PRTG Manual: Setting Up Notifications Based on Sensor Limits: Example

Note: This documentation refers to the PRTG System Administrator user accessing the Ajax interface on a master node. For other user accounts, interfaces, or nodes, not all of the options might be available as described. When using a cluster installation, failover nodes are read-only by default.

This section will show you exemplarily how to set up a notification for exceeded disk free limits. The approach for this specific use case is examined step by step. You can easily adapt it to declare limits for other sensor types.

There are several steps to take in order to set up notifications based on limits:

  • Step 1: Provide necessary information about the delivery of notifications (SMTP and SMS).
  • Step 2: Create notifications, specifying the type of notification and its content.
  • Step 3: Define thresholds that will change a sensor's status (this is not necessary for every kind of notification).
  • Step 4: Add suitable triggers to objects which will evoke notifications if something is going wrong in your network.
  • Step 5: Test if the created notification will be triggered and delivered correctly.

Note: When you set up your own notifications, you will not necessarily need to go through all the steps described here. In this section, our main goal is to give you a general idea of the notifications concept.

Step 1: Setting up the Notification Delivery

Before creating notifications, you first have to define how those notifications actually will be delivered to your email account, mobile phone, or pager. To do so, choose Setup | System Administration | Notification Delivery from PRTG's main menu bar. Specify the mechanism of SMTP delivery, sender email and name, as well as the HELO ident. For SMS delivery, select your service provider and provide the corresponding credentials. You can find details about notification delivery in section System Administration—Notification Delivery.

Step 2: Setting up the Notification's Content

In order to get an informative message when a disk is running out of capacity, create a corresponding notification. Choose Setup | Account Settings | Notifications from PRTG's main menu bar and click on the button Add New Notification. Give the notification an explanatory name; in our case you could use Disk Free Limit Notification. However, if you want to trigger this notification on a global level (for example, for a probe or group) such that it would not only apply to breached disk free limits, a general name would be more suitable (like the predefined notification "Email to Admin"). If you leave the default text of the newly created notification, it will already contain all necessary information, like:

  • which sensor is affected,
  • since when the sensor is affected,
  • last value of this sensor,
  • etc.

See section More for the other options you have here.

After providing this basic information, select the delivery method. In our case, we choose Send Email for this notification by marking the corresponding checkbox. Specify who will receive the notification, its subject, the format, the content of the email, and its priority. By default, the email notification will contain several information parameters about the evoking sensor: its name, status, time, message, location in the device tree, etc. Feel free to adjust email messages to your needs (see section More). You can choose any other notification method, of course (see Account Settings—Notifications).

Creating an Email Notification

Creating an Email Notification

Once the notification is set up completely, click on Save. You will be redirected to the notifications overview page. You can now use this notification for every trigger on every object in your device tree.

Step 3: Define Limits

Before creating triggers that evoke notifications, first specify the limits which you want to apply to your disks. For example, if you want to be notified when a disk has exceeded 80% of its capacity, force the sensor into a Warning status at this utilization. You have several options to set limits for disk free sensors:

Step 3.1: Define Limits in Sensor Settings (Multi-Disk Free Sensors Only)

You can set limits for sensors monitoring multiple disks directly via the Settings tab on a sensor's details page. Multi-Edit for existing sensors is also possible. Open the settings of the selected sensor(s) and go to section Set limits checked against ALL disks. There, for example, enable Percentage Limit Check. In the field Lower Warning Limit, enter the percentage suitable to your needs. In our example, this would be 20. Alternatively, you can use bytes to define a limit. However, we recommend using percentage values for more flexibility. This limit will apply to all channels of this sensor representing disks.

Setting Limits for All Disks

Setting Limits for All Disks

Note: This sensor setting is only available for multi-drive sensors. You can omit Step 3.1 for all sensors that are not from the type "disk free".

Step 3.2: Define Limits for Sensor Channels

In order to set specific limits for single disks, use the sensor's Channel settings. You can open channel settings via the gear icon in the respective channel gauge or in the channels table. Enable Limits at the bottom of the channel settings dialog and specify your desired limits in the Lower Warning Limit field. This limit will only apply to the respective channel.

