.net email address - yourUSERkey+devicename+p1@api.pushover.net so I get notifications to my mobile and tablet devices (a tip that @Matt posted about that keeps on giving ) and set the system name different from actual hostname of the server so I can more easily identify it among my 25+ servers, SYSTEMNAME="vultrol65".

This is for my Vulr 768MB VPS running Oracle Linux 6.5 and Centmin Mod .08 beta and which just got auto yum-cron updated to MariaDB 10.0.14 MySQL version along with other YUM package updates.

Code:

# 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=no

# 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=yourUSERkey+devicename+p1@api.pushover.net

# 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="vultrol65"

# 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="0"

# 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

Code:

mysqladmin ver
mysqladmin  Ver 9.1 Distrib 10.0.14-MariaDB, for Linux on x86_64
Copyright (c) 2000, 2014, Oracle, SkySQL Ab and others.

Server version          10.0.14-MariaDB
Protocol version        10
Connection              Localhost via UNIX socket
UNIX socket             /var/lib/mysql/mysql.sock
Uptime:                 1 hour 48 min 10 sec

Code:

tail -50 /var/log/yum.log | grep 'Sep 27'; date

Sep 27 05:21:26 Updated: nss-util-3.16.1-2.el6_5.x86_64
Sep 27 05:21:26 Updated: nss-softokn-freebl-3.14.3-12.el6_5.x86_64
Sep 27 05:21:26 Updated: nss-softokn-3.14.3-12.el6_5.x86_64
Sep 27 05:21:26 Updated: nss-3.16.1-7.0.1.el6_5.x86_64
Sep 27 05:21:26 Updated: nss-sysinit-3.16.1-7.0.1.el6_5.x86_64
Sep 27 05:21:26 Updated: MariaDB-common-10.0.14-1.el6.x86_64
Sep 27 05:21:27 Updated: MariaDB-compat-10.0.14-1.el6.x86_64
Sep 27 05:21:28 Updated: MariaDB-client-10.0.14-1.el6.x86_64
Sep 27 05:21:35 Updated: MariaDB-server-10.0.14-1.el6.x86_64
Sep 27 05:21:35 Updated: MariaDB-shared-10.0.14-1.el6.x86_64
Sep 27 05:21:37 Updated: MariaDB-devel-10.0.14-1.el6.x86_64
Sep 27 05:21:37 Updated: nss-tools-3.16.1-7.0.1.el6_5.x86_64
Sat Sep 27 07:13:26 PDT 2014

Code:

yum list installed MariaDB* -q
Installed Packages
MariaDB-client.x86_64                                                           10.0.14-1.el6                                                           @mariadb
MariaDB-common.x86_64                                                           10.0.14-1.el6                                                           @mariadb
MariaDB-compat.x86_64                                                           10.0.14-1.el6                                                           @mariadb
MariaDB-devel.x86_64                                                            10.0.14-1.el6                                                           @mariadb
MariaDB-server.x86_64                                                           10.0.14-1.el6                                                           @mariadb
MariaDB-shared.x86_64                                                           10.0.14-1.el6                                                           @mariadb

Screenshots from my Pushover client on mobile. As you can see I use pushover.net notifications for my forum's automatic backup script for forum files, database (schema, data and grants) which backups up every 8 hours + Linode's daily backups as well for Linux Malware Detect (maldet) + ClamAV scanner notifications and for yum-cron notifications for all my servers now including my new SoYouStart server

Verifying yum-cron is working

You can check your cron log at /var/log/cron to see if it ran

Code:

grep yum.cron /var/log/cron | tail -10
Sep 29 03:24:01 vultr run-parts(/etc/cron.daily)[21165]: starting 0yum.cron
Sep 29 03:28:39 vultr run-parts(/etc/cron.daily)[21235]: finished 0yum.cron
Sep 30 04:45:01 vultr run-parts(/etc/cron.daily)[26324]: starting 0yum.cron
Sep 30 04:54:00 vultr run-parts(/etc/cron.daily)[26403]: finished 0yum.cron
Oct  1 03:39:01 vultr run-parts(/etc/cron.daily)[31068]: starting 0yum.cron
Oct  1 04:29:19 vultr run-parts(/etc/cron.daily)[31314]: finished 0yum.cron

and check yum log when it does notify of updates

Code:

tail -10 /var/log/yum.log
Sep 27 04:08:45 Updated: nss-util-3.16.1-2.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-softokn-freebl-3.14.3-12.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-softokn-3.14.3-12.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-sysinit-3.16.1-7.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-3.16.1-7.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-tools-3.16.1-7.el6_5.x86_64
Oct 01 04:29:18 Updated: 1:net-snmp-libs-5.5-49.el6_5.4.x86_64
Oct 01 04:29:18 Updated: 1:net-snmp-5.5-49.el6_5.4.x86_64
Oct 01 04:29:18 Updated: 1:net-snmp-utils-5.5-49.el6_5.4.x86_64
Oct 01 04:29:18 Updated: 1:net-snmp-devel-5.5-49.el6_5.4.x86_64

 

yeah I haven't really experienced any YUM updates which would negatively impact a system much at all

maybe could exclude some packages from update i.e. kernel

Code:

YUM_PARAMETER="-x kernel*" 

 

Custom compilled RPM packages ? or you mean source compiled ? if it's custom RPM packages via a repo, couldn't you just define --disablerepo=customreponame in YUM_PARAMETER ? Guess it would be nice if yum-cron could do multiple profiles for different yum repos.

