关于定制设备Android系统的方法研究
目标：在设备系统中集成我的服务
1. 了解Android系统
1.1 Android系统固件组成
- recovery.img TWRP
- update.zip
- boot.img
- data/ init.rc开机执行你希望执行的命令
- system/ 是一系列希望放到系统中的工具
- META-INF/
1.2 Android系统的启动模式
2. 备份原系统ROM
- Android系统开放root权限
- adb shell 进行系统
- su 切入root权限
- dd if=/dev/block/mmcblk0p3 of=/sdcard/system.img 备份system分区
- dd if=/dev/block/mmcblk0p2 of=/sdcard/boot.img 备份boot.img
3. 修改原系统ROM
4. 刷入修改后的新系统ROM
LineageOS
一个第三方开源编译Android系统，最接近于Android原生，并支持大量设备型号。
为加快速度，将源代码先以镜像方式下载。
$ cd YOUR_MIRROR_PATH
$ repo init -u https://github.com/LineageOS/android.git -b lineage-18.1 --mirror
$ repo sync --no-tags
$ cd ~/android/lineage
$ repo init -u https://github.com/LineageOS/android.git -b lineage-18.1 --reference=YOUR_MIRROR_PATH
$ repo sync
编译记录
$ vi .repo/local_manifests/roomservice.xml
<?xml version="1.0" encoding="UTF-8"?>
<manifest>
<project name="LineageOS/android_device_xiaomi_dipper" path="device/xiaomi/dipper" remote="github" />
<project name="LineageOS/android_device_xiaomi_sdm845-common" path="device/xiaomi/sdm845-common" remote="github" />
<project name="LineageOS/android_hardware_xiaomi" path="hardware/xiaomi" remote="github" />
<project name="LineageOS/android_kernel_xiaomi_sdm845" path="kernel/xiaomi/sdm845" remote="github" />
</manifest>
$ source build/envsetup.sh
$ breakfast dipper
Looking for dependencies in device/xiaomi/dipper
Looking for dependencies in device/xiaomi/sdm845-common
Looking for dependencies in hardware/xiaomi
hardware/xiaomi has no additional dependencies.
Looking for dependencies in kernel/xiaomi/sdm845
kernel/xiaomi/sdm845 has no additional dependencies.
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=11
LINEAGE_VERSION=18.1-20210908-UNOFFICIAL-dipper
TARGET_PRODUCT=lineage_dipper
TARGET_BUILD_VARIANT=userdebug
TARGET_BUILD_TYPE=release
TARGET_ARCH=arm64
TARGET_ARCH_VARIANT=armv8-a
TARGET_CPU_VARIANT=generic
TARGET_2ND_ARCH=arm
TARGET_2ND_ARCH_VARIANT=armv8-a
TARGET_2ND_CPU_VARIANT=generic
HOST_ARCH=x86_64
HOST_2ND_ARCH=x86
HOST_OS=linux
HOST_OS_EXTRA=Linux-5.10.0-8-amd64-x86_64-Debian-GNU/Linux-11-(bullseye)
HOST_CROSS_OS=windows
HOST_CROSS_ARCH=x86
HOST_CROSS_2ND_ARCH=x86_64
HOST_BUILD_TYPE=release
BUILD_ID=RQ3A.210805.001.A1
OUT_DIR=out
PRODUCT_SOONG_NAMESPACES=device/xiaomi/sdm845-common hardware/google/interfaces hardware/google/pixel hardware/xiaomi vendor/nxp/opensource/pn5xx hardware/qcom-caf/sdm845 vendor/qcom/opensource/commonsys-intf/display vendor/qcom/opensource/data-ipa-cfg-mgr vendor/qcom/opensource/dataservices vendor/qcom/opensource/commonsys/packages/apps/Bluetooth vendor/qcom/opensource/commonsys/system/bt/conf
============================================
proprietary blobs 设备专有blobs
Extracting proprietary blobs from LineageOS zip files
文中讲了三种方式，分别是基于:
- Block-based OTA
- File-based OTA
- Payload-based OTA
blobs我理解为由硬件（开发版）厂商提供的硬件接口驱动等文件。
device specific configuration 设备特定配置
kernel 设备内核
实操小米手机
1. 解小米手机BL锁
基于厂商SDK编译Android系统
固件定制演练
1. 解包
-rw-r--r-- 1 wii wii 314368784 9月 9 17:35 AIO-3288C_Android8.1_Beta_180810.7z
# 逐层解包
$ 7z e AIO-3288C_Android8.1_Beta_180810.7z
-rw-r--r-- 1 wii wii 883786200 8月 9 2018 AIO-3288C_Android8.1_Beta_180810.img
$ file AIO-3288C_Android8.1_Beta_180810.img
AIO-3288C_Android8.1_Beta_180810.img: data
$ vim -b AIO-3288C_Android8.1_Beta_180810.img
00000000: 524b 4657 6600 0000 0107 0000 0601 e207 RKFWf...........
