Basically I just wanted to have my Titanium Backup working again after the OTA-Update…
This insecure boot image was created from factory image nakasi-jop40c-factory-6aabb391.tgz;
build number JOP40C (that’s codename “grouper”).
It requires a) the “Google Nexus 7 ADB Interface” to be installed,
b) that /tools and /platform-tools are defined within the $PATH
and c) that the device’s boot-loader is already OEM unlocked.
First, open a terminal or MS-DOS prompt and boot into the bootloader menu:
adb reboot bootloader
To download the image-file and boot it once (it’s rather not recommend to flash it):
fastboot boot boot-insecure-jop40c-nakasi.img
downloading 'boot.img'... OKAY [ 0.656s] booting... OKAY [ 0.016s] finished. total time: 0.672s
The device should boot until the X (or swirling dots) are displayed, no further.
Next, to remount the system partition read/write:
adb shell mount -o rw,remount -t ext4 /dev/block/platform/sdhci-tegra.3/by-name/APP /system
To install su & busybox (after further updates it’s ordinary enough to push/chmod su only):
adb push su /system/bin adb push SuperSU_0.98.apk /system/app/ adb push busybox /system/xbin/ adb shell chmod 06755 /system/bin/su adb shell chmod 0644 /system/app/SuperSU_0.98.apk adb shell chmod 04755 /system/xbin/busybox
And finally, just reboot.
adb shell reboot
Since Android 5.1 Lollipop has SE Linux enabled …it’s probably easier to:
a) upload SuperSU-v2.46.zip to SD card and b) boot into recovery, by entering:
fastboot boot recovery-clockwork-126.96.36.199-grouper.img
and c) select “Update from SD” and then choose the SuperSU-v2.46.zip – done.