Modern Linux systems are more complex than that. E.g. if I plug in a USB drive and one of its partitions has permissions brw-rw---- 1 root disk 8, 2 Mar 14

Modern Linux systems are more complex than that. E.g. if I plug in a USB drive and one of its partitions has permissions brw-rw---- 1 root disk 8, 2 Mar 14 11:51 /dev/sda2 I can still mount it even though I am not root or in the disk group. Why? Because many Linux desktops/apps can use polkit to get elevated access if a set of policy rules allow them to do so. E.g. there is typically a policy for udisks that allows clients in active sessions to mount filesystems. Similarly, I can use fwupd to update the firmware of my machine without ever becoming root, but as a user I certainly don't have the device permissions to do it. So how? The system has a policy rule that says that every active, local user that is in the wheel group can run an update. The fwupd daemon that runs as root will then execute the update for the user.