macOS processes › Core system
What is diskimagesiod on Mac?
diskimagesiod handles reading and writing disk images, such as the .dmg files many apps come in. It runs while a disk image is open or being checked.
What it does
When you open a .dmg, macOS may verify it and then mounts it like a drive. diskimagesiod does the actual reading and writing for that image. It also handles other image formats, including sparse bundles, which Time Machine uses for backups to network drives.
Why it gets busy
- Verifying a large downloaded .dmg before it opens.
- Copying files to or from a mounted disk image.
- A Time Machine backup to a network drive, which is stored as a disk image.
- Virtualization or developer tools that keep disk images mounted.
Why is diskimagesiod using so much CPU?
diskimagesiod works while a disk image is being verified, copied to, or used for a network backup. Eject images you don't need and let backups finish.
Is it safe to quit?
Quitting it while an image is in use can interrupt the copy or backup and leave the image damaged.
How to calm it down
- Let a .dmg finish verifying, and eject it once you've installed the app.
- Eject disk images you're not using from the Finder sidebar.
- If it's tied to a network backup, let Time Machine finish, or choose Skip This Backup from the Time Machine menu.
In SystemWatch
In the website edition of SystemWatch you can see which files a process has open, which shows exactly which disk image diskimagesiod is working on.
