Develop Bugs

[Q] Nexus 7 Newb would like feedback on plan for setting up my device

I recently picked up a Nexus 7, unlocked it, and loaded KitKat yesterday with the factory image. I have set the device up now and would like to use a custom backup to take an image of the 7 and then store that image off of the device on an external drive since I only have a 16gb 7.
I have downloaded Clockworkmod ROM Manager to do this. Is it easily feasible to make a stock image and then transfer the image to an external drive? I'm having an issue installing the Clockworkmod Recovery tool, but I posted a question about that in a different forum.
Any advice would be appreciated.
Thanks,
Rick

I presume you have a custom recovery installed in addition to the ClockWorkMod Manager? If not, use the WugFresh Nexus Root Toolkit to install that, then boot into the recovery and select the backup option. It will create a folder on the root of your device called clockworkmod which will contain your backups. Just copy that to your PC, and transfer it back to the device when you need it.

C5Longhorn said:
I recently picked up a Nexus 7, unlocked it, and loaded KitKat yesterday with the factory image. I have set the device up now and would like to use a custom backup to take an image of the 7 and then store that image off of the device on an external drive since I only have a 16gb 7.
I have downloaded Clockworkmod ROM Manager to do this. Is it easily feasible to make a stock image and then transfer the image to an external drive? I'm having an issue installing the Clockworkmod Recovery tool, but I posted a question about that in a different forum.
Any advice would be appreciated.
Thanks,
Rick
Click to expand...
Click to collapse
I've used ROM Manager a fair amount for creating backups. It works well, but like was said previously, you'll need to flash a custom recovery. The two main choices are Clockworkmod (CWM) and Team Win Recovery Project (TWRP). CWM works well with ROM Manager in my experience on another device.
I've found TWRP much easier to use though. It features a touch interface. You'll be able to customize the backup file name if you initiate a backup in recovery mode. The file name will also allow spaces, while CWM doesn't.
Check it out at teamw.in/project/twrp2. I think the recoveries are the same, but make sure you select the correct Nexus 7 model (LTE or Wi-Fi). You can flash the image in the bootloader using fastboot. Instructions are avalaible on the TWRP website.

Wrngway said:
I've used ROM Manager a fair amount for creating backups. It works well, but like was said previously, you'll need to flash a custom recovery. The two main choices are Clockworkmod (CWM) and Team Win Recovery Project (TWRP). CWM works well with ROM Manager in my experience on another device.
I've found TWRP much easier to use though. It features a touch interface. You'll be able to customize the backup file name if you initiate a backup in recovery mode. The file name will also allow spaces, while CWM doesn't.
Check it out at teamw.in/project/twrp2. I think the recoveries are the same, but make sure you select the correct Nexus 7 model (LTE or Wi-Fi). You can flash the image in the bootloader using fastboot. Instructions are avalaible on the TWRP website.
Click to expand...
Click to collapse
TWRP will also allow you to backup, restore, and flash from a USB drive if you get a USB OTG cable.
Sent from my SM-P600 using XDA Premium HD app

nrage23 said:
TWRP will also allow you to backup, restore, and flash from a USB drive if you get a USB OTG cable.
Sent from my SM-P600 using XDA Premium HD app
Click to expand...
Click to collapse
I don't think TWRP is working with 4.4 build number KRT16S
Can anyone confirm? I just tried to flash the latest TWRP recovery 2.6.3.1 and it was not working when I rebooted into recovery. I was still getting the stock image.
Rick

C5Longhorn said:
I don't think TWRP is working with 4.4 build number KRT16S
Can anyone confirm? I just tried to flash the latest TWRP recovery 2.6.3.1 and it was not working when I rebooted into recovery. I was still getting the stock image.
Rick
Click to expand...
Click to collapse
TWRP working fine here..

C5Longhorn said:
I don't think TWRP is working with 4.4 build number KRT16S
Can anyone confirm? I just tried to flash the latest TWRP recovery 2.6.3.1 and it was not working when I rebooted into recovery. I was still getting the stock image.
Rick
Click to expand...
Click to collapse
Just backed up stock KitKat to a thumb drive and flashed newest 4.4 Omni Rom from thumb Drive. Use the WugFresh Nexus Toolkit to flash recovery. It makes it much simpler.

