[Q] How to return M8 to stock OS so that I can upgrade OTA? - AT&T HTC One (M8)

I got this device from AT&T last year. I went to htc-dev to unlock the bootloader, then I installed CyanogenMod. It hasn't been without problems but I have been relatively happy. However, to upgrade to the latest CM12, I need to update the bootloader. The most reliable way to do that is to return to stock and do the OTA.
I want to return my device to stock temporarily. I've looked through the forums and it seems like it should be possible. There are RUU available, but only for certain CIDs (not mine). The other option is to use a Nandroid backup. Apparently these are touchy. It's best to have your own (I don't), because you have to match the proper versioning or else you might have a brick. I went to check my phone information with
Code:
fastboot getvar all
and the result was strange compared to what I have seen elsewhere:
Code:
(bootloader) version: 0.5
(bootloader) version-bootloader: 3.16.0.0000
(bootloader) version-baseband: INVALID_VER_INFO
(bootloader) version-cpld: None
(bootloader) version-microp: None
(bootloader) version-main:
(bootloader) version-misc: PVT SHIP S-ON
(bootloader) serialno: [[B]redacted[/B]]
(bootloader) imei: [[B]redacted[/B]]
(bootloader) imei2: Not Support
(bootloader) meid: 00000000000000
(bootloader) product: m8_ul_ca
(bootloader) platform: hTCBmsm8974
(bootloader) modelid: 0P6B12000
(bootloader) cidnum: CWS__001
(bootloader) battery-status: good
(bootloader) battery-voltage: 0mV
(bootloader) partition-layout: Generic
(bootloader) security: on
(bootloader) build-mode: SHIP
(bootloader) boot-mode: FASTBOOT
(bootloader) commitno-bootloader: c3d94491
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0
all: Done!
finished. total time: 0.006s
The all-important "version-main" is missing, and the baseband-version is marked invalid. I'm not really sure where to go from here. I really want to update the bootloader so that I can get the next CyanogenMod build. (It fails to install with a complaint about the bootloader version. It wants 3.18 or 3.19, while I have 3.16.
I don't really know where to go or what to do now. Advice?
(Finally, I have a custom recovery [Team Win]. My phone is currently S-On)

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justine_d said:
There are RUU available, but only for certain CIDs (not mine).
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Click to collapse
Not sure where you've been looking, or why you think that. But RUUs are readily available for the AT&T version for every software version since release. And one of the few M8 versions that has consistently had RUUs. AT&T RUUs are listed on my Index tread, sticky at the top of the General AT&T forum section: http://forum.xda-developers.com/showthread.php?t=2751432
justine_d said:
The all-important "version-main" is missing, and the baseband-version is marked invalid. I'm not really sure where to go from here.
Click to expand...
Click to collapse
Your hboot number corresponds to software 1.xx, but it might be 1.12 (less common) or 1.58 (probably).
Restoring to stock using a nandroid is an option, but IMO more complicated than RUU. You will need to restore the stock nandroid, stock recovery, then OTA twice (to software 3.x then 4.x) in order to make your firmware (including hboot) current. Then flash TWRP and flash CM12.
For the RUU route, you will need to relock the bootloader, RUU, then unlock the bootloader (go through the HTCDev.com process) again. Then flash TWRP and CM12. But the downside to RUU is that it will wipe the phone, but that might not be much of an issue if you are a ROM flasher.

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redpoint73 said:
Not sure where you've been looking, or why you think that. But RUUs are readily available for the AT&T version for every software version since release. And one of the few M8 versions that has consistently had RUUs. AT&T RUUs are listed on my Index tread, sticky at the top of the General AT&T forum section: http://forum.xda-developers.com/showthread.php?t=2751432
Click to expand...
Click to collapse
Oh, I must have been looking in the wrong place. Somehow I found myself on the other (non-AT&T specific) index.
Your hboot number corresponds to software 1.xx, but it might be 1.12 (less common) or 1.58 (probably).
<snip>
For the RUU route, you will need to relock the bootloader, RUU, then unlock the bootloader (go through the HTCDev.com process) again. Then flash TWRP and CM12. But the downside to RUU is that it will wipe the phone, but that might not be much of an issue if you are a ROM flasher.
Click to expand...
Click to collapse
Wiping the phone is not an issue for me.. So then, I just pick one (I'm leaning toward 1.58 bootable RUU) and flash it, and that's it. I think I can figure it out. Does it matter which one I pick? Anything else I should know?
Thank you!

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Just checking in to say that everything worked perfectly, I am in the process of taking OTA updates now.

