Disk capacity unchanged after deleting 21 GB MacPorts

[list_email at icloud.com]

> On Nov 26, 2024, at 1:55 PM, Jim DeLaHunt <list+macports-users at 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