C5Longhorn said:
I don't think TWRP is working with 4.4 build number KRT16S
Can anyone confirm? I just tried to flash the latest TWRP recovery 2.6.3.1 and it was not working when I rebooted into recovery. I was still getting the stock image.
Rick
Click to expand...
Click to collapse
From what I've read, the stock recovery for KRT16S is the same as KRT16O. I'm running the latest TWRP on KRT16O without issue.
Assuming your bootloader is unlocked, you shouldn't have an issue. Can you list the steps you're using to flash recovery? Maybe you're missing something.
If you have the correct driver on your computer and you're using fastboot, the command should be "fastboot flash recovery [insert recovery file name].img" from the fastboot directory.

Wrngway said:
From what I've read, the stock recovery for KRT16S is the same as KRT16O. I'm running the latest TWRP on KRT16O without issue.
Assuming your bootloader is unlocked, you shouldn't have an issue. Can you list the steps you're using to flash recovery? Maybe you're missing something.
If you have the correct driver on your computer and you're using fastboot, the command should be "fastboot flash recovery [insert recovery file name].img" from the fastboot directory.
Click to expand...
Click to collapse
Ok, maybe I was doing something wrong. The command line indicated it was installing correctly when I flashed it. However, when I rebooted to recovery it was never TWRP.
I just installed Clockworkmod Recovery so it was probably an error on my end.
Now, since I have made a backup, how can I identify where it is stored? I would like to move it to my computer since I only have a 16gb 7.
Thanks for all the replies,
Rick

I can't remember the default location. I think it's sdcard/clockworkmod/backups.
If you remember the file name, you can just search for that using ES File Explorer or a similar app.

Wrngway said:
I can't remember the default location. I think it's sdcard/clockworkmod/backups.
If you remember the file name, you can just search for that using ES File Explorer or a similar app.
Click to expand...
Click to collapse
great, thanks for all the help. I will probably reflash back to stock and then rebuild my device and backup. I have OCD about making sure I've got the cleanest install and right now don't know that for sure since it's been trial and error.

They are saved in /mnt/shell/emulated/clockworkmod/backup
They are hidden from other apps, so you need a file explorer with root to move them.

Great, thank you for the reply. The help from folks on the forum has been fantastic and really helps a newb.
Rick

Cannot Root. Need help!

I installed the KK ROM wit the TOT method and then rooted the phone and installed the CWM recovery as an apk. Now when I go into SU, it says I am not rooted. I tried 2 methods to root but unsuccessful. It boots into CWM recovery and then nothing. Do I need to reinstall the OS with the TOT method again? Any ideas?

HD2FORNICK said:
I installed the KK ROM wit the TOT method and then rooted the phone and installed the CWM recovery as an apk. Now when I go into SU, it says I am not rooted. I tried 2 methods to root but unsuccessful. It boots into CWM recovery and then nothing. Do I need to reinstall the OS with the TOT method again? Any ideas?
Click to expand...
Click to collapse
This method works perfectly: http://forum.xda-developers.com/showpost.php?p=51480568&postcount=1
After root, use this to get the correct recovery: http://forum.xda-developers.com/showpost.php?p=52945705&postcount=1
Once the phone boots into the UI, use Freegee to install the latest recovery.

jdk2 said:
This method works perfectly: http://forum.xda-developers.com/showpost.php?p=51480568&postcount=1
After root, use this to get the correct recovery: http://forum.xda-developers.com/showpost.php?p=52945705&postcount=1
Once the phone boots into the UI, use Freegee to install the latest recovery.
Click to expand...
Click to collapse
Tries and doesn't work. It goes back to my CWM recovery and does nothing. Thanks.

HD2FORNICK said:
Tries and doesn't work. It goes back to my CWM recovery and does nothing. Thanks.
Click to expand...
Click to collapse
flash the hacked twrp. that gets me out of cwm bootloop.

Same problem here phone was rooted and then installed CWM and for some reason lost root. Its not a CWM bootloop.
When the root step requires "Apply Update from ADB" I cannot because CWM doesn't have that option.

mk3 said:
Same problem here phone was rooted and then installed CWM and for some reason lost root. Its not a CWM bootloop.
When the root step requires "Apply Update from ADB" I cannot because CWM doesn't have that option.
Click to expand...
Click to collapse
I got bad news bro. I had to re TOT the phone and start from scratch. There is a CWM 6.0.4.4 floating around causing this issue. The phone loses root but it constantly boots into CWM when trying to root.

