8. NUT outlets management and PDU notes

NUT supports advanced outlets management for any kind of device that proposes it. This chapter introduces how to manage outlets in general, and how to take advantage of the provided features.

8.1. Introduction

Outlets are the core of Power Distribution Units. They allow you to turn on, turn off or cycle the load on each outlet.

Some UPS models also provide manageable outlets (Eaton, MGE, Powerware, Tripplite, …) that help save power in various ways, and manage loads more intelligently.

Finally, some devices can be managed in a PDU-like way. Consider blade systems: the blade chassis can be controlled remotely to turn on, turn off or cycle the power on individual blade servers.

NUT allows you to control all these devices!

8.2. NUT outlet data collection

NUT provides a complete and uniform integration of outlets related data, through the outlet collection.

First, there is a special outlet, called main outlet. You can access it through outlet.{id, desc, …} without any index.

Any modification through the main outlet will affect all outlets. For example, calling the command outlet.load.cycle will cycle all outlets.

Next, outlets index starts from 1. Index 0 is implicitly reserved to the main outlet. So the first outlet is outlet.1.*.

For a complete list of outlet data and commands, refer to the NUT command and variable naming scheme.

An example upsc output (data/epdu-managed.dev) is available in the source archive.


The variables supported depend on the exact device type.

8.3. Outlets on PDU

Smart Power Distribution Units provide at least various meters, related to current, power and voltage.

Some more advanced devices also provide control through the load.off, load.on and load.cycle commands.

8.4. Outlets on UPS

Some advanced Uninterruptible Power Supplies provide smart outlet management.

This allows to program a limited backup time to non-critical loads in order to keep the maximum of the battery reserve for critical equipment.

This also allows the same remote electrical management of devices provided by PDUs, which can be very interesting in Data Centers.

For example, on small setup, you can plug printers, USB devices, hubs, (…) into managed outlets. Depending on your UPS’s capabilities, you will be able to turn off those loads:

  • after some minutes of back-up time using outlet.n.delay.start,
  • when reaching a percentage battery charge using outlet.n.autoswitch.charge.low.

This will ensure a maximum runtime for the computer.

On bigger systems, with bigger UPSs, this is the same thing with servers instead of small devices.


If you need the scheduling function and your device doesn’t support it, you can still use NUT scheduling features.


don’t plug the UPS’s communication cable (USB or network) on a managed outlet. Otherwise, all computers will be stopped as soon as the communication is lost.

8.5. Other type of devices

As mentioned in the introduction, some other devices can be considered and managed like PDUs. This is the case in most blade systems, where the blade chassis offers power management services.

This way, you can control remotely each blade server as if it were a PDU outlet.

This category of devices is generally called Remote Power Controls - RPC in NUT.