ok, part of my problem is not understancing how much linux lies to me.

 

after a reboot, it does show 95% full.

 

but doing the math on the blocks used/total,

 

it is technically under 90% full, and what it tells me is "available" is 5%, so the difference is being withheld from me.  unless those numbers are innacurate or there is some basic issue I don't understand.

 

I don't know enough of the internal workings to know if that is reasonable, or a holdover from when disks were smaller.

 

if it is more than reasonable, the problem is that I could get to ignore the "disk almost full" warnings even when it really is almost full.