Template:RK3399-BuildFromSource
Contents
- 1 Build Openwrt/Friendlywrt
- 2 Build Buildroot
- 3 Build Other Linux
- 4 Build the code using scripts
- 5 Building AOSP from source
1 Build Openwrt/Friendlywrt
1.1 Download Code
Two versions are available, please choose as required:
1.1.1 FriendlyWrt 21.02
mkdir friendlywrt21-rk3399 cd friendlywrt21-rk3399 git clone https://github.com/friendlyarm/repo --depth 1 tools tools/repo init -u https://github.com/friendlyarm/friendlywrt_manifests -b master-v21.02 \ -m rk3399.xml --repo-url=https://github.com/friendlyarm/repo --no-clone-bundle tools/repo sync -c --no-clone-bundle
1.1.2 FriendlyWrt 23.05
mkdir friendlywrt23-rk3399 cd friendlywrt23-rk3399 git clone https://github.com/friendlyarm/repo --depth 1 tools tools/repo init -u https://github.com/friendlyarm/friendlywrt_manifests -b master-v23.05 \ -m rk3399.xml --repo-url=https://github.com/friendlyarm/repo --no-clone-bundle tools/repo sync -c --no-clone-bundle
1.2 First compilation step
./build.sh rk3399.mk # or rk3399-docker.mk
All the components (including u-boot, kernel, and friendlywrt) are compiled and the sd card image will be generated, then execute the following command to generate the image file for installing the system into the emmc:
./build.sh emmc-img
After making changes to the project, the sd card image needs to be repackaged by running the following command:
./build.sh sd-img
1.3 Secondary compilation steps
cd friendlywrt make menuconfig rm -rf ./tmp make -j${nproc} cd ../ ./build.sh sd-img ./build.sh emmc-img
1.4 Build u-boot only
./build.sh uboot
1.5 Build kernel only
./build.sh kernel
1.6 Build friendlywrt only
./build.sh friendlywrt
Or go to the friendlywrt directory and follow the standard openwrt commands. If you get an error with the above command, try using the following command to compile in a single thread:
cd friendlywrt make -j1 V=s
2 Build Buildroot
please refer to: Buildroot
3 Build Other Linux
3.1 Kernel and u-boot versions
Operating System | Kernel Version | U-boot version | Cross-compiler | Partition type | Packaging Tool | Kernel branch | Kernel configuration | U-boot branch | U-boot configuration |
---|---|---|---|---|---|---|---|---|---|
lubuntu | linux v4.4.y | u-boot v2014.10 | 6.4-aarch64 |
MBR | sd-fuse | nanopi4-linux-v4.4.y | nanopi4_linux_defconfig | nanopi4-v2014.10_oreo | rk3399_defconfig |
friendlycore-arm64 | |||||||||
friendlydesktop-arm64 | |||||||||
eflasher | |||||||||
buildroot | linux v4.19.y | u-boot v2017.09 |
11.3-aarch64 | GPT | sd-fuse | nanopi4-v4.19.y | nanopi4_linux_defconfig | nanopi4-v2017.09 | nanopi4_defconfig |
ubuntu-focal-desktop-arm64 | |||||||||
debian-bullseye-desktop-arm64 | |||||||||
debian-bullseye-minimal-arm64 | |||||||||
friendlycore-focal-arm64 | |||||||||
debian-bookworm-core-arm64 | |||||||||
ubuntu-noble-core-arm64 | |||||||||
openmediavault-arm64 | linux v6.1.y | u-boot v2017.09 |
11.3-aarch64 | GPT | sd-fuse |
nanopi-r2-v6.1.y |
nanopi4_linux_defconfig | ||
friendlywrt21 | GPT | nanopi4_linux_defconfig +friendlywrt.config | |||||||
friendlywrt21-docker | |||||||||
friendlywrt23 | |||||||||
friendlywrt23-docker |
- Kernel git repo:https://github.com/friendlyarm/kernel-rockchip
- U-boot git repo:https://github.com/friendlyarm/uboot-rockchip
- The cross-compile toolchain is located in the path: /opt/FriendlyARM/toolchain/
- The SD-Fuse is a helper script to make bootable SD card image.
- Click on MBR and GPT in the table to view the partition layout (configuration file) for each system.