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justine_d said:
Wiping the phone is not an issue for me.. So then, I just pick one (I'm leaning toward 1.58 bootable RUU) and flash it, and that's it. I think I can figure it out. Does it matter which one I pick?
Click to expand...
Click to collapse
I know you've already got it sorted out. But just for your info:
The only restriction on RUUs (in addition to the fact that they need to match your phone's CID and MID) is that with s-on, you cannot run an RUU that is an earlier version than is on the phone (hboot, OS number), meaning you cannot "downgrade". Seeing as you had either version 1.12 or (probably) 1.58; and the only 1.x version RUU released was 1.58, any AT&T RUU would work in your case.
This also means that any equal or greater version AT&T RUU will work. Meaning with RUUs you can even have just skipped up to the latest Lollipop RUU (software 4.28) without running any "intermediate" RUUs or OTA updating up to LP. I would have pointed this out earlier, but I wasn't sure which method (RUU versus OTA) you preferred to use.
RUUs are in contrast to OTAs, which normally need to be installed in sequence.

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Thanks for clearing that up. There was definitely some underlying confusion on my part. In essence, there was no reason to flash the earliest RUU and then install the OTAs, when instead I could have flashed the latest RUU and achieved an equivalent result. Oh well, no harm (and I learned something).
I wish phones were as simple as PCs. Or rather, that phones were as difficult to screw up as PCs.
As an aside, do you have any personal favorite OS to flash to the M8?

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justine_d said:
Oh well, no harm (and I learned something).
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Click to collapse
Very true. And in regards to doing OTAs or RUUs, you now know how to do both!
justine_d said:
As an aside, do you have any personal favorite OS to flash to the M8?
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That's always a tough one. Its so personal. Some folks like AOSP or GPE, while some prefer Sense. Folks are looking for different features (customization, performance, etc.).
Personally, I'm not an AOSP/GPE person at all, and actually like Sense. And tend towards pretty stock ROMs, with maybe a few added customizations and performance tweaks, but otherwise pretty clean ROMs. I was on the stock Dev Edition Sense ROM for a while, than more recently SkyDragon Sense (so I could use Sense 7) and then LeeDroid.
That probably doesn't help you much , as it appears you may be more of an AOSP fan. You might check out the GPE ROMs, if you haven't already. IGPE is closer to stock Android than Sense, but should be more stable and bug-free than CM12, since its based on official HTC software.

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redpoint73 said:
Very true. And in regards to doing OTAs or RUUs, you now know how to do both!
That's always a tough one. Its so personal. Some folks like AOSP or GPE, while some prefer Sense. Folks are looking for different features (customization, performance, etc.).
Personally, I'm not an AOSP/GPE person at all, and actually like Sense. And tend towards pretty stock ROMs, with maybe a few added customizations and performance tweaks, but otherwise pretty clean ROMs. I was on the stock Dev Edition Sense ROM for a while, than more recently SkyDragon Sense (so I could use Sense 7) and then LeeDroid.
That probably doesn't help you much , as it appears you may be more of an AOSP fan. You might check out the GPE ROMs, if you haven't already. IGPE is closer to stock Android than Sense, but should be more stable and bug-free than CM12, since its based on official HTC software.
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Thanks for your input after I thought I was done, I managed to break it, fix it, break it again, and so on. I ran into a problem with receiving calls on CyanogenMod so I flashed back to Sense. I decided to shell $2.5 x 10**1 out for Sunshine S-OFF so that I could restore to any software with the RUUs. Then I just kept chasing the rabbit down the hole: SuperCID and Dev Edition. Then I tried a highly modded ROM (Viper One) to see what it had to offer. Finally I flashed back to CynogenMod because I've used it so long it feels most like home. The incoming call problem is absent in the Dev Edition radio firmware (but I've had to contend with other bugs in the past, only steady use will tell if things have gotten better or worse).
I definitely prefer the more stock feeling. The HTC Dev Edition Sense ROM was by far my favorite over either Viper One or the bloated AT&T stock software. I haven't tried any other AOSP based OS. The first time around I was content to HTCDev unlock and flash CM. I didn't even wait a week; I picked this device because I knew it was unlockable.

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justine_d said:
Finally I flashed back to CynogenMod because I've used it so long it feels most like home. The incoming call problem is absent in the Dev Edition radio firmware (but I've had to contend with other bugs in the past, only steady use will tell if things have gotten better or worse).
I definitely prefer the more stock feeling. The HTC Dev Edition Sense ROM was by far my favorite over either Viper One or the bloated AT&T stock software. I haven't tried any other AOSP based OS.
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Click to collapse
Then you really should check out the stock Google Play Edition (GPE) ROM or a custom GPE based ROM. GPE is supposed to be a AOSP type experience, no Sense and basically like a Nexus ROM. But its official HTC software, so should be pretty bug-free in comparison to CM12. Not to knock CM12 (I love it on my Samsung Tab Pro 8.4), but I know its had its share of bugs on the M8 (at least from my understanding).