setup variables for commands

echo -e "\n
export image=redroid/redroid:11.0.0-amd64
export image_tar=${HOME}/redroid:11.0.0-amd64" >> ${HOME}/.bashrc
source ${HOME}/.bashrc

1 is recommended

1. using docker method

preserve original redroid image

sudo docker pull $image
sudo docker save --output redroidBak.tar $image

backup or install original redroid image

# remove the changed image if exist
sudo docker image rmi -f $image
# install the original image
sudo docker load -i redroidBak.tar

2.using moby method

preserve original redroid image

wget -q "https://raw.githubusercontent.com/moby/moby/master/contrib/download-frozen-image-v2.sh" -P ~ ; chmod u+x ~/download-frozen-image-v2.sh

~/download-frozen-image-v2.sh "$image_tar" redroid/redroid:11.0.0-amd64

backup or install original redroid image

# remove the changed image if exist
sudo docker image rmi -f $image
# install the original image
tar -cC "$image_tar" . | sudo docker load

setting up

mkdir ~/MagiskOnRedroid
cd ~/MagiskOnRedroid

download+extract magisk

find -maxdepth 1 -iname "magisk*" -not -name "*.apk" -exec rm -r {} \;
magisk_file="app-debug.apk"
# download Magisk 9b61bdfc(25201) debug as you did i guess
if [ ! -f $magisk_file ]; then
  wget "https://cdn.jsdelivr.net/gh/topjohnwu/magisk-files@1cea72840fbf690f9a95512d03721f6a710fe02e/app-debug.apk"
fi
# because my machine x64 i will choose x86_64
unzip -j $magisk_file "lib/x86_64/libmagisk64.so" -d magisk
unzip -j $magisk_file "lib/x86_64/libbusybox.so" -d magisk
mv -v magisk/libmagisk64.so magisk/magisk
mv -v magisk/libbusybox.so magisk/busybox
# $ tree ~/MagiskOnRedroid
# .
# ├── app-debug.apk
# └── magisk
#     ├── busybox
#     └── magisk

compress magisk

tar --transform 's/.*\///g' -cf ~/magisk.tar --absolute-names $( find ~/MagiskOnRedroid | grep -E "magisk/|app-debug.apk$" )

remove.rc

cat <<\EOF > ~/remove.rc
on early-init
	export PATH /sbin:/product/bin:/apex/com.android.runtime/bin:/apex/com.android.art/bin:/system_ext/bin:/system/bin:/system/xbin:/odm/bin:/vendor/bin:/vendor/xbin
	chmod 0700 /magisk.tar
	chown root root /magisk.tar
	chmod 0700 /setup.sh
	chown root root /setup.sh
	exec root root -- /setup.sh
service magisk-d /sbin/magisk --daemon
	user root
	oneshot
on boot
	start magisk-d
on post-fs-data
	start logd
	rm /dev/.magisk-unblock
	start s1
	wait /dev/.magisk-unblock 5
	rm /dev/.magisk-unblock
service s1 /sbin/magisk --post-fs-data
	user root
	oneshot
service s2 /sbin/magisk --service
	class late_start
	user root
	oneshot
on property:sys.boot_completed=1
	exec /sbin/magisk --boot-complete
on property:init.svc.zygote=restarting
	exec /sbin/magisk --zygote-restart
on property:init.svc.zygote=stopped
	exec /sbin/magisk --zygote-restart
EOF
sudo chmod 644 ~/remove.rc
sudo chown root:root ~/remove.rc

setup.sh

cat <<\EOF > ~/setup.sh
#!/system/bin/sh

# rm /system/fonts/NotoColorEmoji.ttf
tmpPushed=/magisk
rm -rf $tmpPushed
mkdir $tmpPushed
tar -xvf /magisk.tar --no-same-owner -C $tmpPushed
umount /magisk.tar ; rm -v /magisk.tar
mkdir /sbin
chown root:root /sbin
# chmod 0700 /sbin
chmod 0751 /sbin
cp $tmpPushed/magisk /sbin/
cp $tmpPushed/app-debug.apk /sbin/stub.apk
find /sbin -type f -exec chmod 0755 {} \;
find /sbin -type f -exec chown root:root {} \;
# add /sbin
# /sbin/
# ├── magisk
# └── stub.apk


ln -f -s /sbin/magisk /system/xbin/su
mkdir /product/bin
chmod 751 /product/bin
ln -f -s /sbin/magisk /product/bin/su
# add su (override `/system/xbin/su`)
# /product/bin/
# └── su -> /sbin/magisk

mkdir -p /data/adb/magisk
chmod 700 /data/adb
mv $tmpPushed/busybox /data/adb/magisk/
chmod -R 755 /data/adb/magisk
chmod -R root:root /data/adb/magisk
# /data/adb/
# ├── magisk
# │   └── busybox

# rm -rf $tmpPushed
EOF
sudo chmod 700 ~/setup.sh
sudo chown root:root ~/setup.sh

to get magisk working do this:

1. phase
   • boot with magisk support

   (
   sudo docker stop a11
   clear
   sudo docker run -itd --rm --privileged \
     --name a11 \
     -v ~/data:/data \
     -v ~/remove.rc:/vendor/etc/init/remove.rc \
     -v ~/setup.sh:/setup.sh \
     -v ~/magisk.tar:/magisk.tar \
     -p 5555:5555 \
     redroid/redroid:11.0.0-amd64 \
     ro.secure=0
   )