What's the difference between factory.bin and sysupgrade.bin?

[BogMonster]

Digging my way around the delights of my bricked router learning new stuff, I came across something I don't understand.

There are factory.bin files, and sysupgrade.bin files, and I understand the general principle that you use the first one for initial installation and the second one for later upgrades, but what is the actual difference - and why do they need to be different?

Assuming you can connect to it, can you always flash a router with a factory.bin file as a "total reset" e.g. to downgrade from a later version - or why would you / why must you use one file rather than the other? What can you do with each one that you cannot do with the other?

Just trying to learn a bit for future use, and wondering why there is a difference. Thanks

[Lantis]

This is dependent on the specific router. In general the Factory image and the Sysupgrade image are the same, however the factory image has an additional header or extra partitioning scheme that allows the OEM upgrade function to recognise it as valid and allow the flash.

Once you have Gargoyle running this extra is not needed and can in some cases fail the flash due to unexpected extra data.

[BogMonster]

Ah right, thanks. My A7 was completely cabbaged when I started learning what TFTP was, so I guess the full version was the right one to choose - it worked anyway.

So if you have a Gargoyle image installed (say 1.14) and want to revert to an older one (e.g. 1.13) would you use the full, or can you "downgrade" with the upgrade file?

[Lantis]

Again generalising… always use the sysupgrade image once you are on Gargoyle regardless if up/downgrading

There are rare cases where between major versions there was a change that requires flashing factory again. The upgrade mechanism should tell you when that is needed, although it is much more robust in 1.15.