 

yum excludes for htop and php would be easier then

ah yum-cron is just a shell script at /etc/cron.daily/0yum.cron - could play with it

i.e. create a second config file using a copy of /etc/sysconfig/yum-cron and second cronjob copy of /etc/cron.daily/0yum.cron for a different yum-cron profile ? So main yum-cron could have some packages excluded for updates and second yum-cron profile would have it for download or is available update notifications.

Looks like you'd need separate copy of /etc/init.d/yum-cron startup script and for

Code:

LOCKDIR=/var/lock/yum-cron.lock
LOCKFILE=$LOCKDIR/pidfile
TSLOCK=$LOCKDIR/ts.lock

Code:

#!/bin/bash

# Only run if this flag file is set (by /etc/rc.d/init.d/yum-cron)
if [ ! -f /var/lock/subsys/yum-cron ]; then
  exit 0
fi

DAILYSCRIPT=/etc/yum/yum-daily.yum
WEEKLYSCRIPT=/etc/yum/yum-weekly.yum
LOCKDIR=/var/lock/yum-cron.lock
LOCKFILE=$LOCKDIR/pidfile
TSLOCK=$LOCKDIR/ts.lock

# Grab config settings
if [ -f /etc/sysconfig/yum-cron ]; then
  source /etc/sysconfig/yum-cron
fi
# set default for SYSTEMNAME
[ -z "$SYSTEMNAME" ]  && SYSTEMNAME=$(hostname)

# Only run on certain days of the week
dow=`date +%w`
DAYS_OF_WEEK=${DAYS_OF_WEEK:-0123456}
if [ "${DAYS_OF_WEEK/$dow/}" == "${DAYS_OF_WEEK}" ]; then
  exit 0
fi

# if DOWNLOAD_ONLY is set then we force CHECK_ONLY too.
# Gotta check before one can download!
if [ "$DOWNLOAD_ONLY" == "yes" ]; then
  CHECK_ONLY=yes
fi

YUMTMP=$(mktemp /var/run/yum-cron.XXXXXX)
touch $YUMTMP
[ -x /sbin/restorecon ] && /sbin/restorecon $YUMTMP

# Random wait function
random_wait() {
  sleep $(( $RANDOM % ($RANDOMWAIT * 60) + 1 ))
}

# Note - the lockfile code doesn't try and use YUMTMP to email messages nicely.
# Too many ways to die, this gets handled by normal cron error mailing.
# Try mkdir for the lockfile, will test for and make it in one atomic action
if mkdir $LOCKDIR 2>/dev/null; then
  # store the current process ID in there so we can check for staleness later
  echo "$$" >"${LOCKFILE}"
  # and clean up locks and tempfile if the script exits or is killed
  trap "{ rm -f $LOCKFILE $TSLOCK; rmdir $LOCKDIR 2>/dev/null; rm -f $YUMTMP; exit 255; }" INT TERM EXIT
else
  # lock failed, check if process exists.  First, if there's no PID file
  # in the lock directory, something bad has happened, we can't know the
  # process name, so clean up the old lockdir and restart
  if [ ! -f $LOCKFILE ]; then
    rmdir $LOCKDIR 2>/dev/null
    echo "yum-cron: no lock PID, clearing and restarting myself" >&2
    exec $0 "$@"
  fi
  OTHERPID="$(cat "${LOCKFILE}")"
  # if cat wasn't able to read the file anymore, another instance probably is
  # about to remove the lock -- exit, we're *still* locked
    if [ $? != 0 ]; then
      echo "yum-cron: lock failed, PID ${OTHERPID} is active" >&2
      exit 0
    fi
    if ! kill -0 $OTHERPID &>/dev/null; then
      # lock is stale, remove it and restart
      echo "yum-cron: removing stale lock of nonexistant PID ${OTHERPID}" >&2
      rm -rf "${LOCKDIR}"
      echo "yum-cron: restarting myself" >&2
      exec $0 "$@"
    else
      # Remove stale (more than a day old) lockfiles
      find $LOCKDIR -type f -name 'pidfile' -amin +1440 -exec rm -rf $LOCKDIR \;
      # if it's still there, it wasn't too old, bail
      if [ -f $LOCKFILE ]; then
        # lock is valid and OTHERPID is active - exit, we're locked!
        echo "yum-cron: lock failed, PID ${OTHERPID} is active" >&2
        exit 0
      else
        # lock was invalid, restart
        echo "yum-cron: removing stale lock belonging to stale PID ${OTHERPID}" >&2
        echo "yum-cron: restarting myself" >&2
        exec $0 "$@"
      fi
    fi
fi