ROOT achieved, now need recovery!
OK, so I had to re TOT and get the phone back to factory state with 4.4. Then I was able to root successfully and now I am wondering how and which recovery to use. Could someone please post a link to Philz recovery and can I flash it with the same root toll with ADB sideload? THanks.

Ok I figured out how to get root back on my phone! Yay!
Run the same F240 root tool as usual, it will reboot phone into CWM recovery but you can't choose "apply update from ADB" so instead pick INSTALL ZIP, then choose INSTALL ZIP FROM SIDELOAD. Press any key on computer to load root files then at next step in CWM choose GO BACK, then choose REBOOT SYSTEM NOW. At next step in CWM will ask "Rom may flash stock recovery on boot. F1 This can not be undone." here I choose NO. Phone will reboot and root is restored. I think before I was scared and chose YES on this step and that's what lost my root.
Root Check Basic and SuperSU both show I am rooted and back to okay.
:good:

mk3 said:
Ok I figured out how to get root back on my phone! Yay!
Run the same F240 root tool as usual, it will reboot phone into CWM recovery but you can't choose "apply update from ADB" so instead pick INSTALL ZIP, then choose INSTALL ZIP FROM SIDELOAD. Press any key on computer to load root files then at next step in CWM choose GO BACK, then choose REBOOT SYSTEM NOW. At next step in CWM will ask "Rom may flash stock recovery on boot. F1 This can not be undone." here I choose NO. Phone will reboot and root is restored. I think before I was scared and chose YES on this step and that's what lost my root.
Root Check Basic and SuperSU both show I am rooted and back to okay.
:good:
Click to expand...
Click to collapse
Ok so i need a custom recovery such one did you use. I need one that can read the external card.

HD2FORNICK said:
Ok so i need a custom recovery such one did you use. I need one that can read the external card.
Click to expand...
Click to collapse
I used that CWM 6.0.4.4 recovery to install a custom recovery only. Once it flashes the recovery, reboot the phone. Answer No to the disclaimer in recovery and let the phone boot into kitkat. Then I used Freegee to install it's latest version of CWM. Ignore the warning if you get one in Freegee. It will install the newer recovery.

jdk2 said:
I used that CWM 6.0.4.4 recovery to install a custom recovery only. Once it flashes the recovery, reboot the phone. Answer No to the disclaimer in recovery and let the phone boot into kitkat. Then I used Freegee to install it's latest version of CWM. Ignore the warning if you get one in Freegee. It will install the newer recovery.
Click to expand...
Click to collapse
The last time I did that and installed the CWM 6.0.4.4 I lost root and freegee couldn't install another recovery but I'll give it a shot again.

HD2FORNICK said:
The last time I did that and installed the CWM 6.0.4.4 I lost root and freegee couldn't install another recovery but I'll give it a shot again.
Click to expand...
Click to collapse
You'll loose root if you answer "Yes" to the disclaimer CWM throws when you try to reboot. Just answer "No" and you won't loose root.

jdk2 said:
You'll loose root if you answer "Yes" to the disclaimer CWM throws when you try to reboot. Just answer "No" and you won't loose root.
Click to expand...
Click to collapse
Thanks bro. Worked!

jdk2 said:
I used that CWM 6.0.4.4 recovery to install a custom recovery only. Once it flashes the recovery, reboot the phone. Answer No to the disclaimer in recovery and let the phone boot into kitkat. Then I used Freegee to install it's latest version of CWM. Ignore the warning if you get one in Freegee. It will install the newer recovery.
Click to expand...
Click to collapse
Can you please share the custom recovery that you flashed from 6.0.4.4 ?
Sent from my LG-E988 using Tapatalk

Akhileshjj said:
Can you please share the custom recovery that you flashed from 6.0.4.4 ?
Sent from my LG-E988 using Tapatalk
Click to expand...
Click to collapse
It was CWM 6.0.4.7 and included with Freegee.

jdk2 said:
It was CWM 6.0.4.7 and included with Freegee.
Click to expand...
Click to collapse
Can you be bit more specific on how did you download the 6.0.4.7 from freegee. As i see only install option available only in freegee but not download so that it can be installed from 6.0.4.4..
Sent from my LG-E988 using Tapatalk

Akhileshjj said:
Can you be bit more specific on how did you download the 6.0.4.7 from freegee. As i see only install option available only in freegee but not download so that it can be installed from 6.0.4.4..
Sent from my LG-E988 using Tapatalk
Click to expand...
Click to collapse
When I opened Freegee, it presented the option to install 6.0.4.7. It wasn't a stand alone version but part of Freegee.

