PRTG Manual: SSH Script Sensor

Sensor Settings

Script

Select a script file from the list. The dropdown menu will list all script files available in the /var/prtg/scripts directory on the target Linux/Unix system. For a script file to appear in this list, store the target file into this directory. Ensure the script has executable rights.

To show the expected sensor value and status, your file must use the correct format for the returned values. In this case it is exitcode:value:message to standard output stdout. The exit code determines the sensor status.

For detailed information on the expected return format and on how to build custom sensors, please see the PRTG API documentation (Application Programming Interface (API) Definition). There you will find detailed information on the Custom Sensors tab. For an example script, please see More section below.

Value Type

Define the type of the values that your script returns. Choose between:

• Integer: The return values are from the type integer. If the script returns a float, PRTG will show the value 0.

• Float: The return values are from the type float, with a dot (.) between pre-decimal position and decimal places. In this setting, the sensor will also display integer values unless they produce a buffer overflow.

• Counter: Your script returns varying integer values. PRTG will show the difference between the values of two sensor scans.
  A counter must return an integer, float values are not supported.
   

This sensor type does not support string values.

Channel Name

Enter a name for the channel in which the sensor shows returned values. Please enter a string. This is for display purposes only. You can change the name later in the sensor's channel settings.

Sensor Name

Enter a meaningful name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.

Parent Tags

Shows Tags that this sensor inherits from its parent device, group, and probe. This setting is shown for your information only and cannot be changed here.

Tags

Enter one or more Tags, separated by spaces or commas. You can use tags to group sensors and use tag–filtered views later on. Tags are not case sensitive. We recommend that you use the default value.

You can add additional tags to the sensor if you like. Other tags are automatically inherited from objects further up in the device tree. These are visible above as Parent Tags.

Priority

Select a priority for the sensor. This setting determines where the sensor is placed in sensor lists. Top priority is at the top of a list. Choose from one star (low priority) to five stars (top priority).

Script

Shows the name of the script that the sensor executes with each scan. Once a sensor is created, you cannot change this value. It is shown for reference purposes only. If you need to change this, please add the sensor anew.

Character Encoding

Define the character encoding you use in your script to correctly display the sensor message. Choose between:

• UTF-8 (default)
• ASCII

Parameters

If your script file catches command line parameters, you can define them here. You can use placeholders as well. For a full list of all placeholders please see the API documentation (Application Programming Interface (API) Definition).

Note: Please make sure you write the placeholders in quotes to ensure that they are working properly if their values contain blanks. Use single quotation marks ' ' with PowerShell scripts, and double quotes " " with all others. In Secure Shell (SSH) scripts, you can use alphanumeric characters and the special characters ".", "_", "-", "=", and "/" outside of quoted strings.

Please enter a string or leave the field empty.

Mutex Name

Define any desired mutex name for the process. PRTG will run all custom script sensors having the same mutex name serially (not simultaneously). This is useful if you use a lot of sensors and want to avoid high resource usage caused by processes running at the same time. Please enter a string or leave the field empty.

For links to more information, please see the More section below.

Unit String

Define a unit for the channel value. Please enter a string. This is for display purposes only and will be the default unit for a new channel.  You can change the unit after sensor creation in the sensor's channel settings.

Value Type

Shows the expected type of the returned value. Once a sensor is created, you cannot change this value. It is shown for reference purposes only. If you need to change this, please add the sensor anew.

If Value Changes

Define what this sensor will do when the sensor value changes. You can choose between:

• Ignore changes (default): The sensor takes no action on change.
• Trigger 'change' notification: The sensor sends an internal message indicating that its value has changed. In combination with a Change Trigger, you can use this mechanism to trigger a notification whenever the sensor value changes.

Connection Timeout (Sec.)

Define a timeout in seconds for the connection. This is the time the sensor will wait to establish a connection to the host. Keep this value as low as possible. The maximum value is 900 seconds (15 minutes). Please enter an integer value.