Note: If you define channel limits when using the sensor's limit setting in the sensor's Settings tab at the same time, the first limit that applies will be considered. This way, you can individually define harder limits for single disks in a multi-disk sensor. All defined limits are valid side-by-side.

You have to take the approach via channel settings for sensor types that monitor only one (logical) disk, for example, the SNMP Disk Free Sensor. For these sensor types, you can use Multi-Edit if you want to apply the same limits for each of these sensors automatically.

  • To see all sensors of this type at a glance, just filter for it: From PRTG's main menu bar, choose Sensors | By Type | SNMP Disk Free.
  • Mark the checkboxes of the sensors you want to add a limit for.
  • Click the screwdriver symbol in the multi-edit bar.
  • Open the Channel Settings tab.
  • Select the channel you want to add a limit for; in this case it would be most likely the channel Free Space.
  • Then Enable Limits at the bottom of the dialog and enter the number in the correct field as described above.

Once done, save these settings—the new limit will apply to all channels with this name of the multi-edited sensors.

Setting Limits for Channels with Multi-Edit

Setting Limits for Channels with Multi-Edit

Step 4: Setting up the Notification Trigger

You have specified limits to define when a sensor will go into a Warning (or Error) status. Now you can create the according triggers. The trigger we use in this example is the State Trigger. For details about other possible notification triggers, see section More.

  • You can set up a State Trigger on any level in your device tree. For example, open a group containing the device(s) representing your disks.
  • Go on the Notifications tab.
  • Click Add State Trigger.
  • Set the trigger to "When sensor is Warning" and choose the notification you have created before ("Disk Free Limit Notification" or a more general one) from the drop down list.
  • Adjust the other notification settings to your needs and save this new object trigger.

Now you will be notified immediately when the capacity of one of your disks falls below the defined limit, in this case 20% free disk space.

Setting a Trigger for Disk Free Limit Notification

Setting a Trigger for Disk Free Limit Notification

Step 5: Testing the Notification

Finally, test the notification which you have created. You can trigger this notification for test purposes immediately:

  • From the main menu bar, choose Setup | Account Settings | Notifications.
  • For the respective notification, click on the corresponding Test button.

Then, check if the notification was triggered and delivered correctly, depending on what delivery method you defined before. If you do not get a notification (or a defined action is not executed) at all, check the notification logs: From the main menu bar, choose Logs | System Events | Notifications. Look for the triggered notification in the table list (verifying that the notification delivery is set up correctly in general) and consider the corresponding message. See section Logs for more information.


This section provides information about additional options you have when working with notifications.

  • Notification Settings:
    You can create schedules to activate notifications only at specific times, for example, only on weekdays. In section Notification Summarization you can choose between various options to avoid message floodings. Furthermore, define which user groups will have access to edit this notification. For details about notification settings, refer to section Account Settings—Notifications.
  • Other Triggers:
    An alternative to the state trigger would be to add a Threshold Trigger; then you would not need to set up limits explicitly, though, this trigger type would only be suitable for disk free sensors when using the trigger for single sensors, one by one. Free disk sensors have free space in percent as primary by default, other sensors have primary channels with the units bytes or seconds. However, threshold triggers only apply to the primary or total channel. General notification triggering by threshold might not work as expected for sensors of the "percentage" type. You can find all available triggers in section Notifications.
  • Add a Threshold Trigger to a sensor directly:
    Go on a sensor's detail page and select the Notifications tab. Click on Add Threshold Trigger, select the desired channel, and provide the condition when this notification will be sent. In this example for free disk space, the setting would be "When Free Bytes C: (%) channel is Below 20 for at least 60 seconds perform Disk Free Limit Notification".
  • Notifications with Libraries:
    If your disk devices are spread over many groups, we recommend you to use a PRTG library for your disks. Choose Libraries | All diskspace sensors from the main menu bar, go on the Notifications tab, and add a state trigger as described above. Note: Not all disk free sensor types might appear. You can add them to this library in the settings of the library node. There you can filter by type or tag and add missing sensors this way. You can also filter by priority and other sensor properties.
Settings of a Library with Diskspace Sensors

Settings of a Library with Diskspace Sensors



Ajax Web Interface—Advanced Procedures—Topics


Other Ajax Web Interface Sections


Related Topics