00000010: 0809 143a 3a80 0000 0066 0000 004e 6902 ...::....f...Ni.
00000020: 00b4 6902 0004 18ab 3400 0000 0001 0000 ..i.....4.......
00000030: 0000 0000 0010 0100 0000 0000 0000 0000 ................
00000040: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000050: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000060: 0000 0000 0000 424f 4f54 6600 3602 0000 ......BOOTf.6...
:%!xxd
$ sudo apt-get install rkflashtool
$ rkunpack AIO-3288C_Android8.1_Beta_180810.img
rkunpack: info: RKFW signature detected
rkunpack: info: version: 7.1.0
rkunpack: info: date: 2018-08-09 20:58:58
rkunpack: info: family: rk32xx
rkunpack: info: 00000066-000269b3 BOOT (size: 158030)
rkunpack: info: 000269b4-34ad81b7 embedded-update.img (size: 883628036) # 升级包
unpacked
$ rkunpack embedded-update.img
rkunpack: info: RKAF signature detected
rkunpack: info: file size matches (883628036 bytes)
rkunpack: info: manufacturer: rk3288
rkunpack: info: model: RK3288
rkunpack: info: number of files: 14
rkunpack: info: 00000800-00000800 package-file (size: 697)
rkunpack: info: 00001000-0000104d Image/MiniLoaderAll.bin (size: 158030)
rkunpack: info: 00028000-00028000 Image/parameter.txt (size: 871)
rkunpack: info: 00028800-00028fff Image/trust.img (size: 4194304)
rkunpack: info: 00428800-00428fff Image/uboot.img (size: 4194304)
rkunpack: info: 00828800-00828817 Image/misc.img (size: 49152)
rkunpack: info: 00834800-00834868 Image/resource.img (size: 213504)
rkunpack: info: 00869000-00869f58 Image/kernel.img (size: 8046348)
rkunpack: info: 01015800-01015aa1 Image/boot.img (size: 1379068)
rkunpack: info: 01166800-01167652 Image/recovery.img (size: 7509088)
rkunpack: info: 01890000-018e4b52 Image/system.img (size: 710578420) # 系统分区,根/目录
rkunpack: info: 2be39800-2be4b040 Image/vendor.img (size: 146931836) # 底层分区,里面有设备底层驱动
rkunpack: info: 34a5a000-34a5a0ae Image/oem.img (size: 356452)
rkunpack: info: 00000000-ffffffff RESERVED (size: 0)
unpacked
# system.img 格式转换
$ file system.img
system.img: Android sparse image, version: 1.0, Total of 524288 4096-byte output blocks in 18 input chunks.
