Cannot create a bootable disk with Mountain Lion installer

The problem is the current version of the older macOS 10.7 to 10.8 installers is they have been repackaged into a .pkg file that must be run to extract & build the actual macOS Lion installer app and that requires using a working Mac compatible with Lion. I have not seen anyone being successful using any method of creating a bootable USB installer from these newer packaged installers for 10.7 or 10.8.

Unfortunately the various DMG archives found within these older installers (including 10.10 to 10.12) are not enough to make a bootable installer (unlike the later versions 10.13+ where the BaseSystem.dmg can be used to make a bootable recovery USB stick...to simulate recovery mode).

Some years ago when Apple changed the packaging of the older installers and allowed them to be downloaded from outside the App Store, I had found instructions for manually extracting & creating a bootable macOS 10.11 El Capitan USB installer. It was a lot of work (directions were not entirely clear), but it worked. However, a year or to later Apple changed the packaging slightly where those directions no longer worked, although a slight modification would allow one to be created although it was not identical to the official method (or even the older method)...the OS install was a bit different). I only went through it because I did not have a compatible Mac at the time to use & only had a Linux system or newer incompatible Mac. I never tried it with the 10.7 or 10.8 installers, although I think they were a bit different anyway at the time.

I don't think the BaseSystem.dmg is enough on those older installers to even allow it to simulate recovery mode and even if it does, then you still need to contend with Apple's mostly broken nature of Recovery Mode for those older systems & installers. I guess you can try using Disk Utility to Restore the BaseSystem.dmg file to a USB stick. I don't recall if the USB stick had to be MBR or GUID, but I believe it needed MacOS Extended (Journaled) file system (only a requirement of Disk Utility since the Restore would wipe out the file system).

If your target Mac is compatible with OS X 10.6 Snow Leopard, then start by installing that from DVD. Then you can just upgrade normally to 10.7. It would actually be better to just stay on 10.6 if that Mac is compatible since macOS 10.7 Lion had a very bad vulnerability that was never patched....my organization forbid us to ever use Lion again (the only macOS that we were forbidden to use).

Otherwise you are going to have to do a lot of research & get very creative to make a bootable Lion USB installer.

Daniel Stonek wrote:

This iMac came with 10.6 Snow Leopard and was upgraded until 10.10 Yosemite. As far as I recall it was possible to upgrade to 10.11 El Capitan, the last possible upgrade.

Then why not create & use a bootable macOS 10.11 USB installer. You have a lot more options to find a compatible Mac with which to create a bootable 10.11 USB installer. Generally a Mac from 2007 to 2015 will work, but you can use the information in the following article to confirm a specific Mac is compatible with El Capitan since there aer some exceptions:

https://eshop.macsales.com/guides/Mac_OS_X_Compatibility

Anyway one have his Apple heart. Just in case some day I want to install a MacOS I'd like to have an installer.

Once you have access to compatible working Mac where you can extract the El Capitan installer & create a bootable USB stick, then you can create a dynamic writable DMG archive (do not compress it). Mount it and when you use the Terminal command to create the bootable USB installer, just point it to the mounted DMG.

Then with that custom DMG you can use any computer or OS (including Windows) to "burn" the bootable installer to a USB stick. I think that DMG would first need to be converted into a more standard raw archive, maybe an ISO. I was planning on making a User Tip for this procedure once I had time to test it out....I've actually been thinking of making some time during the holidays to do it. I know it works with macOS and I know it can be made to work with Linux (Linux has tools to read & mount DMG files).

This would allow you to keep a copy anywhere & include it in your backups. And any computer and OS can be used to make the physical bootable USB installer when a working compatible Mac is not available.

Some months ago, this year a Spanish guy uploaded a guide to Youtube on how to perform the new OS installation and to get an Mac OS installer in a flash drive.

This is the part where he downloads the same file as I did: https://youtu.be/vT88hO-KeTI?t=227

He succeed creating the installer in his flash drive!

Unfortunately I don't understand Spanish, but I wonder if it requires using DiskMaker X v3 on an older OS as well? He was definitely running it on an old OS.

Daniel Stonek wrote:

Early 2009 iMac 27" is compatible with El Capitan but there's no 10.11 installer available at Apple but from https://sourceforge.net/projects/os-x-el-capitan/ (6.2GB)

Here is an Apple article with instructions & links to download macOS installers from 10.7 to the current 15.x (except for 10.9 Mavericks):

How to download and install macOS - Apple Support

Try this:

Copy the following file out: Install OS X Mountain Lion.app > Contents > Shared Support > InstallESD.dmg.

Open Disk Utility and select the Flash Drive device name (not its volume or partition). Select the Erase tab on the right and then set format to Mac OS Extended (Journaled) and GUID Partition Map.

Select the Flash Drive volume (not the device), select the Restore tab at the top and then select the InstallESD.dmg. Click Restore and wait for the restoration to finish.

To make a bootable Mountain Lion USB stick you will need Diskmaker X 3 (at least) and since it has been well over a decade since I last used it, I cannot remember if Diskmaker X v5 can also build a Mountain Lion USB.

Daniel Stonek wrote:

Not that easy to get InstallESD.dmg From Terminal

AFAIR it is possible just to ctrl-click the installer.app in the Finder and copy the InstallESD.dmg to the Desktop for further processing. But it has been a while since I tried that. There is a much longer workflow to do the same thing and I can dig it, if needed. But maybe Apple has somehow screwed also that old installer somehow...

Where did you download the installer? AFAIR Mountain Lion had to be purchased from App Store, right? How large is it (not that I remember how large it should be)? Did you open the installer package right after downloading it and BEFORE any installation as the download may be deleted following install (I don't know if individual components might be deleted automatically, though).

As HWTech ninja'd apparently Apple has changed the installer since I last used it so the old info does not apply anymore.

Matti Haveri wrote:

Where did you download the installer? AFAIR Mountain Lion had to be purchased from App Store, right?

FYI, a few years ago Apple released the older full macOS installers for 10.7, 10.8 in DMG format outside of the App Store. The macOS 10.10, 10.11, and 10.12 full installers had been available in that form for some time before that. Those DMG archives contain a .pkg file which extracts the various components & builds the "Install macOS" installer app that traditionally appeared in the Applications folder.