pfSense Boot Environments are a pfSense+ feature that allow the system to take snapshots of key filesystem areas. This enables the ability for the firewall to be rolled back to an earlier known good state if problems are encountered with an upgrade, configuration change, or other potentially problematic situation.
Because snapshots of prior system states are being kept on the disk, the the capacity of the ZFS dataset (the disk as a whole, shown in the Disks Dashboard Widget) appears to shrink or reduce in size.
The first time this was an issue for me, I noticed an SG-1100 (which comes with 10.6GB of eMMC storage) with a total of only 1.6GB disk space. Once I realized there was four different Boot Environments on the system, I knew what the issue was. Deleting the unnecessary BEs gave back several gigabytes of disk space.
NOTE: The GUI will show the Space of a BE. I've found it's not accurate. If I show the following BE from the CLI, it's actually using 781M of disk space.
| Name | Version | Created | Last Booted | Space |
|---|---|---|---|---|
| default_20260227095156 | 24.11 | 2025-06-01 15:12 | 2026-01-10 12:45 | 588K |
List BEs
bectl listList ZFS Snapshots
zfs list -t snapshot