$ sudo apt-get install simg2img
$ simg2img system.img system_raw.img
$ file system_raw.img
system_raw.img: Linux rev 1.0 ext4 filesystem data, UUID=115d422f-283c-4425-a525-6e68ab4836e6, volume name "system" (extents) (64bit) (large files) (huge files)
# 挂载 system.img
$ mkdir system
$ sudo mount -o loop system_raw.img system
wii@wiiD:/media/wii/d1/AIO-3288C_Android8.1/Image$ ll system
总用量 168
drwxr-xr-x. 42 root root 4096 8月 9 2018 app # 存放app
drwxr-xr-x. 3 root 2000 8192 8月 9 2018 bin
-rw-------. 1 root root 1928 8月 9 2018 build.prop
-rw-r--r--. 1 root root 74748 8月 9 2018 compatibility_matrix.xml
drwxr-xr-x. 10 root root 4096 8月 9 2018 etc
drwxr-xr-x. 2 root root 4096 8月 9 2018 fake-libs
drwxr-xr-x. 2 root root 8192 8月 9 2018 fonts
drwxr-xr-x. 4 root root 4096 8月 9 2018 framework
drwxr-xr-x. 6 root root 12288 8月 9 2018 lib
drwxr-xr-x. 2 root root 4096 8月 9 2018 lib64
drwx------. 2 root root 16384 8月 9 2018 lost+found
-rw-r--r--. 1 root root 2946 8月 9 2018 manifest.xml
drwxr-xr-x. 3 root root 4096 8月 9 2018 media
drwxr-xr-x. 39 root root 4096 8月 9 2018 priv-app # 存放app
drwxr-xr-x. 3 root root 4096 8月 9 2018 tts
drwxr-xr-x. 8 root root 4096 8月 9 2018 usr
lrw-r--r--. 1 root root 7 8月 9 2018 vendor -> /vendor
drwxr-xr-x. 2 root 2000 4096 8月 9 2018 xbin
# 对system进行写操作需要root权限
2. 修改
$ sudo cp busybox system/bin
$ sudo chown 0.2000 system/bin/busybox
$ sudo chmod 755 system/bin/busybox
$ cd system/bin
$ sudo ln -s busybox run-parts
$ sudo chown 0.2000 run-parts
$ sudo chmod 755 run-parts
$ sudo ln -s busybox crond
$ sudo ln -s busybox crontab
$ sudo ln -s busybox vi
$ ll busybox
-rwxr-xr-x. 1 root 2000 280000 9月 10 08:46 busybox
$ ll run-parts
lrwxrwxrwx 1 root 2000 7 9月 10 08:51 run-parts -> busybox
$ sudo vi sysinit
#!/system/bin/sh
# init.d support
export PATH=/sbin:/system/sbin:/system/bin:/system/xbin
run-parts /system/etc/init.d
$ sudo chmod 755 sysinit
$ sudo chown 0.2000 sysinit
$ ll sysinit
-rwxr-xr-x 1 root 2000 121 9月 10 09:02 sysinit
$ cd ../etc
sudo vi install-recovery.sh
#!/system/bin/sh
# init.d support
/system/bin/sysinit
$ sudo chown 0.0 install-recovery.sh
$ sudo chmod 755 install-recovery.sh
$ sudo mkdir init.d
$ sudo vi init.d/08setperm
#!/system/bin/sh
# set correct permissions to /system/etc/init.d folder
mount -o remount,rw -t auto /system
chmod -R 777 /system/etc/init.d
mount -o remount,ro -t auto /system
$ sudo vi init.d/00test
#!/system/bin/sh
#init.d test
if [ -f /data/Test.log ]; then
rm /data/Test.log
fi
echo "Init.d is working !!!" >> /data/Test.log
echo "executed on $(date +"%d-%m-%Y %r" )" >> /data/Test.log
$ sudo chmod 777 init.d -R
$ sudo chown 0.0 init.d -R
$ cd ../../
3. 重新打包
# sudo apt-get install android-sdk-ext4-utils Debian 10/11 已经不提供
# 注意：Pandaboard中一下语句的“ -s ”参数不能省略！如果省略了“ -s ”参数，虽然可以生产system.img文件！但是你用“ simg2img system.img system.img.ext4 ”时会报错！
# 这个工具代码在Android源代码中 system/extras/ext4_utils
# https://packages.debian.org/buster/android-tools-fsutils 下载旧版本的安装包 android-tools-fsutils_5.1.1.r38-1.1_amd64.deb
# 因其与系统的android-sdk-libsparse-utils有冲突，先卸载之前安装的simg2img
# sudo apt-get remove simg2img android-sdk-libsparse-utils
# sudo dpkg -i android-tools-fsutils_5.1.1.r38-1.1_amd64.deb
# -s 制作ext4格式文件系统
# -T 时间戳
# -S 上下文文件
# -L 标签
# -l 1610612736:分区的大小为1.5G (1610612736的大小为1.5G)
# -a system 是指这个img用于android系统，挂载点是/system
# $ sudo make_ext4fs -s -T 0 -S file_contexts -l 1024M -a system system_new.img system
$ sudo make_ext4fs -s -T 0 -l 1024M -a system system_new.img system
Creating filesystem with parameters:
Size: 1073741824
Block size: 4096
Blocks per group: 32768
Inodes per group: 8192
Inode size: 256
Journal blocks: 4096
Label:
Blocks: 262144
Block groups: 8
Reserved block group size: 63
Created filesystem with 2238/65536 inodes and 173297/262144 blocks
$ file system.img
system.img: Android sparse image, version: 1.0, Total of 524288 4096-byte output blocks in 18 input chunks.
