MacOS disk images are helpful if you want to create a sub-file system with different case sensitivity options, or if you want to store large files in a Time-Machine-friendly way. I use a disk image to store my VMware files, because they are huge and receive relatively small changes when the VM runs. When wrapped in a sparse bundle image, Time Machine gets those changes served in much smaller portions, which conserves backup space.
However, to provide a seamless experience, those kinds of disk images should not need user management, so auto-mounting is needed. MacOS already supports auto-mounting, but only for device-backed file systems. This project adds support for disk image auto-mounting.
To use it, add mount_diskimage as an executable mount map to of /etc/auto_master similar
to this (path names will vary for you):
/System/Volumes/Data/images /var/root/mount_diskimage -hidefromfinder
Then run automount -c for changes to become effective. You can configure the disk images
to be automounted in the imageMounts variable right in the code. Sorry, no config file.
This work is licensed under the WTFPL, so you can do anything you want with it.