Sempre quando estamos configurando o Nagios, podemos esquecer ou apenas digitar uma informação errada nos arquivos de configuração. E quando vamos iniciá-lo pela primeira vez ou reiniciá-lo, somos surpreendidos com uma mensagem de ERROR.

Em pesquisas encontrei um item interessante que verifica as configurações do Nagios e mostra onde está o erro. Em anexo seguem algumas imagens que capturei para melhor ilustrar as informações a seguir.

O comando funciona da seguinte forma:

No CentOS:

# /usr/bin/nagios -v /etc/nagios/nagios.cfg

No Ubuntu:

sudo /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

O parâmetro -v faz a verificação dos arquivos de configuração do Nagios e mostra onde está o erro. Com isso vamos diminuir e muito o tempo de configuração dos nossos hosts/serviços. Para ver mais opções que podem ser usadas basta usar o /usr/bin/nagios --help. Logo abaixo segue um exemplo de saída do comando; # /usr/bin/nagios -v /etc/nagios/nagios.cfg

Nagios Core 3.2.3
Copyright (c) 2009-2010 Nagios Core Development Team and Community Contributors
Copyright (c) 1999-2009 Ethan Galstad
Last Modified: 10-03-2010
License: GPL

Website: http://www.nagios.org
Reading configuration data...
   Read main config file okay...
Processing object config file '/etc/nagios/objects/commands.cfg'...
Processing object config file '/etc/nagios/objects/contacts.cfg'...
Processing object config file '/etc/nagios/objects/timeperiods.cfg'...
Processing object config file '/etc/nagios/objects/templates.cfg'...
Processing object config directory '/etc/nagios/objects/dir_conf'...
Processing object config file '/etc/nagios/objects/dir_conf/box_services.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/services_firewall.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/hosts_mail.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/services_mail.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/hosts_firewall.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/wg_services.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/links_services.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/grupos.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/links_hosts.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/box_hosts.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/wg_hosts.cfg'...
Error: Could not find any host matching 'wg_vecto' (config file '/etc/nagios/objects/dir_conf/wg_services.cfg', starting on line 2)
Error: Could not expand hostgroups and/or hosts specified in service (config file '/etc/nagios/objects/dir_conf/wg_services.cfg', starting on
line 2)
   Error processing object config files!


***> One or more problems was encountered while processing the config files...

     Check your configuration file(s) to ensure that they contain valid
     directives and data defintions.  If you are upgrading from a previous
     version of Nagios, you should be aware that some variables/definitions
     may have been removed or modified in this version.  Make sure to read
     the HTML documentation regarding the config files, as well as the
     'Whats New' section to find out what has changed.

Ele encontra o erro, indica o arquivo que o contém,e ainda fala o número da linha. No meu teste apenas tirei a letra "r" do nome do host. Quando as configurações estão corretas, ele mostra da seguinte forma:

# /usr/bin/nagios -v /etc/nagios/nagios.cfg

Nagios Core 3.2.3
Copyright (c) 2009-2010 Nagios Core Development Team and Community Contributors
Copyright (c) 1999-2009 Ethan Galstad
Last Modified: 10-03-2010
License: GPL

Website: http://www.nagios.org
Reading configuration data...
   Read main config file okay...
Processing object config file '/etc/nagios/objects/commands.cfg'...
Processing object config file '/etc/nagios/objects/contacts.cfg'...
Processing object config file '/etc/nagios/objects/timeperiods.cfg'...
Processing object config file '/etc/nagios/objects/templates.cfg'...
Processing object config directory '/etc/nagios/objects/dir_conf'...
Processing object config file '/etc/nagios/objects/dir_conf/box_services.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/services_firewall.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/hosts_mail.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/services_mail.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/hosts_firewall.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/wg_services.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/links_services.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/grupos.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/links_hosts.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/box_hosts.cfg'...
Processing object config file '/etc/nagios/objects/dir_conf/wg_hosts.cfg'...
   Read object config files okay...

Running pre-flight check on configuration data...

Checking services...
        Checked 185 services.
Checking hosts...
        Checked 55 hosts.
Checking host groups...
        Checked 5 host groups.
Checking service groups...
        Checked 0 service groups.
Checking contacts...
        Checked 4 contacts.
Checking contact groups...
        Checked 2 contact groups.
Checking service escalations...
        Checked 0 service escalations.
Checking service dependencies...
        Checked 0 service dependencies.
Checking host escalations...
        Checked 0 host escalations.
Checking host dependencies...
        Checked 0 host dependencies.
Checking commands...
        Checked 35 commands.
Checking time periods...
        Checked 7 time periods.
Checking for circular paths between hosts...
Checking for circular host and service dependencies...
Checking global event handlers...
Checking obsessive compulsive processor commands...
Checking misc settings...

Total Warnings: 0
Total Errors:   0

Things look okay - No serious problems were detected during the pre-flight check

Espero ajudar com essa dica, pois perdi muito tempo verificando várias vezes os meus arquivos em busca de erro. Já que a ferramenta nos dá essa opção, vamos usar.