Processes

Monit

Monit is a process monitor (and much more) that automatically restarts services when they are down. Sadly the version included in EPEL repository is quite old and doesn't support all the directives we want to use. We are going to install it through yum anyway, so we get the configuration and init scripts shiped with it:

yum install monit

To fetch the newest version directly from the developer's website, proceed with these steps:

cd /usr/local/src
wget http://mmonit.com/monit/dist/binary/5.8.1/monit-5.8.1-linux-x64.tar.gz
tar -xzvf monit-5.8.1-linux-x64.tar.gz

and move it to our location for non-distribution packages:

mv /usr/local/src/monit-5.8.1 /usr/local/pkgs

Consulting the Appendix, we can use graft to link it into our $PATH. Before we do that, we create a .graft-exclude file that instructs graft, which files and directories we want to symlink:

nano /usr/local/pkgs/monit-5.8.1/.graft-exclude

CHANGES
COPYING
conf

followed by issuing:

cd /usr/local/pkgs
graft -i -P monit-5.8.1

The last three steps include changing the default configuration file as well as fixing the init script to use our custom monit binary.

First, change some of the default configuration options:

nano /etc/monit.conf

set daemon  30              # check services at 30 sec intervals
    with start delay 30     # optional: delay the first check by another 30 sec (by
                            # default Monit check immediately after Monit start)

set mailserver localhost    # primary mailserver

set alert root@localhost    # receive all alerts

set httpd port 2812 and
    use address localhost  # only accept connection from localhost
    allow localhost        # allow localhost to connect to the server and

A set of configuration files for various services can be found in the Appendix.

Secondly, fix the init script:

nano /etc/init.d/monit

#!/bin/bash
#
# Init file for Monit system monitor
# Written by Stewart Adam <[email protected]>
# based on script by Dag Wieers <[email protected]>.
#
# chkconfig: - 98 02
# description: Utility for monitoring services on a Unix system
#
# processname: monit
# config: /etc/monit.conf
# pidfile: /var/run/monit.pid
# Short-Description: Monit is a system monitor

# Source function library.
. /etc/init.d/functions

### Default variables
CONFIG="/etc/monit.conf"
pidfile="/var/run/monit.pid"
prog="monit"
binary="/usr/local/bin/$prog"

# Check if requirements are met
[ -x "$binary" ] || exit 1
[ -r "$CONFIG" ] || exit 1

RETVAL=0

start() {
    echo -n $"Starting $prog: "
    daemon $binary -c $CONFIG
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && touch /var/lock/subsys/$prog
    return $RETVAL
}

stop() {
    echo -n $"Shutting down $prog: "
    killproc -p ${pidfile}
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/$prog
    return $RETVAL
}

restart() {
    stop
    start
}

reload() {
    echo -n $"Reloading $prog: "
    $binary -c "$CONFIG" reload
    RETVAL=$?
    echo
    return $RETVAL
}

case "$1" in
  start)
    start
    ;;
  stop)
    stop
    ;;
  restart)
    restart
    ;;
  reload)
    reload
    ;;
  condrestart)
    [ -e /var/lock/subsys/$prog ] && restart
    RETVAL=$?
    ;;
  status)
    status $prog
    RETVAL=$?
    ;;
  *)
    echo $"Usage: $0 {start|stop|restart|reload|condrestart|status}"
    RETVAL=1
esac

exit $RETVAL

And lastly, create an alias around the monit binary so one does not have to specify the system configuration file every time:

nano ~/.bash_aliases

alias monit='monit -c /etc/monit.conf'

Please note that installing through yum is not required - and only done to steal the configuration file, logrotate settings etc. If you prefer doing everything by hand, feel free to do so.