Lenovo Tab M8 (FHD) (TB-8705F): How to root?

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foureight84

Member
Mar 28, 2011
12
0
Are there currently any custom roms for this device? I made the mistake of upgrading to android 10 and it's pretty slow even after factory reset. I've tried disabling a few stock lenovo packages via adb and it seems to help but still more sluggish than android 9.
 
Thanks so much for the link! I am trying the site, but it is telling me I have to upgrade my upgrade my download package even after selecting the smallest sized file they have uploaded, so that's probably not going to work out in the long run.

Are you using the Lenovo Rescue and Recover to be able to restore the Android 9 Firmware or using Fastboot commands? Are you getting an error when you attempt the downgrade?

There are 2 different devices being mentioned here, the 8505f, hardware code 6761 and the 8705, hardware code 6762, that have different hardware. But the naming convention is similar.

This was the version on my M8 8505 when I got it. The S100* is android 9.
TB-8505F_MT6761_HW61_S100102_
tb-8505FS-USR-S100145_2009010959 is the last update of 9 before 10 was released.

This is the current version it wants to update to. The S300* is android 10.
tb-8505FS-USR_S30025_

Thanks for that clarification I am indeed using the 8705 model.
 

GBAFan

Member
Jan 1, 2021
13
1
Are you using the Lenovo Rescue and Recover to be able to restore the Android 9 Firmware or using Fastboot commands? Are you getting an error when you attempt the downgrade?
The rescue tool. It's odd because the process seemingly works fine up until I have to plug the tablet back in, once that happens it instantly goes to 100% completion, but with no visible changes to the device at all. I've used the tool successfully before to restore to the current Android 10 firmware, so I have no idea why it is not working with the firmware I grabbed from the two websites I found it on. Might just be bad firmware?
 

retro5

Member
Dec 5, 2020
17
6
The rescue tool. It's odd because the process seemingly works fine up until I have to plug the tablet back in, once that happens it instantly goes to 100% completion, but with no visible changes to the device at all. I've used the tool successfully before to restore to the current Android 10 firmware, so I have no idea why it is not working with the firmware I grabbed from the two websites I found it on. Might just be bad firmware?
How big is the folder after you unzip into it? I have several versions and they are all over 3gb, with 24 or 25 files, the largest file is system.img at 2.9gb. Maybe you just got an update and not a full rom?? If you can find an older rom to install, it will get the updates one at a time until the 10 upgrade and you can chose when or if to install them.
 

GBAFan

Member
Jan 1, 2021
13
1
How big is the folder after you unzip into it? I have several versions and they are all over 3gb, with 24 or 25 files, the largest file is system.img at 2.9gb. Maybe you just got an update and not a full rom?? If you can find an older rom to install, it will get the updates one at a time until the 10 upgrade and you can chose when or if to install them.
The only file I have been able to find and download is TB-8705F_S100099_200706_BMP.zip which is 1.59Gb zipped up. I'm not sure if that's an update or the full rom, now that you mention that point. I've looked around and it seems like all the 8705f roms and updates are non-existent aside from paysites, and I would rather not pay to get something that Lenovo should have freely available for people who bought a Lenovo device.
 

retro5

Member
Dec 5, 2020
17
6
The only file I have been able to find and download is TB-8705F_S100099_200706_BMP.zip which is 1.59Gb zipped up. I'm not sure if that's an update or the full rom, now that you mention that point. I've looked around and it seems like all the 8705f roms and updates are non-existent aside from paysites, and I would rather not pay to get something that Lenovo should have freely available for people who bought a Lenovo device.
Maybe if you ask in the other M8 thread someone will have a rom. lsrgish has an 8705 and has ported TWRP working with 10, but he might have a 9 rom.
 

ricardordz20

New member
Jan 4, 2021
2
0
Finally got it to root after starting from scratch again.
The Steps below are what worked for me using Windows 10.
Note: using the latest ADB/Fastboot was the cause of all of my problems since fastboot refused to detect my device. I had to use the ADB and fastboot that came with the Rescue program and everything went easy after that.

