I unplugged my RPi (RPi#1) and moved it to another power outlet, and plugged it back in. RPi#1 is the brains of my distributed setup, containing the database and biggest SD card. All of the data my other RPIs collect are transferred to this one.

After plugging it back in, none of my other RPis were able to communicate with it. I was unable to SSH into it. I noticed the light on the usb-wifi dongle was not activated. I plugged an ethernet cable into it but was again unable to SSH into it and none of the other Pis could contact it.

I plugged the Pi into a monitor and received a few messages of high concern:

EXT4-fs (mmbclk0p2): unable to read superblock

No file system could mount root, tried: ext4
Kernel panic - noy syncing: VFS: Unable to mount root fs on unkown-block(172,2)

PANIC: VFS: Unable to mount root fs on unknown-block(179,2)

Entering kdb (current=0xcd828c80, pid1) due to Keyboard Entry

It was just working right before I unplugged it.

What does this problem even mean? I cant seem to get a comprehensive answer from googling. Some answers suggest this is fixable, others suggest the SD card has been corrupted.

I am now in "kdb" mode. Is there anything I can do to get out of this?

I'm now in a crappy situation for two reasons:

1) I use the RPi to measure the temperature of my homebrew beer. It has data for over 30 batches of beer going back almost a year from now. Some of that data is stored on the cloud but not all of it.

2) I JUST BREWED a batch of beer and I moved this RPi in order to get closer to the new batch. Not only does the RPi monitor the temperature, but it also is connected to a PowerSwitch Tail II and a heating device which increases the heat of the beer when it gets too cold. Without this I'll have to resort to manual methods.

  • sounds like the file system on the card is corrupt, step one backup. Best way will be to make a block level copy with dd, but can just try and copy the files. ONce everything is safe then you can try fsck etc.
    – rob
    May 21, 2014 at 9:34

1 Answer 1


I recovered from this by just doing an fsck on the partition which I found using gparted. I had to do the fsck twice. The Rpi now boots. It would appear that SD card are a bit iffy about brutal power off like just unplugging the board.

  • What partition was that?
    – Bex
    Mar 28, 2015 at 14:27

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