Chapter in this post:
This is again a manual that I just had to collect myself in an English forum. The reason why I want to turn an .app into a .dmg file is as follows: If you try to copy a macOS installer to a friend over the Internet because he needs it for an old Mac, you have the problem that this is over Dropbox or FTP is not working properly. This is because an .app file on the Mac is actually not a single file, but a folder with many files it contains. The Finder only shows the folder as a file with the extension .app - provided that the file extensions have been shown.
If you copy an .app file into the Dropbox or via FTP to a server, it happens, for example, that Dropbox displays a file that is 0 KB in size. Virtually nothing has been loaded from the installer, just a faulty file that has no content.
On the other hand, on a server that is supplied with the installer file via FTP, one has the problem that a folder with a lot of content is displayed and the acquaintance cannot simply download a single file. So this path is not expedient either.
For the last few months I have always solved this problem by making a ZIP file from the macOS Installer.app. However, due to the size of the file, this takes a long time and I often got the feedback that the other person could not load the file completely because it was supposedly incomplete. But even if the transfer works: A macOS installer is around 5 to 10 GB and unzipping a file of this size is a real challenge for older Macs.
Only today did I get the idea to see if the Installer.app could not be turned into a .dmg file, because DMGs are used as the method of choice for almost all software downloads for Macs, if you Want to make apps available on the Internet.
If you want to spruce up the folder view of the DMG archive a bit, you can, for example, copy an alias of the programs folder so that users can put an app directly into the program folder.
For further options you can either use the gear symbol at the top of the folder's menu bar or the Finder menu "View".
The "Display options" window can be displayed using the gear symbol. With this you can set the font size, the folder background, the icon size and much more for the corresponding folder.
If you also want to hide the sidebar in the folder, click on the folder window and go to the "View" menu in the Finder and find the item "Hide sidebar" there. All things that you do with the folder are also backed up with the creation of the DMG file.
Creating the image took a good 2018 to 10 minutes even on my MacBook Pro 15, but opening the DMG archive takes seconds and hardly requires any computing power. In addition, the DMG files can easily be exchanged via cloud services such as Dropbox, OneDrive or have something similar exchanged. Even shipping with Droppy.ch, FileMail or wetransfer is not a problem if you do not exceed the maximum file size.
Jens has been running the blog since 2012. He appears as Sir Apfelot for his readers and helps them with problems of a technical nature. In his free time he drives electric unicycles, takes photos (preferably with his iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions for current bugs.