Updating 3GS from 4.0 to 4.2.1

[esoin]

I have an unjailbroken 3GS at 4.0

I want to update firmware to 4.2.1 but iTunes gives me a "This device isn't eligible for the requested build" error.

I read it's because I don't have the proper SHSH backed up. I ran tiny umbrella and it only saved a 4.1 blob.

My ultimate goal is to use greenpois0n or PwnageTool to jailbreak 4.2.1, but I'm having trouble getting to 4.2.1.

Any thoughts? If I can't update to 4.2.1, is there a way to jailbreak my current firmware of 4.0?

Many Thanks!

[Simon]

Try again to see if it will save your 4.2.1 SHSH. Make sure you have the latest tiny umbrella.

[esoin]

Thanks

I updated TinyUmbrella and it saved an additional blob.

Saved SHSHs:
iPhone3GS 4.1 (8B117)
iPhone3GS 4.3 (8F190)

[Simon]

I would suggest just go to 4.1 then. Make a custom 4.1 with pwnage tool and restore to that. Not much difference between the two anyway.

Or just stay put on 4.0 until a 4.3 untethered jailbreak comes out.

[Freedom7]

@esoin After saving your current firmware to Cydia, I would recommend using Greenpois0n for your jailbreak.
http://greenpois0n.com/

In my experience it seems to be the most stable out of the current jailbreak tools available.

[Simon]

He doesnt have 4.2.1 SHSH though so greenpoison wont be of much help, unless he goes to 4.1 and uses a older version. Only problem with that though is that it would install a old version of cydia.