Taking a closer look, I discovered two bugs in macOS’s “diskimages-helper” service that lead to this result. Thankfully, I was just running some tests and the file that disappeared was just test data. If you’ve ever lost data, you know the kick-in-the-gut feeling that would have ensued. When I unmounted and remounted the disk image, however, the video was corrupted. The whole file copied without error! I opened the file, verified that the video played back start to finish, checksummed the file – as far as I could tell, the file was intact and whole on the disk image. Curious, I copied a video file to the disk image volume to see what would happen. Bombich is the creator of Carbon Copy Cloner, which means Bombich is experienced with the use of the images.Įarlier this week I noticed that an APFS-formatted sparsebundle disk image volume showed ample free space, despite that the underlying disk was completely full. Sparse disk images are often used in backing up and cloning disks. In a blog post last Thursday, software developer Mike Bombich explained that he had uncovered the data writing flaw in the Apple File System, or APFS, through his regular work with “sparse” disk images.Ī “sparse disk image” is a file that macOS mounts on the desktop, and treats as if it were an attached disk drive. Software developer Mike Bombich has discovered a flaw in macOS High Sierra’s APFS file system that can lead to data loss when writing disk images.
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