PRTG Manual: SSH Disk Free Sensor

The SSH Disk Free sensor monitors free space on disks of a Linux/Unix system using Secure Shell (SSH).

The sensor can show the following:

  • Free disk space in bytes for every mounted partition
  • Free disk space in percent for every mounted partition
  • Total disk space

icon-i-roundThe free space returned by this sensor shows the available disk space of the volume, minus a reserve defined for this volume (for example, for redundancy purposes). So, this sensor shows the disk space that is actually available for use. The size of the reserved disk space can be defined with tune2fs. For details, see the Knowledge Base: Why do SSH Disk Free and SNMP Linux Disk Free show different values for my target Linux system?

SSH Disk Free Sensor

SSH Disk Free Sensor

Sensor in Other Languages

Dutch: SSH Disk vrij, French: Espace disque disponible SSH, German: SSH Laufwerkskapazität, Japanese: SSH ディスク空き容量, Portuguese: SSH Disco livre, Russian: Свободное пространство диска по SSH, Simplified Chinese: SSH 磁盘可用空间, Spanish: SSH disco libre

Remarks

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.

Select the disks that you want to monitor. PRTG creates one sensor for each disk that you select in the Add Sensor dialog. The settings you select will be valid for all sensors that you create when you finish this dialog.

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

SSH Disk Free

Disks

Select the partitions that you want to monitor. You see a list with the names of all items that are available for monitoring. Select the desired items by adding check marks in front of the respective lines. PRTG creates two channels for each selection. You can also select and deselect all items by using the check box in the table header.

icon-i-roundYou can select up to 100 disks. If you select more disks, you cannot create the sensor. Add the sensor multiple times to monitor more than 100 disks with several sensors.

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

sshdiskfreesensor, diskfreesensor

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.

Set limits checked FOR ALL disks

In this section, you can set limits that are valid for all channels and all drives. By entering limits, you can define when the sensor will show a Warning or Down status, depending on the data provided by all drives that this sensor monitors. If you want to individually define limits for separate channels, use the limit settings in the Sensor Channel Settings.

icon-i-round-redAll limits that you define here are valid in addition to the limits defined in the particular Channel settings. The limits are valid simultaneously, so the first limit that is breached applies.

Percentage Limit Check

Enable or disable a limit check for the free space in percentage channels of all drives. By default, percentage limits are enabled with lower warning and lower error limit. Choose between:

  • Only use the limits in the settings of the percentage channels: Do not define sensor limits that are valid for all percentage channels. The sensor only uses limits that you define in the settings of the particular "free space in percent" channels to determine the status.
  • Use the limits of both the sensor and the channel settings: Define limits for the sensor that are valid for all drives (percentage channels). Additional fields appear below. The sensor shows a Warning or Down status when free space limits are undercut or overrun.

Upper Error Limit

This field is only visible if you enable Use the limits of both the sensor and the channel settings above. Specify an upper limit in percent for a Down status. If the free disk space of one of your drives overruns this percent value, the sensor will change to a Down status. Enter an integer value or leave the field empty.

icon-i-round-redThe limits set here are valid for all channels of this sensor. You can additionally set individual limits for each sensor channel in the Sensor Channel Settings. The limits set here and in the channel settings are valid simultaneously.

Upper Warning Limit

This field is only visible if you enable Use the limits of both the sensor and the channel settings above. Specify an upper limit in percent for a Warning status. If the free disk space of one of your drives overruns this percent value, the sensor will change to a Warning status. Enter an integer value or leave the field empty.

icon-i-round-redThe limits set here are valid for all channels of this sensor. You can additionally set individual limits for each sensor channel in the Sensor Channel Settings. The limits set here and in the channel settings are valid simultaneously.

