Android Rooting

Thoughts about rooting

Since 2021 November I’ve reverted back to an unrooted phone. This is the first time I’ve gone unrooted in a decade, since I got my first phone. Unfortunately the reality is that rooting is getting more troublesome, and I get fewer benefits out of doing so.

When the Android ecosystem was still new, custom ROMs added a ton of new and interesting functionality. For a while I used Paranoid Android ROMs, which introduced a unique gesture navigations and floating bubbles. They were several years ahead of official iOS and Android implementations of the same, and even then, the ROM’s implementation had more functionality.

ROMs with such levels of customizability seem to have waned though. Likely because such features involved deep changes into the system, which would frequently get broken by new updates. Frankly as I get older, I’m not too interested being on the bleeding edge anymore. System stability is more important to me now.

For the past few years, the only reason I still rooted my phone was to get system-wide adblock. The least intrusive method for this is simply to update the /etc/hosts file on the system.

Recently apps have been detecting root in increasingly sophisticated ways. Google also introduced hardware attestation to further prevent users from hiding their rooted status from apps. Bypassing these checks is no longer trivial. Furthermore, some apps – notably banking apps – are now outright blocking users who are rooted.

In light of the new restrictions on rooted phones, I’ve decided to revert back to an unrooted phone. I’m not ready to give up on system-wide adblock however. I’m using the free version of Blokada to do so. The free version runs a VPN on your phone and performs DNS based host blocking, which is similar to editing the /etc/hosts file. It works pretty well.

I trust Blokada a reasonable amount to use it. Though when I have more time I’d like to fork DNS66 or some other open-source VPN adblocker and build it myself, so I can vet the code for assurance that the app isn’t harvesting my browsing data.

Rooting Pixel 3a

• TWRP can’t be installed on Android 10+ without first downgrading to Android 9

To install magisk, patch the boot image instead.

1. Download the factory image
2. Extract boot.img from the factory image
3. Transfer boot.img to your device
4. In Magisk Manager, select Install > Install > Select and patch a file
5. Magisk Manager will patch the image, and store it in [Internal Storage]/Download/magisk_patched.img
6. Copy the patched image to your PC
7. Boot into fastboot by first powering off the phone, then booting it while holding Power + Volume Down.
8. Flash the patched boot image using fastboot flash boot /path/to/magisk_patched.img

Installing OTAs

Skip the normal uninstall magisk > install ota > install magisk to inactive slot flow, it’s inconsistent at best. Just use the sideload method.

1. Download the factory image from https://developers.google.com/android/images
2. Download the OTA image from https://developers.google.com/android/ota
3. Extract boot.img from the factory image
4. Transfer boot.img to your phone
5. In Magisk Manager, patch boot.img (assuming the output file is magisk_patched.img for the remaining steps)
6. Transfer magisk_patched.img back to your computer
7. Boot into recovery (e.g. adb reboot recovery)
8. Sideload the OTA with adb sideload ./path/to/OTA.zip
9. Boot into fastboot
10. Apply the patched boot image with fastboot flash boot ./magisk_patched.img
11. Reboot

Common issues

Stuck in fastboot loop:

• boot.img might be malformed. Try flashing the stock boot image.
• Device might be trying to boot from the wrong A/B partition. Change the active partition with fastboot --set-active=[a/b]

Magisk patched boot.img does not work

• Magisk stable channel might not be updated yet. Use the canary app, select the canary channel and try again.