9. Disk Utility
Verify capacity, check SMART, run First Aid, and erase — fills the HD and OS Reset columns.
Open it from the macOS Utilities window — not the Utilities menu, that's where Terminal lives.
First: View → Show All Devices
This is off by default and it matters
Disk Utility defaults to Show Only Volumes, which hides the physical disk and shows only the mounted volumes inside it. That's why capacity often looks wrong — a volume in an APFS container reports the container's shared free space, not the drive's size.
Turn on View → Show All Devices before reading anything. The sidebar then nests correctly:
APPLE SSD AP0512Z ← physical device: read capacity + SMART here
└─ Container disk1 ← APFS container
├─ Macintosh HD ← system volume
└─ Macintosh HD - Data ← user data volumeVerify Capacity (HD)
Select the physical device row — the top-level one with the SSD's model name. Read Capacity, and cross-check it against diskutil info disk0 from Step 6. Round up to the nearest standard size; see HD for the table.
Check SMART Status
The physical device row also shows S.M.A.R.T. status. Verified is healthy; Failing means refurb-or-parts only, and belongs in Functional Issues.
Run First Aid
Select the container, then each volume, and run First Aid on each. Run it bottom-up — volumes first, then the container, then the physical device. Errors it can't repair mean the volume needs erasing.
This is the fix to try when Step 5 found a Macintosh HD that exists but won't boot.
Erase (OS Reset)
Only after Step 8 comes back clean.
Erasing does not clear Activation Lock or DEP
A locked machine erased is still a locked machine, now with no OS on it.
Don't erase the whole physical disk on T2 or Apple Silicon
Select the Macintosh HD volume group and use Erase Volume Group. Erasing the physical
device on these machines destroys the container that holds recoveryOS, and recovering from that
needs internet Recovery or an Apple Configurator revive.
On pre-T2 Intel, erasing the physical device is safe. Use:
- Format: APFS (macOS 10.13+) or Mac OS Extended (Journaled) for older
- Scheme: GUID Partition Map — only offered when erasing the physical device
- Name:
Macintosh HD
Delete any leftover extra volumes or containers with the – button so the unit ships with one clean container. Then reinstall macOS from the macOS Utilities window and record OS Reset = Yes.