After several power outages I finally decided to by a small UPS (USV) for my homelab. I don’t like when my IT infrastructur, especially the Synology NAS, gets switched off without a normal shutdown. So I bought a new EATON 5P 650 UPS to cover my NAS and server.

I started trying to use the Synology Diskstation as a NUT server. Usually the NAS can do this by default. You just attache the UPS via usb to the NAS and activate the function. Everything seems working fine. The problem was, it works locally. But you could not connect to the NUT server from another machine. I tried to connect from an ESXi 6.7 U3 host with installed NUT-Client and from an Windows Server 2019, both couldn’t connect. The ESXi hosts said „Error: Access denied“ so I tried to connect via telnet.

telnet nut-server-ip-address 3493

With telnet I get a connection, but when it comes to login with the username, there is also an access denied. After many hours trying to fix thie access problem I gave up. The funny thing is, after all this I setup a new NUT Server on an Debian VM in under 15 min.

NUT package (nutd and upsmon)

  1. Plug-In the UPS USB-Connection to the host. In my case I connected it to the ESXi host and configured a this new virtual usb device in the Debain VM. You also can use a normal computer with Debian 10 installed.
  2. Install the NUT package with the apt package manager
    sudo apt-get install nut
  3. Make some configurations and changes in the nut directory /etc/nut
    # /etc/nut/
    drwxr-xr-x 2  root nut  4096   Jan 11 00:49 .
    drwxr-xr-x 94 root root 4096   Jan 10 23:54 ..
    -rw-r----- 1  root nut  1543   Jan 11 00:01 nut.conf
    -rw-r----- 1  root nut  5571   Jan 11 00:12 ups.conf
    -rw-r----- 1  root nut  4595   Jan 11 00:01 upsd.conf
    -rw-r----- 1  root nut  2177   Jan 11 00:03 upsd.users
    -rw-r----- 1  root nut  15362  Jan 11 00:16 upsmon.conf
    -rw-r----- 1  root nut  3887   Jun  1  2018 upssched.conf
  4. In the nut.conf file we change the MODE to netserver
    # /etc/nut/nut.conf
  5. In the ups.conf we need to configure the right drivers for the UPS. In my case I knew what to configure, because the Synology NAS made the right configuration. You can get a compatibility list from the NUT-Server on
    We make a new section for the UPS like in this example. As my UPS is connected via usb the port configuration can be set to auto. If you connect the UPS via a serial cable you need to configure it different.

    # /etc/nut/ups.conf
        driver = usbhid-ups
        port = auto

    The name in the brackets can be anything you like to identify the ups. I used eaton as the name related to the manufacturer. In bigger setups you may like to name it like [serverups] …
    After setting up the right drivers we can make sure that the NUT-Server detects the UPS.

    upsdrvctl start

    The output should look like this

    Network UPS Tools - UPS driver controller 2.7.4
    Network UPS Tools - Generic HID driver 0.41 (2.7.4)
    USB communication driver 0.33
  6. The upsd.conf has a LISTEN section. We need to configure it with the server ip-address so we can connect to the NUT-Server from other clients.
    # /etc/nut/upsd.conf
    LISTEN 3493
    LISTEN ::1 3493

    In my example I’ve added the first ip-address ( There is no need to write the port behind the address (3493) unless you want to change the default port.

  7. After that we need to make a new user in the upsd.user file
    # /etc/nut/upsd.user
           password = supersecretpassword
           upsmon master

    You should add multiple users for the server an client. See the man page for upsd.users for more information.

  8. Now we configure the upsmon.conf there we need to add a MONITOR master
    # /etc/nut/upsmon.conf
    # MONITOR     ("master"|"slave")
    #  is an integer - the number of power supplies that this UPS
    # feeds on this system. Most computers only have one power supply, so this
    # is normally set to 1. You need a pretty big or special box to have any
    # other value here.
    MONITOR eaton@ 1 monuser supersecretpassword master
    POWERDOWNFLAG /etc/killpower
    SHUTDOWNCMD "/sbin/shutdown -h now"

    As the system name us us the value in the brackets you made in the ups.conf the user and password was configured in the upsd.user file.

  9. Since we don’t want that other users can read this secret files we fix the permissions for our needs.
    $ sudo chown root:nut /etc/nut/*
    $ sudo chmod 640 /etc/nut/*
  10. At the end whe should reload both services upsd and upsmon. This can be done like this

Testing a local Client request

  1. Now we can test if the NUT-Server works locally. In my case the name of my instance is [eaton]. Therfore I’ll make client request to this the instance name eaton.
    upsc eaton

    If everything works fine we get an output similar like this

    Init SSL without certificate database
    battery.capacity: 9.00
    battery.charge: 100
    battery.charge.low: 20
    battery.charge.restart: 0
    battery.charger.status: floating
    battery.energysave: no
    battery.energysave.delay: 300
    battery.energysave.load: 5 yes
    battery.runtime: 1575
    battery.type: PbAc
    battery.voltage: 13.7
    battery.voltage.nominal: 12
    device.mfr: EATON
    device.model: 5P 650
    device.serial: G114L41071
    device.type: ups usbhid-ups
    driver.parameter.pollfreq: 30
    driver.parameter.pollinterval: 2
    driver.parameter.port: auto
    driver.parameter.synchronous: no
    driver.version: 2.7.4 MGE HID 1.39
    driver.version.internal: 0.41
    input.current: 0.70
    input.frequency: 49.9
    input.frequency.extended: no
    input.frequency.nominal: 50
    input.sensitivity: normal
    input.transfer.boost.low: 184
    input.transfer.high: 294
    input.transfer.low: 160
    input.transfer.trim.high: 265
    input.voltage: 235.9
    input.voltage.extended: no
    input.voltage.nominal: 230
    outlet.1.autoswitch.charge.low: 0
    outlet.1.delay.shutdown: 65535
    outlet.1.delay.start: 3
    outlet.1.desc: PowerShare Outlet 1 1
    outlet.1.status: on
    outlet.1.switchable: yes
    outlet.2.autoswitch.charge.low: 0
    outlet.2.delay.shutdown: 65535
    outlet.2.delay.start: 6
    outlet.2.desc: PowerShare Outlet 2 2
    outlet.2.status: on
    outlet.2.switchable: yes
    outlet.desc: Main Outlet 0
    outlet.switchable: no
    output.current: 0.60
    output.frequency: 49.9
    output.frequency.nominal: 50
    output.powerfactor: 0.53
    output.voltage: 235.9
    output.voltage.nominal: 230
    ups.beeper.status: enabled
    ups.delay.shutdown: 20
    ups.delay.start: 30
    ups.efficiency: 86
    ups.firmware: 02.14.0026
    ups.load: 21
    ups.load.high: 105
    ups.mfr: EATON
    ups.model: 5P 650
    ups.power: 142
    ups.power.nominal: 650
    ups.productid: ffff
    ups.realpower: 76
    ups.realpower.nominal: 420
    ups.serial: G114L41071
    ups.shutdown: enabled yes
    ups.start.battery: yes
    ups.start.reboot: yes
    ups.status: OL CHRG
    ups.test.interval: 2592000
    ups.test.result: Done and passed
    ups.timer.shutdown: 0
    ups.timer.start: 0
    ups.type: offline / line interactive
    ups.vendorid: 0463

I hope I could help you make a basic NUT-Server setup for your homelab.

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