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Server Monitoring With munin And monit On CentOS 5.2 - Page 2

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  1. 5 Install And Configure monit
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5 Install And Configure monit

Next we install monit:

yum install monit

Then we create the system startup links for monit:

chkconfig --levels 235 monit on

monit's default configuration file is /etc/monit.conf where you can find some configuration examples (you can find more configuration examples on http://mmonit.com/wiki/Monit/ConfigurationExamples) that are all commented out, but it tells monit to also look in the directory /etc/monit.d for configuration files, therefore instead of modifying /etc/monit.conf, we create a new configuration file /etc/monit.d/monitrc. In my case I want to monitor proftpd, sshd, mysql, apache, and postfix, I want to enable the monit web interface on port 2812, I want a https web interface, I want to log in to the web interface with the username admin and the password test, and I want monit to send email alerts to root@localhost, so my file looks like this:

vi /etc/monit.d/monitrc
set daemon  60
set logfile syslog facility log_daemon
set mailserver localhost
set mail-format { from: [email protected] }
set alert root@localhost
set httpd port 2812 and
     SSL ENABLE
     PEMFILE  /var/certs/monit.pem
     allow admin:test

check process proftpd with pidfile /var/run/proftpd.pid
   start program = "/etc/init.d/proftpd start"
   stop program  = "/etc/init.d/proftpd stop"
   if failed port 21 protocol ftp then restart
   if 5 restarts within 5 cycles then timeout

check process sshd with pidfile /var/run/sshd.pid
   start program  "/etc/init.d/sshd start"
   stop program  "/etc/init.d/sshd stop"
   if failed port 22 protocol ssh then restart
   if 5 restarts within 5 cycles then timeout

check process mysql with pidfile /var/run/mysqld/mysqld.pid
   group database
   start program = "/etc/init.d/mysqld start"
   stop program = "/etc/init.d/mysqld stop"
   if failed host 127.0.0.1 port 3306 then restart
   if 5 restarts within 5 cycles then timeout

check process apache with pidfile /var/run/httpd.pid
   group www
   start program = "/etc/init.d/httpd start"
   stop program  = "/etc/init.d/httpd stop"
   if failed host www.example.com port 80 protocol http
      and request "/monit/token" then restart
   if cpu is greater than 60% for 2 cycles then alert
   if cpu > 80% for 5 cycles then restart
   if totalmem > 500 MB for 5 cycles then restart
   if children > 250 then restart
   if loadavg(5min) greater than 10 for 8 cycles then stop
   if 3 restarts within 5 cycles then timeout

check process postfix with pidfile /var/spool/postfix/pid/master.pid
   group mail
   start program = "/etc/init.d/postfix start"
   stop  program = "/etc/init.d/postfix stop"
   if failed port 25 protocol smtp then restart
   if 5 restarts within 5 cycles then timeout

(Please make sure that you check processes only that really exist on your server - otherwise monit won't start. I.e., if you tell monit to check Postfix, but Postfix isn't installed on the system, monit won't start.)

The configuration file is pretty self-explaining; if you are unsure about an option, take a look at the monit documentation: http://mmonit.com/monit/documentation/monit.html

In the apache part of the monit configuration you find this:

   if failed host www.example.com port 80 protocol http
      and request "/monit/token" then restart

which means that monit tries to connect to www.example.com on port 80 and tries to access the file /monit/token which is /var/www/www.example.com/web/monit/token because our web site's document root is /var/www/www.example.com/web. If monit doesn't succeed it means Apache isn't running, and monit is going to restart it. Now we must create the file /var/www/www.example.com/web/monit/token and write some random string into it:

mkdir /var/www/www.example.com/web/monit
echo "hello" > /var/www/www.example.com/web/monit/token

Next we create the pem cert (/var/certs/monit.pem) we need for the SSL-encrypted monit web interface:

mkdir /var/certs
cd /var/certs

We need an OpenSSL configuration file to create our certificate. It can look like this:

vi /var/certs/monit.cnf
# create RSA certs - Server

RANDFILE = ./openssl.rnd

[ req ]
default_bits = 1024
encrypt_key = yes
distinguished_name = req_dn
x509_extensions = cert_type

[ req_dn ]
countryName = Country Name (2 letter code)
countryName_default = MO

stateOrProvinceName             = State or Province Name (full name)
stateOrProvinceName_default     = Monitoria

localityName                    = Locality Name (eg, city)
localityName_default            = Monittown

organizationName                = Organization Name (eg, company)
organizationName_default        = Monit Inc.

organizationalUnitName          = Organizational Unit Name (eg, section)
organizationalUnitName_default  = Dept. of Monitoring Technologies

commonName                      = Common Name (FQDN of your server)
commonName_default              = server.monit.mo

emailAddress                    = Email Address
emailAddress_default            = [email protected]

[ cert_type ]
nsCertType = server

Now we create the certificate like this:

openssl req -new -x509 -days 365 -nodes -config ./monit.cnf -out /var/certs/monit.pem -keyout /var/certs/monit.pem
openssl gendh 512 >> /var/certs/monit.pem
openssl x509 -subject -dates -fingerprint -noout -in /var/certs/monit.pem
chmod 700 /var/certs/monit.pem

Finally, we can start monit:

/etc/init.d/monit start

Now point your browser to https://www.example.com:2812/ (make sure port 2812 isn't blocked by your firewall), log in with admin and test, and you should see the monit web interface. It should look like this:

(Main Screen)

(Apache Status Page)

Depending on your configuration in /etc/monit.d/monitrc monit will restart your services if they fail and send notification emails if process IDs of services change, etc.

Have fun!

 

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