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Month: November 2015

URL Monitoring With Nagios


Nagios provides complete URL monitoring of HTTP and HTTPS servers and protocols as well as full URL transaction monitoring.


Implementing effective URL monitoring with Nagios offers the following benefits:
* Increased server, services, and application availability
* Fast detection of network outages and protocol failures
* Monitor user experience when accessing URLs
* Web server performance monitoring
* Web transaction monitoring
* URL monitoring

URL monitoring

By using the ‘check_http’ nagios command, we can monitor a specific url rather than checking the Apache service is up or not. This method is helpful to identify if the website is hacked and url is injected with malicious codes or there is some Apache or php errors and page is throwing an error instead. The normal Apache service check will return successful results in the above case.
We can check for a specific keyword string on the webpage. If that string not present, an error will be returned.

Here is an real example

define service{
    use                            urlmonitoring-service
    service_description            url_check
    check_command                  check_http!-H -t 30 -R "Cpanel and WHM" -f follow

The above will check for the keyword “Cpanel and WHM” on the page “”. If the keyword is missing or the page is not responding nagios will retun and error.

URL monitoring +SSL

You can refer to below example if the web page has SSL/TLS enabled.

define service{
    use                            urlmonitoring-service
    service_description            url_check
    check_command                  check_http!-H -t 30 -R "Cpanel and WHM" -f follow --ssl

Here we added the option “–ssl” to the check command

URL monitoring on ht password protected page

Normal method will not work as we need to validate ht password protection first to see the page. You can use the following example for such pages.

define service{
    use                            urlmonitoring-service
    service_description            url_check_protected
    check_command                  check_http!-H -a user:password -t 30 -R "Cpanel and WHM" -f follow --ssl 

Replace the username and password appropriately.

Run Postfix on multiple ports

Adding additional SMTP listenerports

By default postfix run on port 25 and 587(TLS). However some ISPs block port 25. In that case you can configure the postfix mail server to listen on addional ports too, for example port 26 or some random 5125.

This configuration is done in the configuration file. Edit it in your editor of choice.

This file is in the following format:

# ==========================================================================
# service type private unpriv chroot wakeup maxproc command + args
# (yes) (yes) (yes) (never) (100)
# ==========================================================================

The first column is the port number that you want to listen on. The default SMTP port 25 line will read as follows:

smtp inet n - - - - smtpd

To add an additional listener port of 5125, insert the the following after the above:

5125 inet n - n - - smtpd

Save the file and restart postfix service

service postfix restart

Now you can use port 25, 587 and 5125 to connect to your mail server.

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