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ups.conf - UPS definitions for Network UPS Tools


This file is read by the driver controller upsdrvctl(8), the UPS drivers that use the common core (see nutupsdrv(8), and upsd(8)). The file begins with global directives, and then each UPS has a section which contains a number of directives that set parameters for that UPS.

A UPS section begins with the name of the UPS in brackets, and continues until the next UPS name in brackets or until EOF. The name "default" is used internally in upsd, so you can’t use it in this file.

You must define the driver and port elements for each entry. Anything after that in a section is optional. A simple example might look like this:

        driver = blazer_ser
        port = /dev/ttyS0
        desc = "Web server UPS"

A slightly more complicated version includes some extras for the hardware-specific part of the driver:

        driver = apcsmart
        port = /dev/cua00
        cable = 940-0095B
        sdtype = 2
        desc = "Database server UPS"

In this case, the apcsmart(8) driver will receive variables called "cable" and "sdtype" which have special meanings. See the man pages of your driver(s) to learn which variables are supported and what they do.


Optional. The driver will chroot(2) to this directory during initialization. This can be useful when securing systems.


Optional. Path name of the directory in which the UPS driver executables reside. If you don’t specify this, the programs look in a built-in default directory, which is often /usr/local/ups/bin.


Optional. Same as the UPS field of the same name, but this is the default for UPSes that don’t have the field.


Optional. Specify the number of attempts to start the driver(s), in case of failure, before giving up. A delay of retrydelay is inserted between each attempt. Caution should be taken when using this option, since it can impact the time taken by your system to start.

The default is 1 attempt.


Optional. Specify the delay between each restart attempt of the driver(s), as specified by maxretry. Caution should be taken when using this option, since it can impact the time taken by your system to start.

The default is 5 seconds.


Optional. The status of the UPS will be refreshed after a maximum delay which is controlled by this setting. This is normally 2 seconds. This may be useful if the driver is creating too much of a load on your system or network.


Optional. The driver work by default in asynchronous mode (i.e synchronous=no). This means that all data are pushed by the driver on the communication socket to upsd (Unix socket on Unix, Named pipe on Windows) without waiting for these data to be actually consumed. With some HW, such as ePDUs, that can produce a lot of data, asynchronous mode may cause some congestion, resulting in the socket to be full, and the driver to appear as not connected. In such case, the driver will provide the following debug message:

write XX bytes to socket Y failed

By enabling the synchronous flag (value = yes), the driver will wait for data to be consumed by upsd, prior to publishing more. This can be enabled either globally or per driver.

The default is no (i.e. asynchronous mode) for backward compatibility of the driver behavior.




Required. This specifies which program will be monitoring this UPS. You need to specify the one that is compatible with your hardware. See nutupsdrv(8) for more information on drivers in general and pointers to the man pages of specific drivers.


Required. This is the serial port where the UPS is connected. On a Linux system, the first serial port usually is /dev/ttyS0. On FreeBSD and similar systems, it probably will be /dev/cuaa0.


Optional. When you have multiple UPSes on your system, you usually need to turn them off in a certain order. upsdrvctl shuts down all the 0s, then the 1s, 2s, and so on. To exclude a UPS from the shutdown sequence, set this to -1.

The default value for this parameter is 0.


Optional. This allows you to set a brief description that upsd will provide to clients that ask for a list of connected equipment.


Optional. When you specify this, the driver skips the port locking routines every time it starts. This may allow other processes to seize the port if you start more than one accidentally.


This may be needed on Mac OS X systems.


Optional. When you specify this, the driver ignores a low battery condition flag that is reported by the UPS (some devices will switch off almost immediately after setting this flag, or will report this as soons as the mains fails). Instead it will use either of the following conditions to determine when the battery is low:

battery.charge < battery.charge.low
battery.runtime < battery.runtime.low

The idea is to set the battery.charge.low and/or battery.runtime.low levels in ups.conf to a value that gives enough time to cleanly shutdown your system:

override.battery.charge.low = 30
override.battery.runtime.low = 180

In order for this to work, your UPS should be able to (reliably) report charge and/or runtime remaining on battery. Use with caution!


Optional. This can be set as a global variable above your first UPS definition and it can also be set in a UPS section. This value controls how long upsdrvctl will wait for the driver to finish starting. This keeps your system from getting stuck due to a broken driver or UPS.

The default is 45 seconds.


Optional. Same as the global directive of the same name, but this is for a specific device.


Optional. Force the USB code to call usb_set_altinterface(0), as was done in NUT 2.7.2 and earlier. This should not be necessary, since the default for bAlternateSetting (as shown in lsusb) is zero on all USB devices seen to date. However, this redundant call to usb_set_altinterface() prevents certain UPSes from working on Mac OS X. If your UPS requires explicitly setting the alternate interface, include this flag, and email the nut-upsdev list with details about your UPS and operating system.


Optional. Set a default value for <variable> which is used in case the UPS doesn’t provide a value, but will be overwritten if a value is available from the UPS:

default.input.voltage.nominal = 230

The above will report the nominal input voltage to be 230, unless the UPS tells us differently.


Optional. Set a value for <value> that overrides any value that may be read from the UPS. Used for overriding values from the UPS that are clearly wrong (some devices report wrong values for battery voltage for instance):

override.battery.voltage.nominal = 12

Use with caution! This will only change the appearance of the variable to the outside world, internally in the UPS the original value is used.

All other fields are passed through to the hardware-specific part of the driver. See those manuals for the list of what is allowed.



The drivers themselves also obtain configuration data from this file. Each driver looks up its section and uses that to configure itself.

upsd(8) learns about which UPSes are installed on this system by reading this file. If this system is called "doghouse" and you have defined a UPS in your ups.conf called "snoopy", then you can monitor it from upsc(8) or similar as "snoopy@doghouse".



Internet resources

The NUT (Network UPS Tools) home page:
12/29/2015 Network UPS Tools 2.7.3.