Lower Warning Limit

This field is only visible if you enable Use the limits of both the sensor and the channel settings above. Specify a lower limit in percent for a Warning status. If the free disk space of one of your drives undercuts this percent value, the sensor will change to a Warning status. Enter an integer value or leave the field empty.

icon-i-round-redThe limits set here are valid for all channels of this sensor. You can additionally set individual limits for each sensor channel in the Sensor Channel Settings. The limits set here and in the channel settings are valid simultaneously.

Lower Error Limit

This field is only visible if you enable Use the limits of both the sensor and the channel settings above. Specify a lower limit in percent for a Down status. If the free disk space of one of your drives undercuts this percent value, the sensor will change to a Down status. Enter an integer value or leave the field empty.

icon-i-round-redThe limits set here are valid for all channels of this sensor. You can additionally set individual limits for each sensor channel in the Sensor Channel Settings. The limits set here and in the channel settings are valid simultaneously.

Size Limit Check

Enable or disable a limit check for the free bytes channels of all drives. By default, byte size limits are not enabled for drives. Choose between:

  • Only use the limits in the settings of the byte size channels: Do not define sensor limits that are valid for all byte size channels. The sensor only uses limits that you define in the settings of the particular free space in bytes channels to determine the status.
  • Use the limits of both the sensor and the channel settings: Define limits for the sensor that are valid for all drives (byte size channels). Additional fields appear below. The sensor shows a Warning or Down status when free space limits are undercut or overrun.

Upper Error Limit

This field is only visible if you enable Use the limits of both the sensor and the channel settings above. Specify an upper limit. Use the same unit as shown by the free bytes channels of this sensor (by default this is MB). If the free disk space of one of your drives overruns this bytes value, the sensor will change to a Down status. Enter an integer value or leave the field empty.

icon-i-round-redThe limits set here are valid for all channels of this sensor. You can additionally set individual limits for each sensor channel in the Sensor Channel Settings. The limits set here and in the channel settings are valid simultaneously.

Upper Warning Limit

This field is only visible if you enable Use the limits of both the sensor and the channel settings above. Specify an upper limit. Use the same unit as shown by the free bytes channels of this sensor (by default this is MB). If the free disk space of one of your drives overruns this bytes value, the sensor will change to a Warning status. Enter an integer value or leave the field empty.

icon-i-round-redThe limits set here are valid for all channels of this sensor. You can additionally set individual limits for each sensor channel in the Sensor Channel Settings. The limits set here and in the channel settings are valid simultaneously.

Lower Warning Limit

This field is only visible if you enable Use the limits of both the sensor and the channel settings above. Specify a lower limit. Use the same unit as shown by the free bytes channels of this sensor (by default this is MB). If the free disk space of one of your drives undercuts this bytes value, the sensor will change to a Warning status. Enter an integer value or leave the field empty.

icon-i-round-redThe limits set here are valid for all channels of this sensor. You can additionally set individual limits for each sensor channel in the Sensor Channel Settings. The limits set here and in the channel settings are valid simultaneously.

Lower Error Limit

This field is only visible if you enable Use the limits of both the sensor and the channel settings above. Specify a lower limit. Use the same unit as shown by the free bytes channels of this sensor (by default this is MB). If the free disk space of one of your drives undercuts this bytes value, the sensor will change to a Down status. Enter an integer value or leave the field empty.

icon-i-round-redThe limits set here are valid for all channels of this sensor. You can additionally set individual limits for each sensor channel in the Sensor Channel Settings. The limits set here and in the channel settings are valid simultaneously.

Alarm on Missing/Removed Disk

If a monitored disk is removed or not found, values are set to zero. Select the alarming approach in this case. Choose between:

  • Deactivate alarm (default): Select this option if you do not want an alarm for a removed disk.
  • Activate alarm: Select this option if you want to be alerted if a monitored disk is removed.

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.

More

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

Knowledge Base: SSH and SFTP Sensors in Unknown Status

Knowledge Base: How do I set up SSH sensors with my AWS Linux instances?

Knowledge Base: Why do SSH Disk Free and SNMP Linux Disk Free show different values for my target Linux system?

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: