Posts Tagged ‘directive’

Monitoring Windows hosts with Nagios on Debian GNU/Linux

Tuesday, August 30th, 2011

Nagios logo install and configure nagios to monitor Windows hosts with on Debian GNU/Linux

In this article in short, I’ll explain how I configured Nagios on a Debian GNU/Linux release (Squeeze 6) to monitor a couple of Windows hosts running inside a local network. Now let’s start.

1. Install necessery nagios debian packages

apt-get install nagios-images nagios-nrpe-plugin nagios-nrpe-server nagios-plugins nagios-plugins-basic nagios-plugins-standard
nagios3 nagios3-cgi nagios3-common nagios3-core

2. Edit /etc/nagios-plugins/config/nt.cfg

In the File substitute:

define command { command_name check_nt command_line /usr/lib/nagios/plugins/check_nt -H '$HOSTADDRESS$' -v '$ARG1$' }

With:

define command {
command_name check_nt
command_line /usr/lib/nagios/plugins/check_nt -H '$HOSTADDRESS$' -p 12489 -v $ARG1$ $ARG2$
}

3. Modify nrpe.cfg to put in allowd hoss to connect to the Nagions nrpe server

vim /etc/nagios/nrpe.cfg

Lookup inside for nagios’s configuration directive:

allowed_hosts=127.0.0.1

In order to allow more hosts to report to the nagios nrpe daemon, change the value to let’s say:

allowed_hosts=127.0.0.1,192.168.1.4,192.168.1.5,192.168.1.6

This config allows the three IPs 192.168.1.4-6 to be able to report for nrpe.

For the changes to nrpe server to take effect, it has to be restrarted.

debian:~# /etc/init.d/nagios-nrpe-server restart

Further on some configurations needs to be properly done on the nrpe agent Windows hosts in this case 192.168.1.4,192.168.1.5,192.168.1.6

4. Install the nsclient++ on all Windows hosts which CPU, Disk, Temperature and services has to be monitored

Download the agent from http://sourceforge.net/projects/nscplus and launch the installer, click twice on it and follow the installation screens. Its necessery that during installation the agent has the NRPE protocol enabled. After the installation is complete one needs to modify the NSC.ini
By default many of nsclient++ tracking modules are not enabled in NSC.ini, thus its necessery that the following DLLs get activated in the conf:

FileLogger.dll
CheckSystem.dll
CheckDisk.dll
NSClientListener.dll
SysTray.dll
CheckEventLog.dll
CheckHelpers.dll

Another requirement is to instruct the nsclient++ angent to have access to the Linux installed nagios server again with adding it to the allowed_hosts config variable:

allowed_hosts=192.168.1.1

In my case the Nagios runs on Debian Lenny (Squeeze) 6 and possess the IP address of 192.168.1.1
To test the intalled windows nsclient++ agents are properly installed a simple telnet connection from the Linux host is enough:

5. Create necessery configuration for the nagios Linux server to include all the Windows hosts which will be monitored

There is a window.cfg template file located in /usr/share/doc/nagios3-common/examples/template-object/windows.cfg on Debian.

The file is a good start point for creating a conf file to be understand by nagios and used to periodically refresh information about the status of the Windows hosts.

Thus it’s a good idea to copy the file to nagios3 config directory:

debian:~# mkdir /etc/nagios3/objects
debian:~# cp -rpf /usr/share/doc/nagios3-common/examples/template-object/windows.cfg /etc/nagios3/objects/windows.cfg

A sample windows.cfg content, (which works for me fine) and monitor a couple of Windows nodes running MS-SQL service and IIS and makes sure the services are up and running are:

