PRTG Manual: SSH Script Sensor

Script

Select a script file from the dropdown list. It shows 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 in this directory. Make sure that 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, see section Custom Sensors.

For an example script, see the Knowledge Base: Is there a shell script example for the SSH Script sensor?

Value Type

Define the type of the values that your script returns:

• Integer: The return values are of the type integer. If the script returns a float, PRTG shows the value 0.
• Float: The return values are of the type float, with a dot (.) between predecimal position and decimal places. With this setting, the sensor also displays integer values unless they produce a buffer overflow.
• Counter: Your script returns varying integer values. PRTG shows the difference between the values of two sensor scans.
  A counter must return an integer, float values are not supported.

This sensor does not support string values.

Channel Name

Enter a name for the channel in which the sensor shows returned values. 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.

If the name contains angle brackets (<>), PRTG replaces them with braces ({}) for security reasons. For more information, see the Knowledge Base: What security features does PRTG include?

Parent Tags

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

Tags

Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited.

It is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).

The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:

• sshscript

Priority

Select a priority for the sensor. This setting determines the position of the sensor in lists. The highest priority is at the top of a list. Choose from the lowest priority () to the highest priority ().

Script

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

Character Encoding

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

• UTF-8 (default)
• ASCII

Parameters

If your script file catches command-line parameters, you can define them here. You can use placeholders as well. Enter a string or leave the field empty.

For a full list of all placeholders, see section Custom Sensors.

You need to escape special characters and whitespaces in your parameters and surround them with double quotes. See section Escape Special Characters and Whitespaces in Parameters for details.

In SSH scripts, you can use alphanumeric characters and the special characters ".", "_", "-", "=", and "/" outside of quoted strings.

Mutex Name

Define any desired mutual exclusion (mutex) name for the process. PRTG runs all custom script sensors that have 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. Enter a string or leave the field empty.

See the Knowledge Base: What is the Mutex Name in the PRTG EXE/Script settings?

Unit String

Define a unit for the channel value. Enter a string. This is for display purposes only and is 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 you have created the sensor, you cannot change this value. It is shown for reference purposes only. If you need to change this value, add the sensor anew.

If Value Changes

Define what the sensor does when the sensor value changes:

• Ignore changes (default): Take no action on change.
• Trigger 'change' notification: Send an internal message indicating that the sensor 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 that the sensor waits to establish a connection to the host. Keep this value as low as possible. The maximum value is 900 seconds (15 minutes). Enter an integer value.

The sensors SSH SAN Enclosure, SSH SAN Logical Disk, SSH SAN Physical Disk, and SSH SAN System Health have a fixed timeout of 300 seconds. Changing the value here does not have an effect on the timeout.

Ensure that the connection timeout is a value that is higher than the shell timeout to avoid potential errors.

Shell Timeout (Sec.)

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

The sensors SSH SAN Enclosure, SSH SAN Logical Disk, SSH SAN Physical Disk, and SSH SAN System Health have a fixed timeout of 300 seconds. Changing the value here does not have an effect on the timeout.

Ensure that the shell timeout is a value that is lower than the connection timeout to avoid potential errors.

SSH Port

Define which port this sensor uses for the SSH connection:

• Inherit port number from parent device (default): Use the port number as defined in the Credentials for Linux/Solaris/macOS (SSH/WBEM) Systems section of the parent device settings.
• 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 setting is only visible if you enable Enter custom port number above. Enter the port number (between 1 and 65535) that this sensor uses for the SSH connection. Enter an integer value.

SSH Engine

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

• Inherit from parent device (default): Use the SSH engine that you defined in the parent device settings or higher up in the object hierarchy. If you have not changed the SSH engine, this is the recommended default engine.
• Default: This is the default monitoring method for SSH sensors. It provides the best performance and security. It is set by default in objects that are higher up 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. It is deprecated. We will remove this legacy mode soon, so 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: a parent device, group, probe, or root.

Result Handling

Define what PRTG does with the sensor result:

• Discard result: Do not store the sensor result.

• Store result: Store the last sensor result in the \Logs\sensors subfolder of the PRTG data directory on the probe system. The file names are Result of Sensor [ID].txt, Result of Sensor [ID].Data.txt, and Result of Sensor [ID] (SSHv2).txt. This setting is for debugging purposes. PRTG overwrites these files with each scanning interval.

• Store result in case of error: Store the last sensor result only if the sensor shows the Down status.

This option is not available when the sensor runs on the hosted probe of a PRTG hosted by Paessler instance.

In a cluster, PRTG stores the result in the PRTG data directory of the master node.

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 is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.

You can set a different primary channel later by clicking below a channel gauge on the sensor's Overview tab.

