<%NUMBERING1%>.<%NUMBERING2%>.<%NUMBERING3%> PRTG Manual: SSH Script Sensor

The SSH Script sensor connects to a Linux/Unix system via Secure Shell (SSH) and executes a script file located on the target system. This option is provided as part of the PRTG application programming interface (API).

The sensor can show the following:

  • Execution time
  • One value returned by the executable file or script (in one channel only)

icon-book-arrowsFor details about the return value format, see section Custom Sensors.

SSH Script Sensor

SSH Script Sensor

Sensor in Other Languages

Dutch: SSH Script, French: Script SSH, German: SSH-Skript, Japanese: SSH スクリプト実行, Portuguese: SSH Script, Russian: Скрипт SSH, Simplified Chinese: SSH 脚本, Spanish: Secuencia de comandos de SSH

Remarks

  • This sensor can have a high impact on the performance of your monitoring system. Use it with care. We recommend that you use no more than 50 sensors of this sensor type on each probe.
  • For security reasons, you must store your script file on the target system. The file must be located in the directory /var/prtg/scripts. Make sure that the script has executable rights. If the script is not available or was deleted from the script folder, you will get the error message Script not found (237).
  • Requires Credentials for Linux/Solaris/Mac OS (SSH/WBEM) systems on the device that you want to use the sensor on.
  • This sensor cannot support all Linux/Unix and macOS distributions.
  • For details about the return value format, see section Custom Sensors.
  • Knowledge Base: SSH and SFTP Sensors in Unknown Status

Add Sensor

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you will not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

The following settings in the Add Sensor dialog differ in comparison to the sensor's Settings tab.

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. 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.

icon-book-arrowsFor detailed information on the expected return format and on how to build custom sensors, see section Custom Sensors.

icon-book-bulbFor an example script, see the Knowledge Base: Is there a shell script example for the PRTG SSH Script Sensor?

Value Type

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

  • Integer: The return values are of the type integer. If the script returns a float, PRTG will show 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 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.
    icon-i-roundA counter must return an integer, float values are not supported.

icon-i-roundThis 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 Settings

On the details page of a sensor, click the Settings tab to change its settings.

icon-i-roundUsually, a sensor connects to the IP Address or DNS Name of the parent device on which you created the sensor. See the Device Settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings. See below for details on available settings.

Basic Sensor 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.

There are default tags that are automatically predefined in a sensor's settings when you add a sensor. See section Default Tags below.

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.

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

Priority

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

Default Tags

sshscript

Sensor Settings

Script

Shows the name of the script that the sensor executes with each scan. Once you have created a sensor, you cannot change this value. It is shown for reference purposes only. If you need to change this value, 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. Enter a string or leave the field empty.

icon-book-arrowsFor a full list of all placeholders, see section Custom Sensors.

icon-i-round-redYou 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 will run all custom script sensors that have the same mutual exclusion (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.

icon-book-bulbSee the Knowledge Base: What is the Mutex Name in the PRTG EXE/Script Sensor settings?

Unit String

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

If Value Changes

Define what this sensor will do when the sensor value changes. 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.

SSH Specific

Connection Timeout (Sec.)

Define a timeout in seconds for the connection. This is the time that 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). Enter an integer value.

icon-i-roundThe 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 will not have an effect on the timeout.

icon-i-blueEnsure 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 will wait 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.

icon-i-roundThe 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 will not have an effect on the timeout.

icon-i-blueEnsure 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. 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 enable Enter custom port number above. Enter the port number (between 1 and 65535) that this sensor will use 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 option soon, so try to get your SSH sensors running with the default SSH engine.

icon-i-round-redThe 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 will do with the sensor results. Choose between:

  • Discard sensor result: Do not store the sensor result.
  • Write sensor result to disk (File name: Result of Sensor [ID].txt): Store the last result received from the sensor to the Logs (Sensors) subfolder of the PRTG data directory 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 overwrites these files with each scanning interval. icon-book-arrows
    For more information on how to find the folder used for storage, see section Data Storage.
    icon-prtg-on-demandThis option is not available when the sensor runs on the Hosted Probe of a PRTG hosted by Paessler instance.
  • Write sensor result to disk (File name: "Result of Sensor [ID].txt") in case of error: Store the last result of the sensor only if it throws an error.
    icon-prtg-on-demandThis option is not available when the sensor runs on the Hosted Probe of a PRTG hosted by Paessler instance.

Sensor Display

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.

icon-i-roundYou can set a different primary channel later by clicking the pin symbol of a channel on the sensor's Overview tab.

Graph Type

Define how different channels will be 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 will generate a graph that visualizes the different components of your total traffic.
    icon-i-roundThis option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channel Settings settings).

Stack Unit

This field is only visible if you enable Stack channels on top of each other above. Select 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.

Inherited Settings

By default, all of the following settings are inherited from objects that are higher in the hierarchy and should be changed there if necessary. Often, best practice is to change them centrally in the Root group's settings. For more information, see section Inheritance of Settings. To change a setting for this object only, disable inheritance by clicking the button next to inherit from under the corresponding setting name. You will then see the options described below.

Scanning Interval

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

Scanning Interval

Select a scanning interval (seconds, minutes, or hours). The scanning interval determines the amount of time that 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 the sensor has time to reach and check a device again in case a sensor query fails. Depending on the option that you select, the sensor can try to reach and check a device again several times before the sensor will show a Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose from:

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

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

icon-i-roundIf you define error limits for a sensor's channels, the sensor will immediately show a Down status. No "wait" option will apply.

icon-i-roundIf a channel uses lookup values, the sensor will immediately show a Down status. No "wait" options will apply.

Schedules, Dependencies, and Maintenance Window

icon-i-roundYou cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. 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 or hours) every week.

icon-book-arrowsYou can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Account Settings—Schedules.

icon-i-roundSchedules are generally inherited. New schedules will be added to existing schedules, 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, the current sensor and all child objects will not be monitored. They will be in a Paused status 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.

icon-i-roundTo terminate a current maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.

Maintenance Begins

This field 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 maintenance window.

Maintenance Ends

This field 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 maintenance window.

Dependency Type

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

  • Use parent: Use the dependency type of the parent device.
  • Select a sensor: Use the dependency type of the parent device. Additionally, pause the current sensor if another specific sensor is in a Down status or in a Paused status caused by another dependency. Select below.
  • Master sensor for parent: Make this sensor the master object for its parent device. The sensor will influence the behavior of its parent device: If the sensor is in a 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 is paused by another dependency.

icon-i-roundTo 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 will 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 you enable Select a sensor above. Click the Search button and use the object selector to select a sensor on which the current sensor will depend.

Dependency Delay (Sec.)

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

After the master sensor for this dependency comes back to an Up status, monitoring of the dependent objects will be additionally delayed by the defined time span. This can help avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Enter an integer value.

icon-i-round-redThis 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.

Access Rights

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

User Group Access

Define the user groups that will have access to the selected object. 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 but it cannot be accessed.
  • 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 its settings. They cannot edit access rights settings.
  • Full: Users in this group can see the object, review its monitoring results, edit its 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.

icon-book-arrowsFor more details on access rights, see section User Access Rights.

Channel Unit Configuration

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

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

icon-i-roundCustom channel types can be set on sensor level only.

Escape Special Characters and Whitespaces in Parameters

icon-toolsYou need to escape special characters in parameters that you pass to an executable or script and surround them with quotation marks to make sure that the characters are correctly interpreted. PowerShell scripts in particular require adequate escaping so that the parameters are passed in a valid PowerShell syntax. To make escaping easy and secure, PRTG automatically does most of the escaping for you.

Follow these rules to escape special characters and whitespaces in the parameters fields:

  • Use quotes for parameters that contain whitespaces.

-name "Mr John Q Public"
-name 'Mr John Q Public' 

  • Use double quotes for parameters that contain single quotes.

-name "Mr 'John Q' Public"

  • Use single quotes for parameters that contain double quotes.

-name 'Mr "John Q" Public'

  • Use a backslash (\) to escape and pass a literal double quote.

-name pub\"lic

  • Use double quotes for parameters that contain double and single quotes and escape double quotes.

-name "pu'b\"lic"

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

icon-i-blueWe recommend that you do not pass passwords in parameters. Use PRTG placeholders instead. See section Custom Sensors for details.

More

PRTG Manual:

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

Knowledge Base: How and where does PRTG store its data?

Knowledge Base: How can I test if parameters are correctly transmitted to my script when using an EXE/Script sensor?

Knowledge Base: For which sensor types do you recommend Windows Server 2012 R2 or later and why?

Knowledge Base: How can I show special characters with EXE/Script sensors?

Knowledge Base: Why do I have to store SQL sensor queries and custom scripts in files on the probe computer?

Knowledge Base: Is there a shell script example for the PRTG SSH Script Sensor?

Knowledge Base: SSH and SFTP Sensors in Unknown Status

Edit Sensor Channels

To change display settings, spike filtering, and limits, switch to the sensor's Overview tab and click the gear icon of a specific channel. For detailed information, see section Sensor Channel Settings.

Notification Triggers

Click the Notification Triggers tab to change notification triggers. For detailed information, see section Sensor Notification Triggers Settings.

Others

For more general information about settings, see section Object Settings.

Sensor Settings Overview

For information about sensor settings, see the following sections:

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