system flash list
Use these commands to display the firmware disk usage and partitions.
FortiMail boots from the currently active partition unless you connect to the local console, interrupt the boot loader, and select a different method.
Firmware software updates replace the image on the active partition, unless you use the method to install fallback FortiMail firmware on the inactive boot partition. Once the inactive partition has firmware installed, you can use a local console connection to reboot and, during the boot loader, switch which partition is currently active to boot from the other partition instead.
Syntax
diagnose system flash list
Example
System Time: 2026-06-18 16:24:52 EDT (Uptime: 5d 16h 40m) Partition Image TotalSize(KB) Used(KB) Use% Active 1 377093 139826 37% Yes 2 377093 139826 37% No Image build at Jun 12 2026 19:44:03 for b0622