$ file system_new.img
system_new.img: Android sparse image, version: 1.0, Total of 262144 4096-byte output blocks in 2077 input chunks.
$ sudo make_ext4fs -s -T 0 -l 2048M -a system system_new.img system
Creating filesystem with parameters:
Size: 2147483648
Block size: 4096
Blocks per group: 32768
Inodes per group: 8192
Inode size: 256
Journal blocks: 8192
Label:
Blocks: 524288
Block groups: 16
Reserved block group size: 127
Created filesystem with 2238/131072 inodes and 181954/524288 blocks
$ file system_new.img
system_new2.img: Android sparse image, version: 1.0, Total of 524288 4096-byte output blocks in 2096 input chunks.
# 由此判断原system.img应该是按分区2G创建的
# 我将新创建system_new.img重新转换挂在后可看之前增加的内容，发现bin目录下的内容正常，但新建sbin以及etc/init.d目录及文件的权限均不对。
# 应该是上一步缺少 -S file_contexts 上下文文件造成的
$ vi system/etc/selinux/plat_file_contexts
/system/sbin/busybox u:object_r:busybox_shell_exec:s0
/system/sbin/run-parts u:object_r:run_parts_exec:s0
/system/etc/init.d(/.*)? u:object_r:init_d_exec:s0
$ sudo make_ext4fs -s -T 0 -S system/etc/selinux/plat_file_contexts -l 2048M -a system system_new3.img system
# 测试没有起作用
# https://github.com/naobsd/rkutils
$ ./rkafpack manufacturer:rk3288 machine_model:RK3288 package-file:package-file bootloader:Image/MiniLoaderAll.bin parameter:Image/parameter.txt trust:Image/trust.img uboot:Image/uboot.img misc:Image/misc.img resource:Image/resource.img kernel:Image/kernel.img boot:Image/boot.img recovery:Image/recovery.img system:Image/system.img vendor:Image/vendor.img oem:Image/oem.img backup:RESERVED > embedded-update_new.img
$ ll embedded-update*.img
-rw-r--r-- 1 wii wii 883628036 9月 9 18:01 embedded-update.img
-rw-r--r-- 1 wii wii 884303876 9月 10 11:11 embedded-update_new.img
$ rkunpack embedded-update.img
rkunpack: info: RKAF signature detected
rkunpack: info: file size matches (883628036 bytes)
rkunpack: info: manufacturer: rk3288
rkunpack: info: model: RK3288
rkunpack: info: number of files: 14
rkunpack: info: 00000800-00000800 package-file (size: 697)
rkunpack: info: 00001000-0000104d Image/MiniLoaderAll.bin (size: 158030)
rkunpack: info: 00028000-00028000 Image/parameter.txt (size: 871)
rkunpack: info: 00028800-00028fff Image/trust.img (size: 4194304)
rkunpack: info: 00428800-00428fff Image/uboot.img (size: 4194304)
rkunpack: info: 00828800-00828817 Image/misc.img (size: 49152)
rkunpack: info: 00834800-00834868 Image/resource.img (size: 213504)
rkunpack: info: 00869000-00869f58 Image/kernel.img (size: 8046348)
rkunpack: info: 01015800-01015aa1 Image/boot.img (size: 1379068)
rkunpack: info: 01166800-01167652 Image/recovery.img (size: 7509088)
rkunpack: info: 01890000-018e4b52 Image/system.img (size: 710578420)
rkunpack: info: 2be39800-2be4b040 Image/vendor.img (size: 146931836)
rkunpack: info: 34a5a000-34a5a0ae Image/oem.img (size: 356452)
rkunpack: info: 00000000-ffffffff RESERVED (size: 0)
unpacked
$ rkunpack embedded-update_new.img
rkunpack: info: RKAF signature detected
rkunpack: info: file size matches (884303876 bytes)
rkunpack: info: manufacturer: rk3288