define host{
use windows-server ; Inherit default values from a template
host_name Windows1 ; The name we're giving to this host
alias Iready Server ; A longer name associated with the host
address 192.168.1.4 ; IP address of the host
}
define host{
use windows-server ; Inherit default values from a template
host_name Windows2 ; The name we're giving to this host
alias Iready Server ; A longer name associated with the host
address 192.168.1.4 ; IP address of the host
}
define hostgroup{
hostgroup_name windows-servers ; The name of the hostgroup
alias Windows Servers ; Long name of the group
}
define hostgroup{
hostgroup_name IIS
alias IIS Servers
members Windows1,Windows2
}
define hostgroup{
hostgroup_name MSSQL
alias MSSQL Servers
members Windows1,Windows2
}
define service{
use generic-service
host_name Windows1
service_description NSClient++ Version
check_command check_nt!CLIENTVERSION
}
define service{ use generic-service
host_name Windows1
service_description Uptime
check_command check_nt!UPTIME
}
define service{ use generic-service
host_name Windows1
service_description CPU Load
check_command check_nt!CPULOAD!-l 5,80,90
}
define service{
use generic-service
host_name Windows1
service_description Memory Usage
check_command check_nt!MEMUSE!-w 80 -c 90
define service{
use generic-service
host_name Windows1
service_description C: Drive Space
check_command check_nt!USEDDISKSPACE!-l c -w 80 -c 90
}
define service{
use generic-service
host_name Windows1
service_description W3SVC
check_command check_nt!SERVICESTATE!-d SHOWALL -l W3SVC
}
define service{
use generic-service
host_name Windows1
service_description Explorer
check_command check_nt!PROCSTATE!-d SHOWALL -l Explorer.exe
}
define service{
use generic-service
host_name Windows2
service_description NSClient++ Version
check_command check_nt!CLIENTVERSION
}
define service{ use generic-service
host_name Windows2
service_description Uptime
check_command check_nt!UPTIME
}
define service{ use generic-service
host_name Windows2
service_description CPU Load
check_command check_nt!CPULOAD!-l 5,80,90
}
define service{
use generic-service
host_name Windows2
service_description Memory Usage
check_command check_nt!MEMUSE!-w 80 -c 90
define service{
use generic-service
host_name Windows2
service_description C: Drive Space
check_command check_nt!USEDDISKSPACE!-l c -w 80 -c 90
}
define service{
use generic-service
host_name Windows2
service_description W3SVC
check_command check_nt!SERVICESTATE!-d SHOWALL -l W3SVC
}
define service{
use generic-service
host_name Windows2
service_description Explorer
check_command check_nt!PROCSTATE!-d SHOWALL -l Explorer.exe
}
define service{ use generic-service
host_name Windows1
service_description SQL port Check
check_command check_tcp!1433
}
define service{
use generic-service
host_name Windows2
service_description SQL port Check
check_command check_tcp!1433
}
The above config, can easily be extended for more hosts, or if necessery easily setup to track more services in nagios web frontend.
6. Test if connectivity to the nsclient++ agent port is available from the Linux server

debian:~# telnet 192.168.58.6 12489
Trying 192.168.58.6...
Connected to 192.168.58.6.
Escape character is '^]'.
asd
ERROR: Invalid password.

Another good idea is to launch on the Windows host the NSClient++ (system tray) , e.g.:

Start, All Programs, NSClient++, Start NSClient++ (system tray).

Test Nagios configuration from the Linux host running nagios and nrpe daemons to check if the check_nt, can succesfully authenticate and retrieve data generated from the nsclient++ on the Windows host:

debian:~# /usr/lib/nagios/plugins/check_nt -H 192.168.1.5 -p 12489 -v CPULOAD -w 80 -c 90 -l 5,80,90,10,80,90

If everything is okay and the remote Windows system 192.168.1.5 has properly configured and running NSClient++ the above command should return an output like:

CPU Load 1% (5 min average) 1% (10 min average) | '5 min avg Load'=1%;80;90;0;100 '10 min avg Load'=1%;80;90;0;100

In case of the command returns:

could not fetch information from server

instead this means that probably there is some kind of problem with authentication or handshake of the Linux host’s nagios check_nt to the Windows server’s running on 12489.

This is sometimes caused by misconfigured NSC.ini file, however in other occasions this error is caused by misconfigured Windows Firewall or because the NSClient++ is not running with Administrator user.

By the way important note to make about Windows 2008r2 is that if NSClient++ is running there it’s absolutely required to Login with Windows Administrator and run the NSClient++ /start , if it’s run through the Run As Adminsitrator with an admin privileged user the aforementioned error might appear, so be careful.
I’ve experienced this error myself and it took me about 40 minutes to find that I have to run it directly with Administrator user after logging as Administrator.

