Technical Tip: Understanding differences between revision-image-auto-backup feature and normal upgrade
Description
This article explains how the 'revision-image-auto-backup' feature differs from the default firmware partition behavior on FortiGate devices, and how it can improve rollback strategies during firmware upgrades.
Scope
FortiGate.
Solution
FortiGate devices maintain two firmware partitions by default:
Primary partition.
Secondary partition.
During a standard firmware upgrade:
The new firmware image is written to the secondary partition.
The upgraded firmware becomes active after reboot.
The previous firmware version remains stored in the alternate partition.
This default mechanism already provides a rollback option to the immediately previous firmware version.
Default firmware upgrade behavior:
Example:
The current version is v7.0.12. The upgrade is performed to v7.2.5.
After the upgrade:
Active Partition | Backup Partition |
|---|---|
v7.2.5 | v7.0.12 |
If a rollback is required, FortiGate can boot using the previous firmware stored in the alternate partition. However, during multiple upgrade jumps, older firmware images are overwritten.
Example upgrade path: v7.0.12 -> v7.2.5 -> v7.2.8 -> v7.4.1.
Final result:
Active Partition | Backup Partition |
|---|---|
v7.4.1 | v7.2.8 |
In this scenario, v7.0.12 and v7.2.5 are no longer available because only two firmware partitions exist.
What revision-image-auto-backup does:
The 'revision-image-auto-backup' feature enhances the default rollback capability by saving additional firmware revision images during upgrades.
When enabled:
config system global
set revision-image-auto-backup enable
end
FortiGate automatically saves the current firmware image before an upgrade operation.
If sufficient flash storage space is available, older firmware versions can be preserved even after multiple upgrade jumps. This provides additional rollback flexibility beyond the standard dual-partition behavior.
Difference between default behavior and revision-image-auto-backup.
Default behavior | revision-image-auto-backup |
|---|---|
Uses only primary and secondary firmware partitions. | Saves additional firmware revision images. |
Keeps only the immediately previous firmware version. | Preserves older firmware versions during multi-step upgrades. |
Older images are overwritten during successive upgrades. | Older images can remain available if storage permits. |
Basic rollback capability. | Enhanced rollback strategy. |
To validate the image available, execute the following command:
FortiGate-401F# execute revision list imageÂ
IDÂ TIMEÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ADMINÂ Â Â Â Â Â Â Â Â Â Â Â FIRMWARE VERSIONÂ Â Â Â Â Â Â Â Â Â COMMENT
2  2026-07-30 07:48:00   admin            V7.6.4-build3596-REL0     Automatic backup (upgrade)
3  2026-08-03 03:23:51   daemon_admin     V7.6.6-build3652-REL0     Automatic backup (upgrade)
4  2026-08-03 03:47:05   admin            V7.4.7-build2731-REL0     Automatic backup (upgrade)Â
Note that the image will not be seen with the command 'diagnose system flash list'.
FortiGate-401F# diagnose sys flash list
Partition Image                                    TotalSize(KB) Used(KB) Use% Active
1         FG4H1F-7.04-FW-build2731-250120                 253871   139996  55% Yes  Â
2         FG4H1F-7.06-FW-build3652-260127                 253871   145846  57% No   Â
3         EXDB-1.00000                                  28327040   475960   2% No   Â
Image was built at Jan 20 2025 18:31:06 for b2731
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