rkunpack: info: model: RK3288
rkunpack: info: number of files: 14
rkunpack: info: 00000800-00000fff package-file (size: 697)
rkunpack: info: 00001000-00027fff Image/MiniLoaderAll.bin (size: 158030)
rkunpack: info: 00028000-000287ff Image/parameter.txt (size: 859)
rkunpack: info: 00028800-004287ff Image/trust.img (size: 4194304)
rkunpack: info: 00428800-008287ff Image/uboot.img (size: 4194304)
rkunpack: info: 00828800-008347ff Image/misc.img (size: 49152)
rkunpack: info: 00834800-00868fff Image/resource.img (size: 213504)
rkunpack: info: 00869000-010157ff Image/kernel.img (size: 8046348)
rkunpack: info: 01015800-011667ff Image/boot.img (size: 1379068)
rkunpack: info: 01166800-0188ffff Image/recovery.img (size: 7509088)
rkunpack: info: 01890000-2bede7ff Image/system.img (size: 711254632)
rkunpack: info: 2bede800-34afefff Image/vendor.img (size: 146931836)
rkunpack: info: 34aff000-34b567ff Image/oem.img (size: 356452)
rkunpack: info: 34b56800-34b567ff RESERVED (size: 0)
unpacked
公司rk3399设备Android系统研究
# df
Filesystem 1K-blocks Used Available Use% Mounted on
rootfs 1958172 4844 1953328 1% /
tmpfs 1968168 436 1967732 1% /dev
tmpfs 1968168 0 1968168 0% /mnt
/dev/block/mmcblk1p10 1499760 774096 725664 52% /system
/dev/block/mmcblk1p9 124912 176 124736 1% /cache
/dev/block/mmcblk1p11 12016 40 11976 1% /metadata
/dev/block/mmcblk1p15 27956876 4851076 23105800 18% /data
/data/media 27956876 4851076 23105800 18% /mnt/runtime/default/emulated
/data/media 27956876 4851076 23105800 18% /mnt/runtime/read/emulated
/data/media 27956876 4851076 23105800 18% /mnt/runtime/write/emulated
# mount
rootfs on / type rootfs (ro,seclabel,size=1958172k,nr_inodes=489543)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)
proc on /proc type proc (rw,relatime,gid=3009,hidepid=2)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
/sys/kernel/debug on /sys/kernel/debug type debugfs (rw,seclabel,relatime,mode=755)
/sys/kernel/debug/tracing on /sys/kernel/debug/tracing type tracefs (rw,seclabel,relatime,mode=755)
none on /acct type cgroup (rw,relatime,cpuacct)
none on /dev/stune type cgroup (rw,relatime,schedtune)
tmpfs on /mnt type tmpfs (rw,seclabel,relatime,mode=755,gid=1000)
none on /config type configfs (rw,relatime)
none on /dev/memcg type cgroup (rw,relatime,memory)
none on /dev/cpuctl type cgroup (rw,relatime,cpu)
none on /dev/cpuset type cgroup (rw,relatime,cpuset,noprefix,release_agent=/sbin/cpuset_release_agent)
pstore on /sys/fs/pstore type pstore (rw,seclabel,relatime)
/dev/block/mmcblk1p10 on /system type ext4 (ro,seclabel,noatime,nodiratime,noauto_da_alloc,data=ordered) # <--
/dev/block/mmcblk1p9 on /cache type ext4 (rw,seclabel,nosuid,nodev,noatime,nodiratime,discard,noauto_da_alloc,data=ordered)
/dev/block/mmcblk1p11 on /metadata type ext4 (rw,seclabel,nosuid,nodev,noatime,nodiratime,discard,noauto_da_alloc,data=ordered)
/dev/block/mmcblk1p15 on /data type ext4 (rw,dirsync,seclabel,nosuid,nodev,noatime,nodiratime,discard,noauto_da_alloc,errors=panic,data=ordered)
