Configuring remote service checks using nagios
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We can check lot of remote services including ping, http, ftp, smtp, pop3 and imap using nagios. For other services we can write our own check command, add command to commands.cfg file (located in /etc/nagios/objects in CentOS 5.4) and then check custom services.
Create configuration directory for hosts
For easier maintenance later it is better to put configuration of only one host in one configuration file. Also we can put all host configuration files in one directory, all switch configuration file in other directory and so on for easier management. Edit file 'nagios.cfg' and add/uncomment line like
cfg_dir=/etc/nagios/servers
After this create folder '/etc/nagios/servers' if it does not exists and change its user and group owner to nagios.
Configure host
To check services on a host we first define host and then we define services running on the host. To define host use
define host{
use linux-server ; Name of template
host_name students ; Short name of server, will be used in nagios configuration
alias students.iiit.ac.in ; Long name of server, will be used in reporting
address students.iiit.ac.in ; FQDN or IP address of host, will be used for checks
}
You have to add the above defination to file with extension .cfg and save the file in /etc/nagios/servers directory.
Add host to host group
Sample host groups are defined in sample configuration files. We can define our own host groups if we like. We can also add hosts to existing host groups. Sample host group 'Linux Servers' is defined in file 'localhost.cfg' and hence we can add more hosts to same group. Sample changed host group definition can be like
define hostgroup{
hostgroup_name linux-servers ; The name of the hostgroup
alias Linux Servers ; Long name of the group
members localhost,labpc,students,ss1 ; Comma separated list of hosts that belong to this group
}
Do not re-define hostgroup. Change the definition of hostgroup in localhost.cfg file whenever you want to add host to it
Configuring ping check
The simplest check is ping check. Modify host_name appropriately.
define service{
use generic-service ; Name of service template to use
host_name students
service_description PING
check_command check_ping!100.0,20%!500.0,60%
notifications_enabled 1
}
Check things are fine
After this check if things are fine using 'nagios -v' and then 'service nagios reload'. Open nagios web interface and see the host is being pinged properly. If all goes fine then you can add more services running on the host that can be accessed remotely
Checking SSH service
We can use something like this to configure check for SSH service. Modify host_name appropriately.
define service{
use generic-service ; Name of service template to use
host_name ss1
service_description SSH
check_command check_ssh
notifications_enabled 1
}
Checking HTTP service
define service{
use generic-service ; Name of service template to use
host_name ss1
service_description HTTP
check_command check_http
notifications_enabled 1
}
Checking FTP service
define service{
use generic-service ; Inherit default values from a template
host_name ss1
service_description FTP
check_command check_ftp
}
Checking SMTP service
define service{
use generic-service ; Inherit default values from a template
host_name students
service_description SMTP
check_command check_smtp
}
Checking IMAP service
define service{
use generic-service ; Inherit default values from a template
host_name students
service_description IMAP
check_command check_imap
}
Checking POP3 service
define service{
use generic-service ; Inherit default values from a template
host_name students
service_description POP3
check_command check_pop
}
Troubleshooting
Permission issues
If you see error 'It appears as though you do not have permission to view information for any of the services you requested...' then it is caused by username configuration in /etc/nagios/cgi.cfg where by default only nagiosadmin user has permissions to do everything. This is not desirable if LDAPAuthentication is being used for nagios. This can be solved by replacing nagiosadmin by a specific username or by * everywhere in /etc/nagios/cgi.cfg file.
Automated nagios configuration
For automated nagios configuration refer to:
Home > CentOS > CentOS 6.x > Monitoring tools > Nagios configuration > Configuring remote service checks using nagios
