Answering

I gave it some time from originally asking my question to see if there were any other solutions, but it looks like the solution I came up with while waiting is the only...

As you automount the disk, with default options, from fstab, the plugdev (or other) groups don't enter the picture. This is a standard mount. It is strange though,...

Here's the solution:

laptop-mode-tools is controlling power management for your hard drive, and you need to configure it appropriately for your situation.

Open...

In bash with extglob set you can use negative matching:

shopt -s extglob # often a default, could be already set
rm *.!(png)
rm !(*keep*|*save*) # everything except...