tmpfs on /storage type tmpfs (rw,seclabel,relatime,mode=755,gid=1000)
adb on /dev/usb-ffs/adb type functionfs (rw,relatime)
/data/media on /mnt/runtime/default/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6)
/data/media on /storage/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6)
/data/media on /mnt/runtime/read/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=23)
/data/media on /mnt/runtime/write/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7)
# ls -l /dev/block/platform/fe330000.sdhci/by-name/
total 0
lrwxrwxrwx 1 root root 20 2021-09-10 17:31 backup -> /dev/block/mmcblk1p8
lrwxrwxrwx 1 root root 20 2021-09-10 17:31 boot -> /dev/block/mmcblk1p6
lrwxrwxrwx 1 root root 20 2021-09-10 17:31 cache -> /dev/block/mmcblk1p9
lrwxrwxrwx 1 root root 21 2021-09-10 17:31 frp -> /dev/block/mmcblk1p14
lrwxrwxrwx 1 root root 20 2021-09-10 17:31 kernel -> /dev/block/mmcblk1p5
lrwxrwxrwx 1 root root 21 2021-09-10 17:31 metadata -> /dev/block/mmcblk1p11
lrwxrwxrwx 1 root root 20 2021-09-10 17:31 misc -> /dev/block/mmcblk1p3
lrwxrwxrwx 1 root root 20 2021-09-10 17:31 recovery -> /dev/block/mmcblk1p7
lrwxrwxrwx 1 root root 21 2021-09-10 17:31 reserved -> /dev/block/mmcblk1p13
lrwxrwxrwx 1 root root 20 2021-09-10 17:31 resource -> /dev/block/mmcblk1p4
lrwxrwxrwx 1 root root 21 2021-09-10 17:31 system -> /dev/block/mmcblk1p10
lrwxrwxrwx 1 root root 20 2021-09-10 17:31 trust -> /dev/block/mmcblk1p2
lrwxrwxrwx 1 root root 20 2021-09-10 17:31 uboot -> /dev/block/mmcblk1p1
lrwxrwxrwx 1 root root 21 2021-09-10 17:31 userdata -> /dev/block/mmcblk1p15
lrwxrwxrwx 1 root root 21 2021-09-10 17:31 verity_mode -> /dev/block/mmcblk1p12
$ su
# mount -o remount,rw /dev/block/mmcblk1p10 /system
mount: '/system' not in /proc/mounts
$ adb root
$ adb disable-verity
$ adb remount
$ adb shell
问题 : WARNING: linker: /system/bin/busybox: unsupported flags DT_FLAGS_1=0x8000001
并不影响使用
操boot.img
工具所在位置:
- kernel/scripts/mkkrnlimg
- out/host/linux-x86/bin/mkbootfs
- system/core/cpio/mkbootfs.c
- out/host/linux-x86/bin/mkbootimg
- system/core/mkbootimg/mkbootimg
1. 解包
$ file boot.img
boot.img: data <-KRNL->
$ mkkrnlimg -r boot.img boot.img-ramdisk.gz
$ file boot.img-ramdisk.gz
boot.img-ramdisk.gz: gzip compressed data, from Unix, original size modulo 2^32 4832000
$ mkdir ramdisk
$ cd ramdisk
$ gzip -dc ../boot.img-ramdisk.gz | cpio -i
2. 修改
$ vi init.rc
service initd /system/bin/sysinit
class main
user root
group root
oneshot
3. 重构
$ out/host/linux-x86/bin/mkbootfs -d out/target/product/nanopc-t4/system out/target/product/nanopc-t4/root | out/host/linux-x86/bin/minigzip > out/target/product/nanopc-t4/ramdisk.img
$ out/host/linux-x86/bin/mkbootimg --kernel out/target/product/nanopc-t4/kernel --ramdisk out/target/product/nanopc-t4/ramdisk.img --cmdline \"buildvariant=userdebug\" --os_version 7.1.2 --os_patch_level 2017-04-05 --output out/target/product/nanopc-t4/boot.img"
$ rkst/mkkrnlimg $OUT/ramdisk.img $IMAGE_PATH/boot.img
$ find . | cpio -o -H newc | gzip > ../newramdisk.cpio.gz
$ cd ..
$ mkkrnlimg -a newramdisk.cpio.gz boot_new.img