MergerFS + MC in bullseye: duplicate file system entries listing


I’ve been having this problem since upgrading to Bullseye. Researching shows that this is a know problem with the current bullseye mergerfs version 2.31 and mc version 4.8.26.
The suggested fix is to update mergerfs to ver. 2.32 (present in Debian testing). The thing is that I’m not able to do it, because an apt-secure, signature error.

W: GPG error: bookworm InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 9165938D90FDDD2E
E: The repository ' bookworm InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

I’m using Raspberry Pi 4, 8 GB, Dietpi 64bit version. A friend using Dietpi in a PC (AMD64 version) has done it without problem, following this

I’ve also tried this Problem installing package from testing repository (unmet dependencies / Breaks) - Raspberry Pi Forums, changing testing to bookworm, but the apt-secure problem apears.

Could you please help me to progress mergerfs to 2.32?

did you added bookworm manually to your configuration files? Because 64bit image (armv8) is using Debian repository and not the Raspbian one. Looks like Raspbian did not support Bookworm yet.

Anyway if you like to switch to Bookworm fully, you could do following

sed -i 's/bullseye/bookworm/g' /etc/apt/sources.list{,.d/*.list}
sed -i 's/bookworm/bullseye/g' /etc/apt/sources.list.d/raspi.list
apt update
apt upgrade
apt full-upgrade
. /boot/dietpi/func/dietpi-globals

Now, mergerfs 2.32.6-1 would be available

root@DietPi4:~# apt show mergerfs 
Package: mergerfs
Version: 2.32.6-1
Priority: optional
Section: utils
Maintainer: Ritesh Raj Sarraf <>
Installed-Size: 566 kB
Depends: libc6 (>= 2.28), libgcc-s1 (>= 3.0), libstdc++6 (>= 5.2), libfuse2, fuse
Download-Size: 229 kB
APT-Sources: bookworm/main arm64 Packages
Description: another FUSE union filesystem

Keep in mind you are moving to a Debian testing version and thinks might not work as expected.

As an alternative you add APT-Sources: bookworm and set preferences to avoid upgrading entire system

Thank you very much. I’ve taken the not-so-dangerous path.

First I’ve check mergerfs dependencies for bullseye and bookworm, and are exactly the same, so I don’t need to update any library. Then I did:

cd /etc/apt
mv sources.list.d sources.list.d.sos
cd /etc/apt/preferendes.d
mv raspi.pref raspi.pref.sos
cd /etc/apt
nano sources.list

then added deb Index of /debian bookworm main contrib non-free

apt update
apt install mergerfs

And then set all back. Removed bookwork sources.list line and

cd /etc/apt/preferendes.d
mv raspi.pref.sos raspi.pref
cd /etc/apt
mv sources.list.d.sos sources.list.d
apt update

And now it is working ok!

Hopefully apt will not try this downgrade packages sooner or later.

You could also keep the Bookworm list entry in addition to Bullseye and place a preferences file to allow only the mergerfs package to be installed from the Bookworm suite but nothing else.