If you do have an operating system on your mac and it is functioning then you can download
Softwareupdate -fetch-full-installer -full-installer-version 11.3.1. Downloading Mac OS X Installers from App Store “Purchases” If you had at one point in time purchased or downloaded a version of MacOS or Mac OS X from the Mac App Store, then you should be able to re-download it from the Mac App Store by going go the “Purchases” section. Download Apple Mac OS X El Capitan for Mac to oS X El Capitan features new options for managing windows, smarter Spotlight search, app enhancements, and faster performance.
El Capitan using this method.
Go to Download OS and click on OS X El Capitan 10.11
this downloads InstallMacOSX.dmg to your Downloads folder.
The next section can only be done on a mac that is capable of running El Capitan.
This includes macs that have the potential to run El Capitan but have been upgraded to a newer OS.
A mac that came preinstalled with an OS later than El Capitan will refuse to do the next bit.
When downloaded open to InstallMacOSX.pkg, double-click on
Download El Capitan Usb
that and an installation window will open, this does not install El Capitan
but converts the InstallMacOSX.pkg to the Install OS X El Capitan.app which
you will find in your Applications folder, it should be 6.2GBs in size.
(If the installation window asks which disk you want to install to, you must pick
the disk that you are booted to at the time. Not any internal or external disk that
you want to eventually install El Capitan on, that is for later.)
To start the installation of El Capitan double click on the Install OS X El Capitan.app.
The copy of the install app self deletes after installing El Capitan, so make sure you keep a copy of the
InstallMacOSX.dmg if you need it in future, or you could just make a copy of the Install OS X El Capitan.app
prior to installing and moving it to an external drive for safe keeping.
It is also possible to create a bootable USB installer disk using the Install OS X El Capitan.app in the Applications
folder and the createinstallmedia command in the Terminal app.
Apple Download El Capitan Installer
Read the instructions here,
Download El Capitan Installer App Store
Aug 12, 2021 1:26 AM