Installation Instructions
Before Magisk installs anything on your device, it will create a boot image backup in /data/stock_boot_<sha1>.img.gz
If anything goes wrong (e.g. bootloop), you can either use the uninstaller (recommended) or decompress the backup and manually restore your boot image
It should ALWAYS bring your device back to life (suppose you have a custom recovery that can decrypt your /data)
If you're already rooted with MagiskSU or Latest Official Systemless SuperSU
Install/upgrade Magisk Manager from Play Store
Install/upgrade Magisk as prompted in the application
Reboot and you're done!!
If you're not rooted, or something went wrong and you need a clean start
(Recommended) Restore your boot image back to stock (flash uninstaller if Magisk is previously installed)
Download the latest Magisk zip file
Reboot to a custom recovery
If you choose to use SuperSU (only support Android 6.0+), flash SuperSU in systemless mode now
Flash Magisk zip
Reboot. Update the stub Magisk Manager to the latest from Play Store
https://forum.xda-developers.com/apps/magisk/official-magisk-v7-universal-systemless-t3473445