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utagboot for Motorola Droid 4 xt894 With utagboot we can configure droid 4 utags partition to boot to any partition on the device using the stock Linux kernel that comes with the device. This tool just generates a utags partition file. The way utagboot works is by modifying the stock kernel command line arguments using the utags partition on the device. The utags partition seems to be for custom ATAGs that also show up on the kernel command line. The utags partition can be easily erased and flashed with fastboot. USAGE Typically utagboot is used together with a kexec based minimal rootfs, such as droid4-kexecboot. Please see the README for droid4-kexecboot for more information: https://github.com/tmlind/droid4-kexecboot DEPENDENCIES Shell, Make and fastboot on your PC. Usable Linux rootfs on a partition with recent kexec-tools on the device. LIMITATIONS USING THE STOCK KERNEL With the stock kernel, CONFIG_VT is disabled making it not very friendly for distro use. And the LCD seems to operate only in manual update mode, so using the LCD needs customized software. Further, the stock kernel seems to have some issues, for example warm reset can cause the device to reboot multiple times. And there are issues trying to use the stock kernel and a newer kernel with the same distro with stock kernel wanting to use /dev/ttyO2 while newer should be using /dev/ttyS2 for serial console. To work around these issues, it's best to use the stock kernel to boot to a Linux distro on a selected root partition enough to just kexec boot a newer kernel. Also note that kexec booting older v3.0.8 based kernels needs to be done with the custom kexec binary that comes with SafeStrap. And it seems that Lineage OS currently has a dependency to the SafeStrap loop devices being configured. REFERENCES For more information how utags work, see "fastboot oem vuln: Android Bootloader Vulnerabilities in Vendor Customizations" by Roee Hay. I don't think the related fastboot oem to modify utags are available on droid 4 though.