1. Download and Install Lenovo Rescue and Smart Assistant
2. Tap on build number in Settings>System 7 times to enable Developer Mode
3. Settings>System>Developer Options - tick OEM unlock & USB debugging in developer settings
4. Connect Tablet to Computer
5. Download latest firmware from Lenovo Rescue and Smart Assistant using the Rescue tab.
6. Access CMD or Powershell from C:\Program Files (x86)\Rescue and Smart Assistant. (This is so that it uses the ADB and Fastboot that comes with the Rescue program. Downloading and using the latest ADB/Fastboot refused to find the device)
7. In powershell type: "adb reboot bootloader" This will reboot the tablet into fastboot mode.
8. Type in "fastboot devices" and verify a device shows up. If it doesn't, you will have to fiddle until it does. (I had to disconnect and reconnect while the tablet was in Fastboot mode for it to recognize the first time.)
9. Type in "fastboot flashing unlock" and follow prompts on the tablet (Vol+ for mine)
10. Reboot tablet into Android
10. Copy boot.img out of the firmware zip file downloaded previously and transfer it to the downloads folder on the tablet
11. Download and Install the Magisk Manager APK onto the tablet (it's not in the Play Store)
12. Open Magisk Manager on the tablet, Allow it permissions.
13. Power down and back up into Android
14. Open Magisk Manager on the tablet
15. Install Magisk from within the Magisk Manager App, and select the boot.img in your downloads folder. Allow it permissions.
16. Move newly generated magisk_patched.img to your computer in terminal-appropriate folder (I used the C:\ to keep it simple)
17. Access CMD or Powershell from C:\Program Files (x86)\Rescue and Smart Assistant. (This is so that it uses the ADB and Fastboot that comes with the Rescue program. Downloading and using the latest ADB/Fastboot refused to find the device)
18. In powershell type: "adb reboot bootloader" This will reboot the tablet into fastboot mode.
19. Type in "fastboot devices" and verify a device shows up.
20. Type in "fastboot flash boot C:\magisk_patched.img" (If you put the file in C:\) Took 6.4 seconds on mine.
21. Unplug and Reboot Tablet. It should say Orange Status as it boots and pause for 5 seconds before booting into Android.
22. Check for root. (I used Root Checker from the Play Store)

Hey! A little late! I appreciate the detailed guide. I followed all your steps but I am stuck on the Lenovo splash with the orange status. I know I can unbrick it with the device rescue, but I'm not sure why I can't get root acess. Everything works according to your guide except to the part where I have to flash the patched .img file. Would love some help! Thanks!!
 
Last edited:
Hey! A little late! I appreciate the detailed guide. I followed all your steps but I am stuck on the Lenovo splash with the orange status. I know I can unbrick it with the device rescue, but I'm not sure why I can't get root acess. Everything works according to your guide except to the part where I have to flash the patched .img file. Would love some help! Thanks!!

If you are rooting Android 10 check this post.

For the new Update for this tablet that is Android 10. See This post on Android Enthusiasts for how to root.
 

retro5

Member
Dec 5, 2020
17
6
Hey! A little late! I appreciate the detailed guide. I followed all your steps but I am stuck on the Lenovo splash with the orange status. I know I can unbrick it with the device rescue, but I'm not sure why I can't get root acess. Everything works according to your guide except to the part where I have to flash the patched .img file. Would love some help! Thanks!!
You didn't say which device you are trying to root or which android version, that helps us help you.
What's missing from the list is when you get the boot.img from the new rom, also get the vbmeta.img and put them in the same folder.
Also, after unlocking the bootloader #10, when you boot back into the os and go through setup, do a minimum setup, but reenable dev options and turn on usb debug and reinstall magisk.

Then starting with #19 in the list add the 'disable' cmd before flashing the patched img.

adb reboot bootloader
fastboot --disable-verification flash vbmeta D:\dnlds\vbmeta.img
fastboot flash boot D:\dnlds\magisk_patched.img
 
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ricardordz20

New member
Jan 4, 2021
2
0
You didn't say which device you are trying to root or which android version, that helps us help you.
What's missing from the list is when you get the boot.img from the new rom, also get the vbmeta.img and put them in the same folder.
Also, after unlocking the bootloader #10, when you boot back into the os and go through setup, do a minimum setup, but reenable dev options and turn on usb debug and reinstall magisk.

Then starting with #19 in the list add the 'disable' cmd before flashing the patched img.

adb reboot bootloader
fastboot --disable-verification flash vbmeta D:\dnlds\vbmeta.img
fastboot flash boot D:\dnlds\magisk_patched.img

Thanks, for the tips. I followed the steps and I manged to reboot it. When I use root checker, however it says "root access is not properly installed on this device."

Lenovo TB-8505FS
Android 10.
 
Last edited:

m1xmstr

Member
Oct 24, 2014
42
30
Wyoming
SOLUTION -- Updated 01/05/2020
######################################################
Are you sick and tired of not having root access on your M8 FHD with Android 10!

Magisk Manager -> Gear Icon
Update Channel -> From Stable to Beta

Now you should be on 21.2 (as of Jan 5 2020).

Now patch the boot.img and the magisk_patched_RANDOM_Letters.img will be 32MB -- Previously I was getting a 10MB patched file!

Then adb reboot bootloader

fastboot devices #Verify your device

fastboot flash boot C:\PATH_TO\magisk_patched_BLAHBLAH.img

fastboot --disable-verification flash vbmeta C:\PATH_TO\vbmeta_disabled.img

fastboot flash boot C:\PATH_TO\magisk_patched_BLAHBLAH.img

fastboot reboot

Now go to Magisk Manager (Mine looked like a default apk icon now), and it will show that magisk is installed on the device, and a prompt will say it needs to install an additional zip or something to the fact.

The device will reboot after you say ok

NOW check for root, and "Bob's your Uncle" a toast appears asking if you want to grant root access.

FINALLY!

I used this mostly blank vbmeta_disable.img (found somewhere on this thread), not sure if a it is needed or if the regular vbmeta.img will work feel free to try either...

