adb - How can I enable adbd during boot on Cyanogenmod?

I am stuck during the boot process, at first before entering the passphrase for /data and now at the SIM PIN screen. At this point, adb is inaccessible (normally adbd would start up after unlocking /data, etc.).

How can I start adbd during boot? This is a CM 10.2 userdebug build for i9300 with /default.prop (from initrd) containing:

ro.adb.secure=1
ro.secure=1
ro.allow.mock.location=0
ro.debuggable=1
persist.sys.usb.config=mtp,adb

I have also tried the following to no avail:

• Edit /init.rc, comment out the disabled line for service adbd.



• Edit /init.smdk4x12.usb.rc, add start adbd to the property:sys.usb.config=mtp trigger.


• Add persist.sys.usb.config=adb to /default.prop

Answer

Since Android 4.2.2, [USB debugging requires authentication], something that is not possible during boot. To disable this, set the following property in default.prop (inside initrd):

ro.adb.secure=0

Alternatively, copy ~/.android/adbkey.pub into the initial ramdisk of the boot/recovery image at /adb_keys. This preserves the secure feature while granting your key access.

This enables adbd for a short time. It seems that some process is setting sys.usb.config=mtp. To work around that, I applied this patch (perhaps only the start adbd part is necessary, I have only tested the below):

--- init.smdk4x12.usb.rc        2013-10-24 18:47:34.894857300 +0200

+++ init.smdk4x12.usb.rc        2013-10-24 18:47:40.775493943 +0200
@@ -12,10 +12,11 @@
 on property:sys.usb.config=mtp
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 04e8
-    write /sys/class/android_usb/android0/idProduct 685c
-    write /sys/class/android_usb/android0/functions ${sys.usb.config}
+    write /sys/class/android_usb/android0/idProduct 6860
+    write /sys/class/android_usb/android0/functions ${sys.usb.config},adb
     write /sys/class/android_usb/android0/enable 1

-    setprop sys.usb.state ${sys.usb.config}
+    start adbd
+    setprop sys.usb.state ${sys.usb.config},adb

 on property:sys.usb.config=mtp,adb
     write /sys/class/android_usb/android0/enable 0

You won't be able to get root (su) through this. For that, set:

ro.secure=0

Updating the initramfs block, the initramfs header field and the SHA1 ID (header) of the boot.img is not in the scope of this answer.