how to install magisk on Android 7.1.1 (Nougat) Intel x86 Atom_64 System Image android studio guest, linux host

1. start emulator
2. install file manager that can be used as file picker like total commander in guest
3. install magisk apk in guest
4. create boot.img:

   sh /path/to/brimg r2b < /path/to/ramdisk.img > /tmp/not-patched-boot.img

   • note: ramdisk.img is located in ~/Android/Sdk/system-images/android-25/default/x86_64 (~ is home directory) for me
5. upload boot.img to guest:

   adb push /tmp/not-patched-boot.img /storage/emulated/0/not-patched-boot.img

6. patch not-patched-boot.img using magisk app in guest
7. download patched boot.img to host:

   adb pull /storage/emulated/0/Download/magisk_patched-blah_blah.img /tmp/patched-boot.img

   • note: magisk_patched-blah_blah.img will be different for you
8. exit emulator
9. replace ramdisk.img:

   sh /path/to/brimg b2r < /tmp/patched-boot.img > /path/to/ramdisk.img