Restore vs. Recovery Mode vs. DFU Mode

[no0nefamous]

I'm looking for detailed descriptions of what actually happens when you use each recovery method, since Apple is not very transparent about this. I know the recommended reasons for each method, but I want to know all of what happens under the hood.


My understanding is:

Update OTA - a patch file is appled to your iOS installation, making only the modifications of the new version.

Update through iTunes/IPSW file - The entire iOS installation is replaced with the newest version or version you force selected.

Restore through iTunes/Finder - The phone is completely erased, the latest version of iOS is installed fresh.

Recovery Mode - A mode in which the phone can be force updated or restored if you are having issues updating or with something else, but otherwise is the same as performing a normal update or restore.

DFU Mode - The phone is completely erased and iBoot is re-installed, followed by the latest iOS version. If you weren't having issues with booting then the end result would be the same as a normal Restore process.


...But then I've seen other people claim that Recovery and DFU Mode give you a truly fresh installation that a regular restore does not. Which is it?

 

[an_apple.a.day]

Likely if you’re not receiving a reply from an apple software engineer you’re going to get hearsay. if in that regard you already knew what to expect from a rumors forum then the rhetorical response will find you after you’ve sifted through the fire and flames of what this thread will inevitably devolve to.

 

[Banglazed]

DFU aka Device Firmware Update allows device to be restored from any state which also support downgrading and bypass the iBoot bootloader. Happens when Boot ROM failed to load bootloader and can be used as a last resort. (Developer should know about this more than average user because of upgrading and downgrading to test iOS beta to troubleshoot software and hardware issue).

Recovery mode use iBoot bootloader and normally restore the device to factory setting with the latest signed iOS firmware. Bootloader normally does not support downgrading because it checks to make sure firmware is equal or higher than the current firmware.

I believe either mode will do a fresh installation. DFU mode is just a fail safe when recovery mode does not work and has better control over upgrading and downgrading bypassing bootloader requirement.

This guide states," A failure of the Boot ROM to load LLB [bootloader] (on older devices) or iBoot (on newer devices) results in the device entering DFU mode. In the case of a failure in LLB or iBoot to load or verify the next step, startup is halted and the device displays the connect to iTunes screen. This is known as recovery mode."

https://www.apple.com/ca/business-docs/iOS_Security_Guide.pdf

 

[no0nefamous]

I believe either mode will do a fresh installation.

So then is the regular Restore method also the same fresh installation, just with less steps? In other words, a Recovery or DFU Mode restore will not result in a "cleaner" install than a standard Restore?

 

[no0nefamous]

Okay. By digging through the iTunes Updater Logs (found in C:\Users\*YourName*\AppData\Roaming\Apple Computer\iTunes\iPhone Updater Logs) and comparing an iOS update through iTunes, a standard restore through iTunes, and a Recovery Mode restore, I believe I have found my answer.

The logs for a normal update and a standard iTunes restore are nearly identical aside from referring to some actions as either "update" or "erase". The log for a restore through Recovery Mode however is vastly different. I believe it is safe to assume that a standard restore erases your content and settings, but actually just "updates" your iOS installation with the latest one even if it's the same. It is possible to force iTunes to "Update" to the same IPSW build, after all. Meanwhile, a restore through Recovery Mode likely actually wipes everything and installs a truly "clean" installation.

I didn't feel like bothering with doing another restore through DFU mode, but I assume the same is true as with a Recovery Mode restore.

Of course, ultimately it probably doesn't matter much, but I feel better knowing that in the future if I have to do a restore, I know how to get the truly clean re-install.

 

[JM]

Okay. By digging through the iTunes Updater Logs (found in C:\Users\*YourName*\AppData\Roaming\Apple Computer\iTunes\iPhone Updater Logs) and comparing an iOS update through iTunes, a standard restore through iTunes, and a Recovery Mode restore, I believe I have found my answer.

The logs for a normal update and a standard iTunes restore are nearly identical aside from referring to some actions as either "update" or "erase". The log for a restore through Recovery Mode however is vastly different. I believe it is safe to assume that a standard restore erases your content and settings, but actually just "updates" your iOS installation with the latest one even if it's the same. It is possible to force iTunes to "Update" to the same IPSW build, after all. Meanwhile, a restore through Recovery Mode likely actually wipes everything and installs a truly "clean" installation.

I didn't feel like bothering with doing another restore through DFU mode, but I assume the same is true as with a Recovery Mode restore.

Of course, ultimately it probably doesn't matter much, but I feel better knowing that in the future if I have to do a restore, I know how to get the truly clean re-install.

Just to confirm I read you right: you did not read logs of DFU restore, but you think that doing a Recovery Mode restore makes a “vanilla” clean install?

Thanks

 

[no0nefamous]

Just to confirm I read you right: you did not read logs of DFU restore, but you think that doing a Recovery Mode restore makes a “vanilla” clean install?

Thanks

Correct. Or at least that is my assumption. The logs for a recovery mode restore are different from a standard restore. A standard restore looks very similar to an iTunes update log.

 

[Taz Mangus]

Just to confirm I read you right: you did not read logs of DFU restore, but you think that doing a Recovery Mode restore makes a “vanilla” clean install?

Thanks

I have done multiple Recovery Modes, both doing a Restore and Update. The Restore will download the latest version of iOS for your iPhone, erase the entire contents including any user data and install iOS. An update will also download the current iOS version but won’t erase all contents, but instead overwrite the iOS and not touch your user data.

 

[JM]

I have done multiple Recovery Modes, both doing a Restore and Update. The Restore will download the latest version of iOS for your iPhone, erase the entire contents including any user data and install iOS. An update will also download the current iOS version but won’t erase all contents, but instead overwrite the iOS and not touch your user data.

Thanks boss. I did a DFU new restore (no backup restore) and I gotta say, other than the huge battery drain from the indexing going on (I had no idea! It’s a REAL THING!) the battery life is appropriate, and I don’t have any weird glitches happening.

(Jury is still out on podcast resetting it’s settings every few days, though)

I’m also really enjoying the bare bones basic iOS, where I don’t have a bunch of apps on standby not being used. Only the essentials on my phone, and pretty much all the standard Apple settings on.

Not bad!

 

[jav6454]

DFU mode is like sandpaper to wood when it comes to eliminating software issues.

Got issues? This is the one I always recommend.

 

[JM]

DFU mode is like sandpaper to wood when it comes to eliminating software issues.

Got issues? This is the one I always recommend.

Whole heartedly recommend after the last few days after a DFU restore new. 👍 scared at first, but afterwards no problem.

 

[jav6454]

Whole heartedly recommend after the last few days after a DFU restore new. 👍 scared at first, but afterwards no problem.

During a botched jailbreak procedure, DFU was the life saver for several people.