I’m trying to sell a 2009 MacbookPro. It’s the model MacbookPro5.5 and Apple supports macOS El Capitan 10.11 as latest available version.

I’ve wiped all data from the installed SSD and had to boot from an external disk. Now I’ve got two problems:

Download: OS X El Capitan This downloads as a disk image named InstallMacOSX.dmg. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder.

1. Download: macOS Big Sur, macOS Catalina, macOS Mojave, or macOS High Sierra These download to your Applications folder as an app named Install macOS version name.If the installer opens after downloading, quit it without continuing installation.
2. This free download of El Capitan is a standalone Disk Image InstallESD DMG installer for Macintosh based desktops and servers. Mac OS X El Capitan 10.11.6 Overview Mac OS X El Capitan 10.11.6 was released in 2015, the basic purpose of this release is to provide better security, performance, and reliability features.
3. This is the Install DMG of OS X El Capitan, downloaded from Apple's website just before this upload. This is for archiving purposes, just in case Apple decides to remove the download, so people can still download this in the future. 2021-02-24 22:39:21. Internet Archive HTML5 Uploader 1.6.4.

1. I’ve only got a Mac with Big Sur and Apple Silicon. I cannot use the package installer from the download provided by Apple to create the installer App for El Capitan. However, I need access to the installer so that I’m able to use the createinstallmedia command.
2. The 2009 MacbookPro is already wiped and has only access to the recovery mode. You cannot execute the package installer in Recovery Mode to extract the media.

Luckily I’ve found this blog post from Chris Warrick who explained how to extract the installer App from the package:

1. Attach an external Disk which contains the downloaded pkg from Apple. You’ll need enough space on that Disk to extract the pkg and it needs to be writeable
2. Open the Terminal from inside the Recovery Mode
3. Go to the mounted volume
4. Extract the package:

Now we can try to create the install media from the installer app. Make sure you’ve attach another disk which can be overwritten by the installer. In this example its named „MyBlankUSBDrive“:

The InstallESD.dmg image is missing, which we’ll need to add to the right location:

Now we’ll have a valid installation medium which can be used to start the installer from. You can reboot from that disk and should be able to install El Capitan.

However, I’ve encountered another annoying issue which caused the installer to fail:

El Capitan App Store

El Capitan Installer cannot be verified

Oh great… On to the next commands you can try from the Terminal inside the Recovery OS:

1. installer -pkg /Volumes/Mac OS X Install DVD/Packages/OSInstall.mpkg -target /Volumes/'XXX' where XXX is the name of the disk you’re installing to.
2. Wait for the installation to say it’s complete. You will not see any sort of progress display.

El Capitan Installer App Download Windows

Great, you’ve got El Capitan installed! Apple had some issues with certificates and people found a way to either use the above commands for installation or you’ll have to tinker with your Macs time settings so that the signature is valid again. I would have expected that Apple resigned all installers so I wouldn’t have to use these commands at all but doesn’t look like they did.