Re: Disk capacity unchanged after deleting 21 GB MacPorts

[list_email--- via macports-users]

> On Nov 26, 2024, at 1:59 PM, list_email--- via macports-users 
> <macports-users@lists.macports.org> wrote:
> 
> 
> 
>> On Nov 26, 2024, at 1:55 PM, Jim DeLaHunt <list+macports-us...@jdlh.com> 
>> wrote:
>> 
>> Jerry:
>> 
>> On 2024-11-26 12:03, list_email--- via macports-users wrote:
>>> As a first step in re-installing MacPorts (long story), I ran
>>> $ sudo port -fp uninstall installed
>>> ...Before uninstalling, the Finder indicated that /opt/local contained 21 
>>> GB. After, /opt/local was nearly empty, as expected. I completed the steps 
>>> indicated to complete the uninstallation.
>>> I happened to check the “Used” quantity, as indicated by Finder on Get Info 
>>> on my boot volume (which contained /opt/local) before uninstalling, and 
>>> again after uninstalling. I expected to see this quantity reduced by 21 GB. 
>>> But there was no change!
>>> Why was the “Used” number unchanged after deleting 21 GB?
>> 
>> I am not an expert and don't have a definitive answer. But my first guess 
>> is: the APFS file system, and snapshots.  If something made a snapshot of 
>> the file system contents before you deleted everything in /opt/local, then 
>> maybe those file system contents are still present and occupying space in 
>> the snapshot.  Time Machine is one system which can create snapshots; there 
>> are probably others. And, you should ask yourself the question, what exactly 
>> is Finder's formula for its "Used" quantity?
>> 
>> Howard Oakley's excellent Eclectic Light Company blog has a steady stream of 
>> interesting details on the behaviour of Macs and macOS. The post, 
>> "Explainer: Disk free space" from 2021-12-04 
>> <https://eclecticlight.co/2021/12/04/explainer-disk-free-space/> may answer 
>> your question. There might be more insight in the blog posts tagged with 
>> "free space" <https://eclecticlight.co/tag/free-space/>.
>> 
>> TL;DR: File systems aren't as simple as they used to be.
>> 
>> I hope this is helpful,
>>    --Jim DeLaHunt
>> 
> Thanks, Jim, especially since this isn’t a MacPorts problem.
> 
> I’ll check out your links.
> 
> Jerry
> 
Jim,

That’s a really interesting blog. I now recall seeing it when I was trying to 
figure out why I couldn’t boot from a SuperDuper! backup when I got a new 
computer a couple years ago. Things really aren’t as simple as they once were.

Jerry