7. Create nagios web iface Apache configuration

nagios debian pachage is shipped with a config which is suitable to be setdebian:~# cp -rpf /usr/share/doc/nagios3-common/examples/apache2.conf /etc/apache2/sites-avalable/nagios
debian:~# ln -sf /etc/apache2/sites-available/nagios /etc/apache2/sites-enabled/nagios

The /etc/apache2/sites-available/nagios can easily be configured to work on Virtualhost, to do so the above copied file need to be wrapped inside a VirtualHost directive. For that put in the beginning of the file;

<VirtualHost *:80>

and in the end of the file:

<VirtualHost *:80>

8. Restart nagios server and Apache for the new settings to take effect

debian:~# /etc/init.d/apache2 restart
...
debian:~# /etc/init.d/nagios3 restart

If some custom configuration about tracking the Debian Linux nagios host running services needs to be made, its also helpful for one to check in /etc/nagios3/conf.d

Well that’s mostly what I had to do to make the Nagios3 server to keep track of a small Windows network on Debian GNU/Linux Squeeze 6, hope this small article helps. Cheers 😉

How to fix “Could not verify this certificate for unknown reasons” SSL certificate lighttpd troubles

Tuesday, June 28th, 2011

Firefox SSL Pro could not verify for uknown reasons solve error

I’ve been issuing new wildcard multiple SSL certificate to renew an expiring ones. After I completed the new certificate setup manually on the server (a CentOS 5.5 Final running SoluSVM Pro – Virtual Private Manager), I launched Firefox to give a try if the certificate is properly configured.

Instead of my expectations that the browser would just accept the certificate without spitting any error messages and all will be fine, insetad I got error with the just installed certificate and thus the browser failed to report the SSL cert is properly authenticated.

The company used to issue the SSL certificate is GlobeSSL – http://globessl.com , it was quite “hassle”, with the tech support as the first certficate generated by globessl was generation based on SSL key file with 4096 key encryption.

As the first issued Authenticated certificate generated by GlobeSSL was not good further on about a week time was necessery to completethe required certificate reissuing ….

It wasn’t just GlobeSSL’s failure, as there were some spam filters on my side that was preventing some of GlobeSSL emails to enter normally, however what was partially their fault as they haven’t made their notification and confirmation emails to pass by a mid-level strong anti-spam filter…

Anyways my overall experience with GlobeSSL certificate reissue and especially their technical support is terrible.
To make a parallel, issuing certificates with GoDaddy is a way more easier and straight forward.

Now let me come back to the main certificate error I got in Firefox …

A bit of further investigation with the cert failure, has led me to the error message which tracked back to the newly installed SSL certificate issues.
In order to find the exact cause of the SSL certificate failure in Firefox I followed to the menus:

Tools -> Page Info -> Security -> View Certificate

Doing so in the General browser tab, there was the following error:

Could not verify this certificate for unknown reasons

The information on Could not verify this certificate for unknown reasons on the internet was very mixed and many people online suggested many possible causes of the issue, so I was about to loose myself.

Everything with the certificate seemed to be configured just fine in lighttpd, all the GlobeSSL issued .cer and .key file as well as the ca bundle were configured to be read used in lighttpd in it’s configuration file:
/etc/lighttpd/lighttpd.conf

Here is a section taken from lighttpd.conf file which did the SSL certificate cert and key file configuration:

$SERVER["socket"] == "0.0.0.0:443" {
ssl.engine = "enable"
ssl.pemfile = "/etc/lighttpd/ssl/wildcard.mydomain.bundle"
}

The file /etc/lighttpd/ssl/wildcard.mydomain.bundle was containing the content of both the .key (generated on my server with openssl) and the .cer file (issued by GlobeSSL) as well as the CA bundle (by GlobeSSL).

Even though all seemed to be configured well the SSL error Could not verify this certificate for unknown reasons was still present in the browser.

GlobeSSL tech support suggested that I try their Web key matcher interfacehttps://confirm.globessl.com/key-matcher.html to verify that everything is fine with my certificate and the cert key. Thanks to this interface I figured out all seemed to be fine with the issued certificate itself and something else should be causing the SSL oddities.
I was further referred by GlobeSSL tech support for another web interface to debug errors with newly installed SSL certificates.
These interface is called Verify and Validate Installed SSL Certificate and is found here

Even though this SSL domain installation error report and debug tool did some helpful suggestions, it wasn’t it that helped me solve the issues.