Graph Type

Define how different channels are shown for this sensor:

• Show channels independently (default): Show a 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 generates a graph that visualizes the different components of your total traffic.
  You cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This setting is only visible if you enable Stack channels on top of each other as Graph Type. Select a unit from the list. All channels with this unit are 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 from the dropdown list. The scanning interval determines the amount of time that the sensor waits between two scans. Choose from:

• 30 seconds
• 60 seconds
• 5 minutes
• 10 minutes
• 15 minutes
• 30 minutes
• 1 hour
• 4 hours
• 6 hours
• 12 hours
• 1 day

You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Select the number of scanning intervals that the sensor has time to reach and to check a device again if a sensor query fails. Depending on the option that you select, the sensor can try to reach and to check a device again several times before the sensor shows the Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor shows the Warning status. Choose from:

• Set sensor to down immediately: Set the sensor to the Down status immediately after the first request fails.
• Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to the Warning status after the first request fails. If the second request also fails, the sensor shows the Down status.
• Set sensor to warning for 2 intervals, then set to down: Set the sensor to the Down status only after the third request fails.
• Set sensor to warning for 3 intervals, then set to down: Set the sensor to the Down status only after the fourth request fails.
• Set sensor to warning for 4 intervals, then set to down: Set the sensor to the Down status only after the fifth request fails.
• Set sensor to warning for 5 intervals, then set to down: Set the sensor to the Down status only after the sixth request fails.

Sensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval before they show the Down status. It is not possible to immediately set a WMI sensor to the Down status, so the first option does not apply to these sensors. All other options can apply.

If you define error limits for a sensor's channels, the sensor immediately shows the Down status. None of the interval options apply.

If a channel uses lookup values, the sensor immediately shows the Down status. None of the interval options apply.

Schedule

Select a schedule from the list. You can use schedules to monitor during a certain time span (days or hours) every week. Choose from:

• None
• Saturdays
• Sundays
• Weekdays
• Weekdays Eight-To-Eight (08:00 - 20:00)
• Weekdays Nights (17:00 - 09:00)
• Weekdays Nights (20:00 - 08:00)
• Weekdays Nine-To-Five (09:00 - 17:00)
• Weekends

You can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Schedules.

Maintenance Window

Select if you want to set up a one-time maintenance window. During a maintenance window, monitoring stops for the selected object and all child objects. They show the Paused status instead. Choose between:

• Do not set up a one-time maintenance window: Do not set up a one-time maintenance window. Monitoring is always active.
• Set up a one-time maintenance window: Set up a one-time maintenance window and pause monitoring. You can define a time span for a the pause below.

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

Maintenance Begins

This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the one-time maintenance window.

Maintenance Ends

This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the end date and time of the one-time maintenance window.

Dependency Type

Select a dependency type. You can use dependencies to pause monitoring for an object depending on the status of a different object. You can choose from:

• Use parent: Use the dependency type of the parent object.
• Select a sensor: Use the dependency type of the parent object. Additionally, pause the current object if a specific sensor is in the Down status or in the Paused status because of another dependency.

• Master sensor for parent: Make this sensor the master object for its parent device. The sensor influences the behavior of its parent device: If the sensor is in the Down status, the device is 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 is paused if the parent group is paused by another dependency.

To test your dependencies, select Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later, all dependent objects are paused. You can check all dependencies under Devices | Dependencies in the main menu bar.

Dependency

This setting is only visible if you enable Select a sensor above. Click and use the object selector to select a sensor on which the current object will depend.

Dependency Delay (Sec.)

This setting is only visible if you enable Select a sensor above. Define a time span in seconds for the dependency delay.

After the master sensor for this dependency returns to the Up status, PRTG additionally delays the monitoring of the dependent objects by the time span you define. This can prevent false alarms, for example, after a server restart or to give systems more time for all services to start. Enter an integer value.

This setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, define delays in the parent device settings or in its parent group settings.

User Group Access

Define the user groups that have access to the sensor. You see a table with user groups and group access rights. The table contains all user groups in your setup. For each user group, you can choose from the following group access rights:

• Inherited: Inherit the access rights settings of the parent object.
• No access: Users in this user group cannot see or edit the sensor. The sensor neither shows up in lists nor in the device tree.
• Read access: Users in this group can see the sensor and view its monitoring results. They cannot edit any settings.
• Write access: Users in this group can see the sensor, view its monitoring results, and edit its settings. They cannot edit its access rights settings.
• Full access: Users in this group can see the sensor, view its monitoring results, edit its settings, and edit its access rights settings.

For more details on access rights, see section Access Rights Management.

Channel Unit Types

For each type of channel, select the unit in which PRTG displays the data. If you define this setting 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 are only available on sensor level.

Downtime

In the channel table on the Overview tab, this channel never shows any values. PRTG uses this channel in graphs and reports to show the amount of time in which the sensor was in the Down status in percent.

Execution Time

The execution time in milliseconds (msec)

This channel is the primary channel by default.

[Value]

The value that the script file returns in one channel

For details about the return value format, see section Custom Sensors.