Singularity sandbox on NAS

We have several machines that we want to run the same Singularity container on. As we already have a NAS mounted by every machine, we thought this would be a good place to store it without the need to think about distribution. Initially, we put a read-only container to test it, which was successful. We then needed to install additional system packages inside the container. Thus, we build a new sandbox container directly on the NAS (we have root permission on the NAS). However, we were not able to install packages in the sandbox (the singularity shell was started with the write flag

-w

and root permissions) and got the following error. E.g., from starting

update

inside the sandbox: error: cannot get shared lock on /var/lib/rpm/Packages error: cannot open Packages index using db5 - Operation not permitted (1) error: cannot open Packages database in /var/lib/rpm Error: Error: rpmdb open failed When we build the sandbox container locally on one of the machines and access it, we can install software through the package manager. To setup we do these commands. The first builds the sandbox from the library of images. In this case AlmaLinux 8 (we also tried it with CentOS 7, but it has the same problem). Then we enter the sandbox in shell mode to install packages. singularity build --sandbox al8.6-sandbox library://library/default/almalinux:8 singularity shell -w -B /mnt:/mnt al8.6-sandbox What can be the cause for the error on the NAS?