#M1XMSTR
 

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mamba76

Senior Member
Apr 16, 2018
73
7
I bought the same tablet to replace the 2013 nexus 7 I have running in my honda fit. For the lenovo to work I need the tablet to support otg charging. On the nexus 7 I installed timur's kernel to make that work. On this as far as I can tell, I need to update a flag in the kernel per these docs, https://android.googlesource.com/ke...-marshmallow-dr/Documentation/usb/msm_otg.txt (search for ID_C in the ACA section). Any help would be appreciated on accomplishing that.
Thanks,
Peter
GOOGLE LAVASYNC ------------------------------------ OTG AND CHARGE ))
 

jeno1957

Member
Jun 10, 2012
30
0
Unlocked Bootloader

According to some posts, when bootloader is unlocked
--tablet goes into Orange State
--waits for 5 sec
--displays message " bootloader unlocked"

Could somebody confirm that above are correct ?
Is this after "unlock" process only or at every boot all the time ?
If permanent, Is there a "fix" for these to have a "normal" looking boot ?
Can a bootloader re-locked by re-flasing original boot.img?

Thank You !
 
Last edited:

Ryccardo

Senior Member
Nov 12, 2013
509
171
25
Imola
According to some posts, when bootloader is unlocked
--tablet goes into Orange State
--waits for 5 sec
--displays message " bootloader unlocked"

Could somebody confirm that above are correct ?
Is this after "unlock" process only or at every boot all the time ?
On every boot - and it's just some text that appears over the bootlogo, just like on the Nexus 5, a bit ugly but not that much of a big deal, how often do you reboot anyway (once you have decided which rom you really want)? :)

Can a bootloader re-locked by re-flasing original boot.img?
Not exactly like that but yes: first you lock the bootloader (fastboot flashing lock) then you restore all modified partitions (I did this using spflash, which the official lenovo recovery program is a frontend for), and yes it gets rid of the unlocked warning unlike on the Moto E for example!
 
For the 8705-F stock Android 10 image there seems to be a new Android 10 update. Hopefully fix some of the bugs we have with this image. It's labeled TB-8705F_USR_S30043_2101271807_V9.56_BMP_ROW.

My device is rooted using the method listed here and using Magisk. To take this update do I simply need to restore the Boot.img in Magisk or something more since we replaced the vbmeta?
 
Since I havent got any replies I'll journal what I have done to see if I can get this to work.

4/13 - I tried to uninstall Magisk and take the update it said it was missing the stock boot.img so I decided to wipe the device (nothing was on it anyway).
After wiping the device still not able to update to the ota. Tried to relock the bootloader but it wont let me so. Maybe I can restore the orginal vbmeta and maybe that will fix it. Will try and update when I return.
 

Isrgish

Senior Member
Jan 5, 2018
87
11
Since I havent got any replies I'll journal what I have done to see if I can get this to work.

4/13 - I tried to uninstall Magisk and take the update it said it was missing the stock boot.img so I decided to wipe the device (nothing was on it anyway).
After wiping the device still not able to update to the ota. Tried to relock the bootloader but it wont let me so. Maybe I can restore the orginal vbmeta and maybe that will fix it. Will try and update when I return.
You need to restore the original boot.img and the vbmeta.img as well. If you installed any changed recovery you will need to restore that original as well.
 

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  • 2
    For the new Update for this tablet that is Android 10. See This post on Android Enthusiasts for how to root.
    2
    I hate to be that new guy asking for help, but I recently obtained a Tab 8 FHD and while I love the hardware, Android 10 is just awful on it for me. I saw the earlier post about using the renamed Android 9 firmware and LMSA to install 9 on the FHD, but after trying it unsuccessfully with the two different firmware files I found online I have had zero luck.

    I have tried the TB-8705F_S100099_200706_BMP firmware from two different, possibly sketchy sites, since I could not find the official Lenovo release and all other options I could find were pay to DL. So does anyone happen to have a link to any of the Android 9 firmware files that's safe and complete? I know I'm probably asking a lot, but I really like the FHD and I would like to be able to use it properly, and not gimped by Android 10.
    Have you looked at this site 8705f ? If you go back a level he also has firmware folders for the 8705N and 8705X. I used one from there with no problems.
    1
    Hey! A little late! I appreciate the detailed guide. I followed all your steps but I am stuck on the Lenovo splash with the orange status. I know I can unbrick it with the device rescue, but I'm not sure why I can't get root acess. Everything works according to your guide except to the part where I have to flash the patched .img file. Would love some help! Thanks!!
    You didn't say which device you are trying to root or which android version, that helps us help you.
    What's missing from the list is when you get the boot.img from the new rom, also get the vbmeta.img and put them in the same folder.
    Also, after unlocking the bootloader #10, when you boot back into the os and go through setup, do a minimum setup, but reenable dev options and turn on usb debug and reinstall magisk.

    Then starting with #19 in the list add the 'disable' cmd before flashing the patched img.

    adb reboot bootloader
    fastboot --disable-verification flash vbmeta D:\dnlds\vbmeta.img
    fastboot flash boot D:\dnlds\magisk_patched.img
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