Accidentally broke DNS, getting undervoltage warning

Raspberry Pi 4, DietPi 7.5.2.

I’m setting up Pi-Hole on another Pi and accidentally typed in the wrong IP for this machine’s DNS, which I didn’t catch until I rebooted and it hung forever waiting for a network connection. I mounted the boot drive in a Raspberry OS VM and edited the DNS in /etc/resolv.conf back to I also set the wait for network time out back to 10 seconds and disabled network time sync in /boot/dietpi.txt. However, now when I boot I get an error saying I can’t log in as the default user (dietpi), so get logged in as root instead, but it’s immediately followed by an undervoltage warning and the keyboard is not responsive. I’m using the same power supply I’ve been using for the past 2 months, so I’m not sure what the issue is. Other power supplies have the same issue. Any thoughts?


usually incorrect DNS settings should not have any effect into under voltage messages. Can you have a look into kernel error messages

dmesg -l err,crit,alert,emerg

Right? That didn’t make sense to me. It seemed like weird timing though. I ended up wiping and installing a clean image because I couldn’t get the keyboard working at all.

After the wipe it gave me one undervolatge message when I booted it up and had it connected to an HDMI monitor. I don’t get that warning logging in via ssh though.

Here’s the output for dmesg -l err,crit,alert,emerg

[    1.987464] sd 0:0:0:0: [sdb] No Caching mode page found
[    2.012030] sd 0:0:0:0: [sdb] Assuming drive cache: write through
[    2.690983] sd 2:0:0:0: [sdc] No Caching mode page found
[    2.691000] sd 2:0:0:0: [sdc] Assuming drive cache: write through
[    3.039479] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip BCM4345/6
[    3.276429] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip BCM4345/6
[    3.276604] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip BCM4345/6
[    3.285415] brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM4345/6 wl0: Sep 18 2020 02:27:58 version 7.45.221 (3a6d3a0 CY) FWID 01-bbd9282b
[    4.927479] Under-voltage detected! (0x00050005)
[    5.403201] brcmfmac: brcmf_cfg80211_set_power_mgmt: power save disabled

I see have at least 2 disk attached to your device. Is this true? If yes, how are they powered? Via the SBC only or do they have an own power supply?

One is powered through the USB 2 port, the other has an external power supply.

running a HDD connected to the Pi without own power supply could easily lead to under voltage messages.

Let me quote our developer MichaIng

The RPi (and generally SBC’s) USB ports are not made to power anything from 2.5" or above. All four ports share an absolute maximum of 1.2A/6V, which is easily hit also by a single efficient SSD during peaks/startup

Ah, thank you. I’ll pull that one off and get a powered hub.

Let as know how it is going afterwards