- My former system (one 1 week ago): Lubuntu 22.04.5 – LTS – x64 – fully updated
- My current system: Lubuntu 24.04.1 – LTS – x64 – fully updated
Lately I moved some files in PCManFM-Qt from my internal data drive (NTFS) to an external drive (ZFS). Luckily I noticed, that those files had not been moved
. . . but deleted. There was no warning or whatsoever. Those files also didn’t end up in the trash or something. They were simply gone.
I checked both drives and the zfs pool and the hardware for any issues. All fine. 
Since the new LTS release was already out for several months, I did blame it on my “old” Lubuntu 22 and decided to begin a fresh install of Lubuntu 24. While trying to save my “home” user profile, I recognized the system being quite unresponsive.
It was at this moment when my eyes stumbled upon the status bar of PCManFM-Qt:
"free space: 0 bytes"
Excuse me?!
After cleaning up the system drive the problem was solved . . . for now. The system ran fluidly and no more data loss on file movements.
Lubuntu was my first Linux experience by choice since Bionic Beaver 18.04 LTS (2018) and still I consider myself a Linux newbie. But . . . an unresponsive system and silent data loss? And no notification when the system lacks free disk space? 
That hit me really hard. As far as I know there are “low disk space” warnings on Ubuntu GNOME (“housekeeping”) - Microsoft Windows too, of course. I don’t know for all the other Linux Distributions or Apple’s stuff. Call me old-fashioned but a “low disk space” warning I consider being a mandatory stability feature. 
So I wanted to to ask if someone maybe could share a workaround, please?
There is a built-in daemon for “low battery” warnings, but I wasn’t able to find a hidden preference or a third-party application for low disk space notifications.
Any hint is appreciated. 
: Off topic (more or less) :
Since I had started preparations already, I finished switching to 24 LTS anyways.
By doing that I lost my entire Firefox profile (several hundred bookmarks collected over decades). By switching to snap edition of Firefox the Lubuntu developers changed the location of Firefox profiles. How could I possibly suspect this, since the old “.mozilla” folder was still existent in my home directory? When I noticed my bad luck, Lubuntu 24 was already up and unfortunately I had some partitions moved on the system drive, too. Perfect!
I had a tough time but I managed to recover all the bookmarks.
I also recovered the files that were deleted silently by PCManFM-Qt.
Despite the several hours of lost life time and the unpleasant adrenaline roller coaster, this entire odyssey did cost me a 170 € hard drive.
What a week! 
This was so far my worst Linux experience - just because a simple little warning notification is missing. So please may I express a spontaneous feature request at this point?
if ($free_space_sda1 < $free_space_user_specificed) ; then do
echo "$low_space_notification"
fi
Seriously. It saves hard drives.