Hi, I'd like to add here that I just ran into this in a different way. I do my development in profile=destkop chroots which are also missing the /dev/shm line in fstat like the default profile.
In my case upstream was using faketime(1) to tame some unreproducibility, but this needs access to /dev/shm to function at all. Curiously the permissions of /dev/shm were such that only root could write there: (unstable-amd64-dekstop):~$ ls -ld /dev/shm drwxr-xr-x 2 root root 40 Oct 16 10:36 /dev/shm Adding the fstab line fixes this as tmpfs seems to set the mount point to mode 777. FYI: I build my sbuild and "desktop" chroots with sbuild-createchroot(8). --Daniel