Shell Timeout (Sec.)

Define a timeout in seconds for the shell response. This is the time in seconds the sensor will wait for the shell to return a response after it has sent its specific command (for example, cat /proc/loadavg). The maximum value is 300 seconds (5 minutes). Please enter an integer value.

SSH Port

Define which port this sensor uses for the SSH connection. Choose between:

• Inherit port number from parent device (default): Use the port number as defined in the Credentials for Linux/Solaris/Mac OS (SSH/WBEM) Systems section of the device this sensor is created on.
• Enter custom port number: Define a custom port number below and do not use the port number from the parent device settings.

Use Port Number

This field is only visible if you choose Enter custom port number above. Enter the port number (between 1 and 65535) that this sensor will use for the SSH connection. Please enter an integer value.

SSH Engine

Select the method you want to use to access data with this SSH sensor. We strongly recommend that you use the default engine! For some time you still can use the legacy mode to ensure compatibility with your target systems. Choose between:

• Inherit from parent device (default): Use the SSH engine that you have defined in the parent device settings or higher in the object hierarchy. If you did not change it, this is the recommended default engine.
• Default: This is the default monitoring method for SSH sensors. It provides best performance and security. It is set by default in objects that are higher in the hierarchy so usually you can keep the Inherit from parent device (default) option.
• Compatibility Mode (deprecated): Try this legacy method only if the default mode does not work on a target device. The compatibility mode is the SSH engine that PRTG used in previous versions and is deprecated. We will remove this legacy option soon, so please try to get your SSH sensors running with the default SSH engine.

The option you select here overrides the selection of the SSH engine in a higher object (which is a parent device, group, probe, or root).

Result Handling

Define what PRTG will do with the sensor results. Choose between:

• Discard sensor result: Do not store the sensor result.
• Write sensor result to disk (Filename: "Result of Sensor [ID].txt"): Store the last result received from the sensor to the Logs (Sensor) directory in the PRTG data folder on the probe system the sensor is running on (on the Master node if in a cluster). File names: Result of Sensor [ID].txt and Result of Sensor [ID].Data.txt. This is for debugging purposes. PRTG overrides these files with each scanning interval.
  For more information on how to find the folder used for storage,
  see section Data Storage.

This option is not available on cloud probes in PRTG in the cloud.

• Write sensor result to disk (Filename: "Result of Sensor [ID].txt")  in case of error: Store the last result of the sensor only if it throws an error.

This option is not available on cloud probes in PRTG in the cloud.

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel will always be displayed below the sensor's name. The available options depend on what channels are available for this sensor.

You can set another primary channel later by clicking the pin symbol of a channel in the sensor's Overview tab.

Graph Type

Define how different channels will be shown for this sensor.

• Show channels independently (default): Show an own graph for each channel.
• Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This will generate an easy-to-read graph that visualizes the different components of your total traffic.
  This option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channels Settings settings).

Stack Unit

This setting is only available if stacked graphs are selected above. Choose a unit from the list. All channels with this unit will be stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Scanning Interval

Select a scanning interval (seconds, minutes, or hours) from the list. The scanning interval determines the time the sensor waits between two scans. You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Define the number of scanning intervals that a sensor has time reach and check a device again in case a sensor query fails. The sensor can try to re-reach and check a device several times, depending on the option you select here, before it will be set to a Down status. This helps you avoid false alarms if the monitored device has only temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose between:

• Set sensor to "down" immediately: The sensor will show an error immediately after the first failed request.
• Set sensor to "warning" for 1 interval, then set to "down" (recommended): After the first failed request, the sensor will show a yellow warning status. If the following request also fails, the sensor will show an error.
• Set sensor to "warning" for 2 intervals, then set to "down": Show an error status only after three continuously failed requests.
• Set sensor to "warning" for 3 intervals, then set to "down": Show an error status only after four continuously failed requests.
• Set sensor to "warning" for 4 intervals, then set to "down": Show an error status only after five continuously failed requests.
• Set sensor to "warning" for 5 intervals, then set to "down": Show an error status only after six continuously failed requests.

Sensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval until they show an error. It is not possible to set a WMI sensor to "down" immediately, so the first option will not apply to these sensor types. All other options can apply.

If a sensor has defined error limits for channels, it will always show a Down status immediately, so no "wait" option will apply.
 

If a channel uses lookup values, it will always show a Down status immediately, so no "wait" options will apply.

Inheritance for schedules, dependencies, and maintenance windows cannot be interrupted. The corresponding settings from the parent objects will always be active. However, you can define additional settings here. They will be active at the same time as the parent objects' settings.

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days, hours) every week. With the period list option it is also possible to pause monitoring for a specific time span. You can create new schedules and edit existing ones in the account settings.

Schedules are generally inherited. New schedules will be added to existing ones, so all schedules are active at the same time.

Maintenance Window

Specify if you want to set up a one-time maintenance window. During a "maintenance window" period, this object and all child objects will not be monitored. They will be in a paused state instead. Choose between:

• Not set (monitor continuously): No maintenance window will be set and monitoring will always be active.
• Set up a one-time maintenance window: Pause monitoring within a maintenance window. You can define a time span for a monitoring pause below and change it even for a currently running maintenance window.

To terminate a current maintenance window before the defined end date, change the time entry in Maintenance Ends field to a date in the past.

Maintenance Begins

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Maintenance Ends

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the end date and time of the maintenance window.

Dependency Type

Define a dependency type. Dependencies can be used to pause monitoring for an object depending on the status of another. You can choose between:

• Use parent: Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency.
• Select object: Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency. Additionally, pause the current sensor if a specific other object in the device tree is in Down status, or is paused by another dependency. Select below.
• Master object for parent: Make this sensor the master object for its parent device. The sensor will influence the behavior of the device, where it is created on: If the sensor is in Down status, the device will be paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor will be paused if the parent group of its parent device is in Down status, or if it is paused by another dependency.

Testing your dependencies is easy! Simply choose Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later all dependent objects should be paused. You can check all dependencies in your PRTG installation by selecting Devices | Dependencies from the main menu bar.

Dependency

This field is only visible if the Select object option is enabled above. Click on the reading-glasses and use the object selector to choose an object on which the current sensor will depend.

Dependency Delay (Sec.)

Define a time span in seconds for a dependency delay. After the master object for this dependency goes back to Up status, PRTG will start monitoring the depending objects after this extra delayed. This can help to avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Please enter an integer value.

This setting is not available if you choose this sensor to Use parent or to be the Master object for parent. In this case, please define delays in the parent Device Settings or in the superior Group Settings.

User Group Access

Define which user group(s) will have access to the object you're editing. A table with user groups and types of access rights is shown: It contains all user groups from your setup. For each user group you can choose from the following access rights:

• Inherited: Use the access rights settings of the parent object.
• None: Users in this group cannot see or edit the object. The object neither shows up in lists nor in the device tree. Exception: If a child object is visible to the user, the object is visible in the device tree, though not accessible.
• Read: Users in this group can see the object and review its monitoring results.
• Write: Users in this group can see the object, review its monitoring results, and edit the object's settings. They cannot edit access rights settings.
• Full: Users in this group can see the object, review its monitoring results, edit the object's settings, and edit access rights settings.

You can create new user groups in the System Administration—User Groups settings. To automatically set all objects further down in the hierarchy to inherit this object's access rights, set a check mark for the Revert children's access rights to inherited option.

For more details on access rights, please see the section User Access Rights.

Channel Unit Types

For each type of sensor channel, define the unit in which data is displayed. If defined on probe, group, or device level, these settings can be inherited to all sensors underneath. You can set units for the following channel types (if available):

• Bandwidth
• Memory
• Disk
• File
• Custom

Custom channel types can be set on sensor level only.