Expand a VM disk

Increase a stopped Lume VM's disk and verify the guest capacity.

Use this guide to increase an existing VM's total disk capacity. Lume does not support shrinking VM disks.

Preview the resize#

Stop the VM and validate the proposed size without changing the disk:

lume stop macos-tahoe
lume set macos-tahoe --disk-size 120GB --dry-run

Resolve any reported layout, encryption, host-space, or VM-state error before continuing.

Expand the disk#

Set the new total capacity:

lume set macos-tahoe --disk-size 120GB

Lume creates a rollback copy for macOS VMs. The operation can take several minutes while Lume preserves RecoveryOS and expands the APFS container.

Use --keep-backup to retain the rollback files after success:

lume set macos-tahoe --disk-size 120GB --keep-backup

Use --no-backup only when you have another verified copy of the VM. Automatic rollback is unavailable when a resize without a backup fails.

Verify the guest capacity#

Boot the VM and inspect its root container:

lume run --no-display macos-tahoe
lume ssh macos-tahoe 'diskutil info / | grep "Container Total Space"'
lume stop macos-tahoe

For Linux VMs, grow the guest partition and filesystem after Lume increases the image. The exact commands depend on the partition table and filesystem.

See Disk resizing limits for supported macOS layouts. Read How Lume expands macOS disks for the RecoveryOS and rollback model.