sudo unshare -m bash -c "mount --make-rslave /home ; mount -n --make-rprivate -o bind /tmp/empty /home ; sudo -u $(whoami) firefox -ProfileManager -no-remote"

sudo unshare -m bash -c "mount --make-rslave /home ; mount -n --make-rprivate -o bind /tmp/empty /home ; sudo -u $(whoami) firefox -ProfileManager -no-remote" - creates an empty directory, - fork the mount table for the new bash process and its children (requires privileges), - unshare /home (required if / is mounted in shared mode [1]), - hide /home by mount-binding the empty directory, - start firefox in unprivilegied mode, without being able to access to user's files. [1] https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt https://www.kernel.org/doc/Documentation/filesystems/shareds...