How to manage hosts

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Overview

Hosts are used to define a physical server, workstation, device, etc. that resides on your network. Services are the logical entities that hosts provide. A host definition stores its Name, Alias, and an IP Address along with a required Host Template definition and optional host object directives. The bulleted items below describe the various host components.

• Host Templates - ?(Required) Stores common object properties that are used to define multiple hosts. Templates are used to reduce the number of repetitive entries when defining objects. For example, when defining a new host you would first create a host template with common properties. Then, to define a specific host, you apply the properties using a host template. GroundWork Monitor does provide a generic-host template.
• Host and Service Profiles - Aid in the design and management of hosts and services. Service profiles are made up of multiple service definitions, and host profiles can incorporate service profiles.
• Parents - Are typically routers, switches, firewalls, etc. that lie between the monitoring host and a remote host. One or more parents can be assigned to a host definition.
• Host Groups - An arbitrary collection of hosts into named sets. The usage of host groups simplifies access control, drawing layering, status displays, notifications, scheduling maintenance, multi-server commands, and reports. One or more host groups can be assigned to a host definition.
• Extended Host Info - Entries are basically used to make the output from the status, statusmap, statuswrl, and extinfo CGIs look good.
• 2d and 3d Status Coordinates - Are optional and define the host's position in the Nagios 2d status map. 3d status coords are optional and define the host's positions in the Nagios 3d status map.
• Host and Service Escalation Trees - Are used to escalate contact notifications for a particular service, host, or host group.
• Services - These are predefined service definitions included in hosts individually or through service and host profiles.

Steps

Let's first define a new host template, and then use the New Host Wizard to create a new host using a template.

Defining a host template

1. Select Configuration > Hosts, Host Templates, and New.
2. In the Host Template Properties screen, enter a Name for the new host template. Continue by entering a check for selected template properties. By selecting the ? question mark next to each field you can view a description of the directive which also indicates if it is required or optional. Host templates also enable you to define and manage optional custom object variables.
3. When finished defining template properties and any custom object variables, select Save. Now that we have a new host template, you can use the New Host Wizard feature to create a new host using this template.
   
   Figure: Host Template
   

Creating a host using the New Host Wizard

Defining a new host

When creating a new host there are many objects that can be configured into a host definition. However after providing a Name, Alias, and IP Address, a Host Template is the only required object, all others are optional. Below, each of the five host property screens are described in detail.

1. Select Configuration > Hosts, and Host wizard which will display the first screen, Host Vitals.
2. In this screen, enter a Name for the new host, an Alias as a name to identify the host, and an IP address for the new host. The Host Profile option applies a set of pre-defined services to a host. We will cover Host Profiles in another section. Optionally enter Notes. This field is intended to hold a free-text description of this item. It is displayed in the Status application, and can be included in notifications via the $HOSTNOTES$ macro. It is commonly used to provide additional information about the item such as the team in charge of maintenance, the asset tag, or other identifying data. And, optionally select a Host Profile which can be used to aid the design and management of hosts.
3. Select Next which will display the Host Properties 1 screen.
   
   Figure: Defining a new host
   
   
4. In the Host Properties 1 screen we can select our previously defined Host Template, which will apply all of the directive settings from the template to our new host. Parents are typically routers, switches, firewalls, etc. that lie between the monitoring host and a remote host. A host can be assigned to one or more parent hosts. We will visit the Parents option in another section. Select Next to go to the Host Properties 2 screen.
   
   Figure: Host Properties 1
   
   
5. Host Groups are an arbitrary collection of hosts into named sets. The usage of host groups simplifies access control, drawing layering, status displays, notifications, scheduling maintenance, multi-server commands, and reports. Here you can add host groups for this host, in other words this host will be a member within the selected host groups. You will get a warning message during a Pre Flight Test or Commit if a host is not a member of any host group. Select and add a host group for this host. Select Next to go to the Select Services screen.
   
   Figure: Host Properties 2
   
6. At this point there are no services selected for our example Host Printer_Scanner_Fax. If we had selected a profile from the first screen you would see associated services listed. However, you can still select a profile or select individual services to apply to this host. Let's select the profile snmp-network, and click Add Profile. A list of all services will be displayed that are now associated with the new host. Here you can also modify and discard any services. Additionally, you can add individual services from the list. Select Next to go to the last screen.
   
   You can select Save as Profile to save the new host as a profile that can be used in the creation of other hosts, or just select Continue. At this point you may want to go ahead and create a few more new hosts. If you need to change any of the definitions, from the Configuration page select Hosts>Hosts>HostGroup>HostName>Detail. You will be in the Manage Host screen.
   
   Figure: Host Properties 3
   

Deleting multiple hosts

There is an easy way to delete one, many, or all hosts. The Delete Hosts tool completely removes the host, it's associated services, and any reference such a a membership in host groups, service groups, groups, and profiles.

1. Select Hosts from the Configuration page.
2. Select Delete hosts.
3. Next, in the Delete Hosts screen, select from the list of abbreviated host names and host addresses. For example, selecting "" lists all hosts, and 1* will list all hosts with an IP address that starts with the number 1. Example: If you used Discover to import hosts and learned that you imported a number of hosts beginning with "lab", you can select "lab" to list the specific hosts to be removed.
4. Once a host abbreviation is chosen the available hosts will be displayed. Select the check box next to each host to be removed.
5. Select Delete. Choose Check All and Delete to remove all hosts.

   If you select "*" to list all hosts and you select Check All to remove all hosts, the system will consider this action as an invalid configuration with no hosts and services. This should be avoided.

   You will need to select Control>Commit, to complete the task of removing a host.

   Also, you can use the Configuration option Hosts in the Detail screen to accomplish the same task one host at a time.

   Figure: Delete multiple hosts