# Then check for updates and/or do them, as configured
{
  # First, if this is CLEANDAY, do so
  CLEANDAY=${CLEANDAY:-0}
  if [ ! "${CLEANDAY/$dow/}" == "${CLEANDAY}" ]; then
      /usr/bin/yum $YUM_PARAMETER -e ${ERROR_LEVEL:-0} -d ${DEBUG_LEVEL:-0} -y shell $WEEKLYSCRIPT
  fi

  # Now continue to do the real work
  if [ "$CHECK_ONLY" == "yes" ]; then
    random_wait
    touch $TSLOCK
    /usr/bin/yum $YUM_PARAMETER -e 0 -d 0 -y check-update 1> /dev/null 2>&1
    case $? in
      1)   exit 1;;
      100) echo "New updates available for host `/bin/hostname`";
           /usr/bin/yum $YUM_PARAMETER -e ${ERROR_LEVEL:-0} -d ${DEBUG_LEVEL:-0} -y -C check-update
           if [ "$DOWNLOAD_ONLY" == "yes" ]; then
               /usr/bin/yum $YUM_PARAMETER -e ${ERROR_LEVEL:-0} -d ${DEBUG_LEVEL:-0} -y --downloadonly update
               echo "Updates downloaded, use \"yum -C update\" manually to install them."
           fi
           ;;
    esac
  elif [ "$CHECK_FIRST" == "yes" ]; then
    # Don't run if we can't access the repos
    random_wait
    touch $TSLOCK
    /usr/bin/yum $YUM_PARAMETER -e 0 -d 0 check-update 2>&-
    case $? in
      1)   exit 1;;
      100) /usr/bin/yum $YUM_PARAMETER -e ${ERROR_LEVEL:-0} -d ${DEBUG_LEVEL:-0} -y update yum
           /usr/bin/yum $YUM_PARAMETER -e ${ERROR_LEVEL:-0} -d ${DEBUG_LEVEL:-0} -y shell $DAILYSCRIPT
           ;;
    esac
  else
    random_wait
    touch $TSLOCK
    /usr/bin/yum $YUM_PARAMETER -e ${ERROR_LEVEL:-0} -d ${DEBUG_LEVEL:-0} -y update yum
    /usr/bin/yum $YUM_PARAMETER -e ${ERROR_LEVEL:-0} -d ${DEBUG_LEVEL:-0} -y shell $DAILYSCRIPT
  fi
} >> $YUMTMP 2>&1

if [ ! -z "$MAILTO" ] && [ -x /bin/mail ]; then
# if MAILTO is set, use mail command (ie better than standard mail with cron output)
  [ -s "$YUMTMP" ] && mail -s "System update: $SYSTEMNAME" $MAILTO < $YUMTMP
else
# default behavior is to use cron's internal mailing of output from cron-script
  cat $YUMTMP
fi
rm -f $YUMTMP

exit 0

 

yeah but no way to set email notifications by default as no idea of end users email address

 

yeah then it wouldn't be unattended.. but yeah plan to add EMAIL option to centmin.sh so can use variable for stuff like this

 

That's the plan

 

yeah one per day and only notify if there is an update. You can check your cron log at /var/log/cron to see if it ran

Code:

grep yum.cron /var/log/cron | tail -10
Sep 29 03:24:01 vultr run-parts(/etc/cron.daily)[21165]: starting 0yum.cron
Sep 29 03:28:39 vultr run-parts(/etc/cron.daily)[21235]: finished 0yum.cron
Sep 30 04:45:01 vultr run-parts(/etc/cron.daily)[26324]: starting 0yum.cron
Sep 30 04:54:00 vultr run-parts(/etc/cron.daily)[26403]: finished 0yum.cron
Oct  1 03:39:01 vultr run-parts(/etc/cron.daily)[31068]: starting 0yum.cron
Oct  1 04:29:19 vultr run-parts(/etc/cron.daily)[31314]: finished 0yum.cron

and check yum log when it does notify of updates

Code:

tail -10 /var/log/yum.log 
Sep 27 04:08:45 Updated: nss-util-3.16.1-2.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-softokn-freebl-3.14.3-12.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-softokn-3.14.3-12.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-sysinit-3.16.1-7.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-3.16.1-7.el6_5.x86_64
Sep 27 04:08:45 Updated: nss-tools-3.16.1-7.el6_5.x86_64
Oct 01 04:29:18 Updated: 1:net-snmp-libs-5.5-49.el6_5.4.x86_64
Oct 01 04:29:18 Updated: 1:net-snmp-5.5-49.el6_5.4.x86_64
Oct 01 04:29:18 Updated: 1:net-snmp-utils-5.5-49.el6_5.4.x86_64
Oct 01 04:29:18 Updated: 1:net-snmp-devel-5.5-49.el6_5.4.x86_64

 

what about

Code:

grep yum.cron /var/log/cron 

could just be the cron log was rotated and a fresh empty log is now in place
you can check

Code:

ls -lahrt /var/log | grep cron