Monit is a open source utility for managing and monitoring, processes, files, directories and devices on a Unix system. Monit can perform automatic maintenance and repair and can execute useful actions in error situations.
E.g.
monit can start a process if it does not run,
monit can restart a process if it does not respond,
monit can stop a process if it uses to much resources.
You may use monit to monitor files, directories and devices for changes, such as timestamp changes, checksum changes or size changes.
Steps
1. Download the latest monit from rpmforge repository.
For x86 (32-bit) systems
http://apt.sw.be/redhat/el5/en/i386/rpmforge/RPMS/monit-5.2.5-1.el5.rf.i386.rpm
For x64 (64-bit) systems
http://apt.sw.be/redhat/el5/en/x86_64/rpmforge/RPMS/monit-5.2.5-1.el5.rf.x86_64.rpm
[root@server ~]# wget http://apt.sw.be/redhat/el5/en/i386/rpmforge/RPMS/monit-5.2.5-1.el5.rf.i386.rpm --2011-08-14 00:12:58-- http://apt.sw.be/redhat/el5/en/i386/rpmforge/RPMS/monit-5.2.5-1.el5.rf.i386.rpm Resolving apt.sw.be... 193.1.193.67 Connecting to apt.sw.be|193.1.193.67|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 573934 (560K) [application/x-redhat-package-manager] Saving to: `monit-5.2.5-1.el5.rf.i386.rpm' 100%[=============================================================>] 573,934 20.9K/s in 34s 2011-08-14 00:13:38 (16.6 KB/s) - `monit-5.2.5-1.el5.rf.i386.rpm' saved [573934/573934]
2. Install the monit rpm
[root@server ~]# rpm -Uvh monit-5.2.5-1.el5.rf.i386.rpm Preparing... ########################################### [100%] 1:monit ########################################### [100%]
3. Configure monit
[root@server ~]# vi /etc/monit.conf
set daemon 120 # check services at 2-minute intervals
set logfile syslog facility log_daemon
set mailserver mail.server.local, # primary mailserver
set alert admin@server.local
set httpd port 2812 and
allow localhost # allow localhost to connect to the server and
allow 192.168.2.2 # allow client ip address to connect to the server and
allow admin:monit # require user 'admin' with password 'monit'
4. Create /var/monit directory to place id and state
[root@server ~]# mkdir /var/monit
5. Configure service to be monitor
[root@server ~]# vi /etc/monit.d/localhost
check process httpd with pidfile /var/run/httpd.pid
start program = "/etc/init.d/httpd start"
stop program = "/etc/init.d/httpd stop"
if failed host 127.0.0.1 port 80 protocol http 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 host 127.0.0.1 port 22 protocol ssh then restart
if 5 restarts within 5 cycles then timeout
check process mysqld with pidfile /var/run/mysqld/mysqld.pid
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
6. Set monit to auto start on boot up.
[root@server ~]# vi /etc/default/monit # You must set this variable to for monit to start startup=1
or
[root@server ~]# chkconfig monit on
7. Start monit service
[root@server ~]# service monit start
Starting monit: monit: generated unique Monit id 50baacc26c17a307fe4cbdc1616c0bf8 and stored to '/var/monit/id'
Starting monit daemon with http interface at [*:2812]
[ OK ]
or
[root@server ~]# /etc/init.d/monit start
Starting monit: Starting monit daemon with http interface at [*:2812]
[ OK ]
8. Monitor monit from your browser
Monit Web interface will run on the port number 2812. Now point your browser to http://serverip:2812/