MF800_V4.1/alpine_chroot

Setup

• Download the lastest alpine-minirootfs for armv7 from alpinelinux
• Once you have root access use adb to push these files to /data/ (e.g. adb push setup.sh /data/):
  • alpine-minirootfs-3.22.1-armv7.tar.gz
  • setup.sh
  • busybox-armv7l
• Navigate to /data and then run sh setup.sh which should setup the chroot (mounting the /dev etc)
• This will then drop you into a localhost shell, to get out

Start Up Scripts

• To start up a binary we need to insert a script somewhere in the start up procedure, I noted that the binary debuggerd is started and didn't think we needed this so instead replaced the binary with a shell script that would start my own programs.
• Android mounts its /system/bin as read only so it is necessary to temporarily remount this to make the changes:
  • mount -o remount,rw /system
  • chmod o+w /system/bin
  • Backup debuggerd binary and then replace it with the shell script
  • chmod o-w /system/bin
  • mount -o remount,ro /system

Links

• alpine-minirootfs
• Setting up chroot
• android - changing system permissions