Ubuntu – /oldroot/ and why do I get umount failed on shutdown


I get an umount failed for oldroot on shutdown error.

I have used several disk tool mount/gpart/fdisk/df etc to search for the /oldroot and I believe it is never mounted and does not exist.

However, when I shutdown I get umount failed error for this disk. The error is not causing a problem and I read on the web that it is normal.

  1. What is oldroot and why does Ubuntu think it is mounted?

  2. Is this real failure or a "normal" shutdown error?

  3. I don't always get this error but cannot determine why it will shutdown sometimes without errors. Any ideas?

Finally, question 1 is the most important question to me and I cannot find the answer on the internet.

Configuration 18.10, encrypted disk, nothing special, just barebone laptop.

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