I have a 1TB backup disk with an ext4 partition on it where I keep disk images of my two disks - one is 500GB/466GiB (my main disk) and the other is 400GiB (data partition from my second disk). I use the GNOME Disks app for creating these images.
After I deleted the 400GiB image from the backup disk I can't make a new backup image because there is not enough space left! I didn't send it to trash or something, I used
rm to delete the file.
df shows that there is only 52G available:
df . -h Filesystem Size Used Avail Use% Mounted on /dev/sdd1 917G 866G 52G 95% /media/szx/backup
ls gives only two files and
ls -a . . .. lost+found msres.img sda.img
du says that only 467GiB is used:
sudo du . -h 16K ./lost+found 467G .
Where did the remaining 932 - 467 = 465 GiB go?
I have disabled journaling and reduced reserved space to 0% using
tune2fs for the backup partition to get as much free space as possible. It did free up some space but not all of it.