Sorry for top posting 

The 5% is just the default. I find it very wasteful on large capacity filesystems.

The good news is that it is adjustable, depending n what filesystem you are using, it can be even done live.

# tunefs -m2 /dev/sdx 

This will set the reserve to 2%.

Other filesystems will have different methods, and you are not limited to percentage, you can use -r to set the number of reserved blocks.

-Nick 

On Mon, Aug 25, 2025 at 14:33 CAREY SCHUG <sqrfolkdnc@comcast.net> wrote:
ok, for those that understand the internals, is that reasonable?
 
Could the system really need that much space in a hurry?
 
or maybe is 500mb enough even if the disk is larger? or some more complex formula, as in 100mb + 1% but no more than 5%?

Carey

On 08/25/2025 1:22 PM CDT Nick Accad <naccad@gmail.com> wrote:
 
 
 

On Mon, Aug 25, 2025 at 1:49 PM CAREY SCHUG via Talk <talk@lists.gtalug.org> wrote:
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.
 
By default, an ext filesystem will reserve 5% of its capacity.
 
So you are seeing 5% free + 5% reserved, comes out to the 10% you are looking for.
 
[snip]