mk3 said:
Ok I figured out how to get root back on my phone! Yay!
Run the same F240 root tool as usual, it will reboot phone into CWM recovery but you can't choose "apply update from ADB" so instead pick INSTALL ZIP, then choose INSTALL ZIP FROM SIDELOAD. Press any key on computer to load root files then at next step in CWM choose GO BACK, then choose REBOOT SYSTEM NOW. At next step in CWM will ask "Rom may flash stock recovery on boot. F1 This can not be undone." here I choose NO. Phone will reboot and root is restored. I think before I was scared and chose YES on this step and that's what lost my root.
Root Check Basic and SuperSU both show I am rooted and back to okay.
:good:
Click to expand...
Click to collapse
Thanks its works

[Q] What to do now?

So I have to admit I am pretty overwhelmed but the amount of information. So I wanted to find out from the community what do I do now.
My RAZR my is rooted, boot loader unlocked and on stock KK 4.4.2. I have no idea how to get the customer recovery on my phone the forrest ways as I have seen it many different ways. SO how it it I get TWRP on my device now. Once I do, is that how I install a rom? Will that wipe the stock one?

Easiest way to flash TWRP is through an app called "Flashify," which is found on the Google Play store. Download the correct version (TWRP 2.7.1.0 works well on the KK build) in ZIP format. Save to your phone. Open Flashify, backup your current recovery, and choose the new TWRP to flash. Reboot and see the new recovery.
In the new recovery, perform a full backup, throw it on your computer for safe keeping. There are a select few ROMs that work on the 3.4 kernel that the KK build uses, so if you would like to be opened to all the other ROMs, find the 98.30.1 update and flash it using your favorite method. After you flash back to the update, reinstall TWRP if it is gone, and then have fun.
To flash a ROM, just throw the ZIP file on your phone for your ROM, boot into TWRP and choose to install, and select the file(s) to flash. This does wipe the stock one. Perform a nandroid backup to save it.

xKroniK13x said:
Easiest way to flash TWRP is through an app called "Flashify," which is found on the Google Play store. Download the correct version (TWRP 2.7.1.0 works well on the KK build) in ZIP format. Save to your phone. Open Flashify, backup your current recovery, and choose the new TWRP to flash. Reboot and see the new recovery.
In the new recovery, perform a full backup, throw it on your computer for safe keeping. There are a select few ROMs that work on the 3.4 kernel that the KK build uses, so if you would like to be opened to all the other ROMs, find the 98.30.1 update and flash it using your favorite method. After you flash back to the update, reinstall TWRP if it is gone, and then have fun.
To flash a ROM, just throw the ZIP file on your phone for your ROM, boot into TWRP and choose to install, and select the file(s) to flash. This does wipe the stock one. Perform a nandroid backup to save it.
Click to expand...
Click to collapse
Thanks for this, it makes things much clearer. I noticed in the flashify app that you can flash bot rims. DO I have to do that too? or is it just the recovery that I need to worry about?

nxion said:
Thanks for this, it makes things much clearer. I noticed in the flashify app that you can flash bot rims. DO I have to do that too? or is it just the recovery that I need to worry about?
Click to expand...
Click to collapse
I'm not sure what you're saying, but recovery is the important thing. Just flash ROMs through recovery. Read directions for each ROM before you do so as well. Most require wiping the System partition at the least, but it's best to do a factory reset (via TWRP) before an install. Backup your data with Titanium.

xKroniK13x said:
I'm not sure what you're saying, but recovery is the important thing. Just flash ROMs through recovery. Read directions for each ROM before you do so as well. Most require wiping the System partition at the least, but it's best to do a factory reset (via TWRP) before an install. Backup your data with Titanium.
Click to expand...
Click to collapse
Sorry, I was trying to say in Flasify, there is the option to flash a boot and recovery image. I was asking if I had to do both.

nxion said:
Sorry, I was trying to say in Flasify, there is the option to flash a boot and recovery image. I was asking if I had to do both.
Click to expand...
Click to collapse
Boot image, I believe, is just the logo your phone displays when you first turn it on (think: red M, or after you unlock, the bootloader warning). Just the recovery is the important part.

xKroniK13x said:
Boot image, I believe, is just the logo your phone displays when you first turn it on (think: red M, or after you unlock, the bootloader warning). Just the recovery is the important part.
Click to expand...
Click to collapse
Boot image is linux kernel, do not try to touch it.