What helped was First the suggestion made by one of the many tech support guy in GlobeSSL who suggested something is wrong with the CA Bundle and on a first place the documentation on SolusVM’s wiki – http://wiki.solusvm.com/index.php/Installing_an_SSL_Certificate .
Cccording to SolusVM’s documentation lighttpd.conf‘s file had to have one extra line pointing to a seperate file containing the issued CA bundle (which is a combined version of the issued SSL authority company SSL key and certificate).
The line I was missing in lighttpd.conf (described in dox), looked like so:

ssl.ca-file = “/usr/local/solusvm/ssl/gd_bundle.crt”

Thus to include the directive I changed my previous lighttpd.conf to look like so:

$SERVER["socket"] == "0.0.0.0:443" {
ssl.engine = "enable"
ssl.pemfile = "/etc/lighttpd/ssl/wildcard.mydomain.bundle"
ssl.ca-file = "/etc/lighttpd/ssl/server.bundle.crt"
}

Where server.bundle.crt contains an exact paste from the certificate (CA Bundle) mailed by GlobeSSL.

There was a couple of other ports on which an SSL was configured so I had to include these configuration directive everywhere in my conf I had anything related to SSL.

Finally to make the new settings take place I did a lighttpd server restart.

[root@centos ssl]# /etc/init.d/lighttpd restart
Stopping lighttpd: [ OK ]
Starting lighttpd: [ OK ]

After lighttpd reinitiated the error was gone! Cheers ! 😉

Few nginx.conf configuration options for Nginx to improve webserver performance

Tuesday, April 12th, 2011

Nginx server main logo with russian star
From my previous two articles How to install nginx webserver from source on Debian Linux / Install Latest Nginx on Debian and How to enable output compression (gzipfile content compression) in nginx webserver , I have explained how the Nginx server can be installed and configured easily.

As I’m continuing my nginx adventures this days, by trying to take the best out of the installed nginx server, I’ve found few configuration options, which does improve nginx’s server performance and thought it might be nice to share it here in hope that some other nginx novice might benefit out if them.
To setup and start using the options you will have of course to place the conf directives in /usr/local/nginx/conf/nginx.conf or wherever your nginx.conf is located.

The configuration options should be placed in nginx’s conf section which starts up with:

http {

Here are the configuration options useful in hastening my nginx’s performance:

1. General options nginx settings

## General Options
ignore_invalid_headers on;
keepalive_requests 2000;
recursive_error_pages on;
server_name_in_redirect off;
server_tokens off;

2. Connection timeout nginx settings

## Timeouts
client_body_timeout 60;
client_header_timeout 60;
keepalive_timeout 60 60;
send_timeout 60;
expires 24h;

3. server options for better nginx tcp/ip performance

## TCP options
tcp_nodelay on;
tcp_nopush on;

4. Increase the number of nginx worker processes

Somewhere near the beginning of nginx.conf file you should have the directive option:

worker_processes 1;

Make sure you change this option to:

worker_processes 4;

This will increase the number of spawned nginx worker processes in a way that more spawned threaded servers will await for client connections:

Being done with all the above settings, as a next step you have to restart the nginx server, in my case via the init script:

debian:~# /etc/init.d/nginx restart
Restarting nginx: nginx.

Now to check everything is fine with nginx and more specific that the worker_processes 4 options has taken place issue the command:

debian:~# ps axu |grep -i nginx|grep -v grep
root 20456 0.0 0.0 25280 816 ? Ss 10:35 0:00 nginx: master process /usr/local/nginx/sbin/nginx
nobody 20457 0.0 0.0 25844 1820 ? S 10:35 0:00 nginx: worker process
nobody 20458 0.0 0.0 25624 1376 ? S 10:35 0:00 nginx: worker process
nobody 20459 0.0 0.0 25624 1376 ? S 10:35 0:00 nginx: worker process
nobody 20460 0.0 0.0 25624 1368 ? S 10:35 0:00 nginx: worker process

Above you notice the 4 nginx processes running with user nobody, they’re the same configured worker_processes I just pointed out above.