Nagios allows putting one or more comments associated with a host or a service. These can be anything from Third machine from the top on the left shelf to Reset button not working. Nagios also adds comments automatically in several cases, for example, when an object is scheduled for downtime a comment about it is placed.

Comments associated with a specific object are shown on the host and service detail information pages. They can also be added and removed from these pages.

Nagios also offers a page that allows managing comments for all hosts and services, similar to managing scheduled downtimes. It allows adding and deleting comments for all hosts. You can also navigate to the host or service detailed information page by clicking on an object name. The page can be accessed via the Comments link from the menu on the left.

The following is a screenshot of the comments page:

Clicking on the trash icon next to any comment will delete it. Adding a comment can be done by clicking on a host or service name and then doing so from the detailed information page or by clicking above the table with comments. In the latter case, you will need to specify the host name and service description in the add comment form.