Klen2 said:
Boot image is linux kernel, do not try to touch it.
Click to expand...
Click to collapse
Good to know lol. Thank you.

[Q] LS990 Certificate verify/secure boot error(s)

Hi there! I rooted my LS990 on lollipop 5.0.1 a recently and I tried to use TWRP to get a ROM on it and when I tried to install TWRP it came back with the error right after the LG logo on reboot when I tried to boot to recovery. I looked through a few threads but they all led to other LG models and not the LS990 from what I saw. I'm not able to boot to recovery, update my phone or factory reset. My endgame would be able to factory reset my phone and not worry about rooting it because it's just caused problems for me.
If there's any help I can get it would be much appreciated!

What method did you use to install TWRP? Try either TWRP Manager or Flashify from the Play Store, or push the recovery *img via adb shell or a terminal emulator app. You can find the latest *img file for the LS990 here...
https://twrp.me/devices/lgg3sprint.html
Follow the "dd Install Method (Requires Root):" directions at the bottom of the page. And make sure to never take an OTA update or perform a factory reset w/ a custom recovery like CWM or TWRP installed.

redduc900 said:
What method did you use to install TWRP? Try either TWRP Manager or Flashify from the Play Store, or push the recovery *img via adb shell or a terminal emulator app. You can find the latest *img file for the LS990 here...
Follow the "dd Install Method (Requires Root):" directions at the bottom of the page. And make sure to never take an OTA update or perform a factory reset w/ a custom recovery like CWM or TWRP installed.
Click to expand...
Click to collapse
I had downloaded TWRP from the Play Store and used the instructions in the app to patch my SD card and then downloaded the latest img from TWRP and when I tried to install the img it came back unsuccessful and since then I have had my error(s).

Try using the Flashify app instead. Make sure the external SD has indeed been patched by running the "SDFix: KitKat Writable MicroSD" app (available from the Play Store) beforehand. The app also works w/ Lollipop, and can be uninstalled after the verification or installation of the fix.

redduc900 said:
Try using the Flashify app instead. Make sure the external SD has indeed been patched by running the "SDFix: KitKat Writable MicroSD" app (available from the Play Store) beforehand. The app also works w/ Lollipop, and can be uninstalled after the verification or installation of the fix.
Click to expand...
Click to collapse
I'll give Flashify a shot. Just to be sure on what I do, I am flashing a new recovery img correct or am I doing a boot img?

Yes, a recovery image.

redduc900 said:
Yes, a recovery image.
Click to expand...
Click to collapse
Does it matter which one I do? There is a choice of TWRP, Philz and CMM.

TWRP is the recovery of choice for the G3.

redduc900 said:
TWRP is the recovery of choice for the G3.
Click to expand...
Click to collapse
It told me the flash was successful but when I rebooted my phone when it prompted me to it rebooted back to the certificate verify and secure boot error.

I forgot about the locked bootloader for that model. You'll need to first download the LS990 BUMP *.img file to your phone from here...
http://downloads.codefi.re/thecubed/lg_g3/bump/
... then open Flashify, select Recovery Image -> Choose a file -> Downloads, and select the TWRP recovery image you downloaded.

redduc900 said:
I forgot about the locked bootloader for that model. You'll need to first download the LS990 BUMP *.img file to your phone from here...
... then open Flashify, select Recovery Image -> Choose a file -> Downloads, and select the TWRP recovery image you downloaded.
Click to expand...
Click to collapse
Do I need to restore my old recovery before I do this or can I just go ahead and flash this new recovery?

No, just flash the new recovery image.

redduc900 said:
No, just flash the new recovery image.
Click to expand...
Click to collapse
Okay, I flashed the signed img from that download and it still giving the the boot certificate verify error :/

See if this video is of any help to you...
http://www.xda-developers.com/lg-g3-locked-bootloader-bump-xdatv/

That's what I did and it still gave me an error :/

I'm out of ideas... sorry.

redduc900 said:
I'm out of ideas... sorry.
Click to expand...
Click to collapse
No worries, I appreciate all of your help!

How do I backup my stock recovery?

