Installer needs 12,2Gb , but won't install with 17Gb free?

[Schroinx]

My mac mini has a 120gb disk. Its divided into a windows and a macos partition, each of 60gb. The macos partition has only been used for updates of macos. No apps, not personal files, not even a log in to apple. It says 17gb is free but additional 12,5Gb is needed. The storage overview shows 23,8Gb available. Sys takes 21Gb and apps 12Gb (only the ones comming with the os is on it). Time machine is off.

Any ideas to get around this?

 

[Quackers]

I'm pretty sure Big Sur requires 35GB.

 

[Airsculpture]

Yep quackers is right. The file is 12, but the install requires much larger space to install.

 

[Schroinx]

Thanks.

 

[Schroinx]

I solved it by cleaning windows (it has the function macos lacks with discarting old files) and resize the partition, to move the free space to the mac part so I got the 36 gb free. Afterwards it uses about 25gb, so I have moved the free space back to the windows partition.

 

[Furka]

I'm pretty sure Big Sur requires 35GB.

I think that is the cause for low boot speed on a Fusion drive with the SSD of 27Gb. It's my case.

 

[SmOgER]

To install it you need much more disk storage than it actually takes. The reason being that you need the original installer which takes almost as much as the whole OS and then more than that to extract (install) all the files and replace the old ones. Hence after installation you recover quite a bit of storage back.

FYI to reduce the space needed you can save installer on external storage.