I want to be able to flash my stock recovery when I no longer want TWRP or CWM. How would I go about doing this?

tcmoffitt said:
I want to be able to flash my stock recovery when I no longer want TWRP or CWM. How would I go about doing this?
Click to expand...
Click to collapse
Hello,
Thanks for using XDA Assist.
What device do you have?
___
v7
XDA Assist

v7 said:
Hello,
Thanks for using XDA Assist.
What device do you have?
___
v7
XDA Assist
Click to expand...
Click to collapse
HTC One m8 Tmobile

Thanks for the help guys I really appreciate it. This forum is just so helpful............. ---____---

Which T-Mobile ?
If it is T-Mob US .. there's a dedicated section for T-Mob US and you can find any info there.

tcmoffitt said:
Thanks for the help guys I really appreciate it. This forum is just so helpful............. ---____---
Click to expand...
Click to collapse
This is not possible to backup your stock recovery. When you need that you can download it simply (base on your phone's build number). Also you can extract stock recovery frome your ota zip update(the file with img format inside of firmware folder)

Arsinn said:
This is not possible to backup your stock recovery.
Click to expand...
Click to collapse
Actually, the following usually works:
This has to be done before flashing custom recovery. Unlock bootloader, then fastboot boot recovery.img
With "recovery.img" being a TWRP file located in your fasboot folder. This will boot into TWRP without actually flashing it. From there, you can pick recovery in the backup options, to backup stock recovery.
But yes, I agree that stock recovery images are pretty easy to obtain from these forums, or extracting from a OTA or ROM.zip.

redpoint73 said:
Actually, the following usually works:
This has to be done before flashing custom recovery. Unlock bootloader, then fastboot boot recovery.img
With "recovery.img" being a TWRP file located in your fasboot folder. This will boot into TWRP without actually flashing it. From there, you can pick recovery in the backup options, to backup stock recovery.
But yes, I agree that stock recovery images are pretty easy to obtain from these forums, or extracting from a OTA or ROM.zip.
Click to expand...
Click to collapse
Hi, redpoint73...
Maybe I'm missing something here, but I'm not seeing an option to backup the Recovery in TWRP 2.8.7.0... Just Boot, Cache, System, Data and Android Secure are available (see attached screenshot). I remote booted TWRP from my laptop, as I did when I rooted Marshmallow around a fortnight ago, in order to keep the stock recovery intact.
It would certainly be useful to be able to backup the stock recovery via TWRP... I just haven't found a way of accomplishing it .
-----
But a possible option to backup the stock recovery would be to use the Flashify app...
Remote boot TWRP from your PC, acquire root, and then run Flashify...
Flashify PlayStore link...
https://play.google.com/store/apps/details?id=com.cgollner.flashify
XDA discussion thread...
http://forum.xda-developers.com/showthread.php?t=2349847
This app uses <dd=if/of> commands to backup and potentially restore the boot and/or recovery images.
Although it does require root to work.
I've used Flashify on my Nexus 7 and Nexus 9 in the past, but never on my M8, except to backup... never to restore, so I cannot personally vouch for it's safety on the M8.
-----
What I'm unsure of about Flashify...
@redpoint73, @ckpv5, maybe you guys could shed some light on this...
Would such a <dd=if/of> created backup of stock recovery be flashable via fastboot?
And would it be safe to do so?
I know that TWRP uses <dd=if/of> commands, having looked through TWRPs logs... but I'm not quite sure how fastboot works when it comes to flashing stuff, and I'm very wary about doing it myself or recommending it for others.
Normally, you'd just use the Flashify app to restore any recovery/boot.img backups you've previously made...
But Flashify requires root to work, and with an unrooted system, this is isn't viable. So could one use fastboot in the normal way to flash such a previously made backup of the stock recovery?
-----
Anyhow, it's not critical at the moment for me, because I've not flashed TWRP to my M8, my stock recovery remains intact.
-----
I would recommend anybody reading this seeking to root their Marshmallow M8 to just remote boot TWRP from their PC with fastboot boot twrp.img (ie., don't actually flash it), perform an unrooted Nandroid backup first...
...and then flash Chainfire in the usual way.
This leaves the stock recovery intact, which will be required for future OTAs.
And there still might be some...
My Nexus 9 receives monthly security patches from Google (probably after the StageFright debacle of last year), and it may well be that the M8 will also continue to receive security patches, despite it being nearly two years old.
So you need to be ready... with an unrooted/untouched Nandroid of your own creation and the stock recovery.
I know that Chainfires systemless root method is supposed to address this issue, but if you're going to mess with system, you should have a Nandroid backup anyway...
...just in case.
Rgrds,
Ged.

Funny, I use the fastboot boot option to boot into TWRP saving my original recovery.