3.2 Build kernel linux-v4.4.y
This section applies to the following operating systems:
lubuntu | eflasher | friendlydesktop-arm64 | friendlycore-arm64 |
Clone the repository to your local drive then build:
git clone https://github.com/friendlyarm/kernel-rockchip --single-branch --depth 1 -b nanopi4-linux-v4.4.y kernel-rockchip cd kernel-rockchip export PATH=/opt/FriendlyARM/toolchain/6.4-aarch64/bin/:$PATH touch .scmversion # Load configuration make ARCH=arm64 CROSS_COMPILE=aarch64-linux- nanopi4_linux_defconfig # Optionally, if you want to change the default kernel config # make ARCH=arm64 CROSS_COMPILE=aarch64-linux- menuconfig # Start building kernel make ARCH=arm64 CROSS_COMPILE=aarch64-linux- nanopi4-images -j$(nproc) # Start building kernel modules mkdir -p out-modules make ARCH=arm64 CROSS_COMPILE=aarch64-linux- INSTALL_MOD_PATH="$PWD/out-modules" modules -j$(nproc) make ARCH=arm64 CROSS_COMPILE=aarch64-linux- INSTALL_MOD_PATH="$PWD/out-modules" modules_install KERNEL_VER=$(make CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 kernelrelease) rm -rf $PWD/out-modules/lib/modules/${KERNEL_VER}/kernel/drivers/gpu/arm/mali400/ [ ! -f "$PWD/out-modules/lib/modules/${KERNEL_VER}/modules.dep" ] && depmod -b $PWD/out-modules -E Module.symvers -F System.map -w ${KERNEL_VER} (cd $PWD/out-modules && find . -name \*.ko | xargs aarch64-linux-strip --strip-unneeded)
After the compilation, the following files will be generated:
kernel.img | resource.img | The kernel modules are located in the out-modules directory |
Run your build:
Please refre to #Running the build
3.3 Build u-boot v2014.10
This section applies to the following operating systems:
lubuntu | eflasher | friendlydesktop-arm64 | friendlycore-arm64 |
Clone the repository to your local drive then build:
git clone https://github.com/friendlyarm/uboot-rockchip --single-branch --depth 1 -b nanopi4-v2014.10_oreo cd uboot-rockchip export PATH=/opt/FriendlyARM/toolchain/6.4-aarch64/bin/:$PATH make CROSS_COMPILE=aarch64-linux- rk3399_defconfig make CROSS_COMPILE=aarch64-linux-
After the compilation, the following files will be generated:
uboot.img | trust.img | rk3399_loader_v1.22.119.bin (aka MiniLoaderAll.bin) |
Installing the u-boot:
Please refre to #Running the build
3.4 Build kernel linux-v4.19.y
This section applies to the following operating systems:
ubuntu-focal-desktop-arm64 | debian-bullseye-desktop-arm64 | debian-bullseye-minimal-arm64 | friendlycore-focal-arm64 | ubuntu-noble-core-arm64 | debian-bookworm-core-arm64 | buildroot |
Clone the repository to your local drive then build:
git clone https://github.com/friendlyarm/kernel-rockchip --single-branch --depth 1 -b nanopi4-v4.19.y kernel-rockchip cd kernel-rockchip export PATH=/opt/FriendlyARM/toolchain/11.3-aarch64/bin/:$PATH touch .scmversion # Configuring the Kernel # Load default configuration make ARCH=arm64 CROSS_COMPILE=aarch64-linux- nanopi4_linux_defconfig # Optionally, load configuration for FriendlyWrt # make ARCH=arm64 CROSS_COMPILE=aarch64-linux- nanopi4_linux_defconfig friendlywrt.config # Optionally, if you want to change the default kernel config # make ARCH=arm64 CROSS_COMPILE=aarch64-linux- menuconfig # Start building kernel make ARCH=arm64 CROSS_COMPILE=aarch64-linux- nanopi4-images -j$(nproc) # Start building kernel modules mkdir -p out-modules make ARCH=arm64 CROSS_COMPILE=aarch64-linux- INSTALL_MOD_PATH="$PWD/out-modules" modules -j$(nproc) make ARCH=arm64 CROSS_COMPILE=aarch64-linux- INSTALL_MOD_PATH="$PWD/out-modules" modules_install KERNEL_VER=$(make CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 kernelrelease) rm -rf $PWD/out-modules/lib/modules/${KERNEL_VER}/kernel/drivers/gpu/arm/mali400/ [ ! -f "$PWD/out-modules/lib/modules/${KERNEL_VER}/modules.dep" ] && depmod -b $PWD/out-modules -E Module.symvers -F System.map -w ${KERNEL_VER} (cd $PWD/out-modules && find . -name \*.ko | xargs aarch64-linux-strip --strip-unneeded)
After the compilation, the following files will be generated:
kernel.img | resource.img | The kernel modules are located in the out-modules directory |
Run your build:
Please refre to #Running the build
3.5 Build kernel linux-v6.1.y
This section applies to the following operating systems:
friendlywrt21 | friendlywrt21-docker | friendlywrt23 | friendlywrt23-docker | openmediavault-arm64 |
Clone the repository to your local drive then build:
git clone https://github.com/friendlyarm/kernel-rockchip --single-branch --depth 1 -b nanopi-r2-v6.1.y kernel-rockchip cd kernel-rockchip export PATH=/opt/FriendlyARM/toolchain/11.3-aarch64/bin/:$PATH touch .scmversion # Configuring the Kernel # Load default configuration make CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 nanopi4_linux_defconfig # Optionally, load configuration for FriendlyWrt # make CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 nanopi4_linux_defconfig friendlywrt.config # Optionally, if you want to change the default kernel config # make CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 menuconfig # Start building kernel make CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 -j$(nproc) # Start building kernel modules mkdir -p out-modules && rm -rf out-modules/* make CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 INSTALL_MOD_PATH="$PWD/out-modules" modules -j$(nproc) make CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 INSTALL_MOD_PATH="$PWD/out-modules" modules_install KERNEL_VER=$(make CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 kernelrelease) [ ! -f "$PWD/out-modules/lib/modules/${KERNEL_VER}/modules.dep" ] && depmod -b $PWD/out-modules -E Module.symvers -F System.map -w ${KERNEL_VER} (cd $PWD/out-modules && find . -name \*.ko | xargs aarch64-linux-strip --strip-unneeded)
Pack the kernel.img and resource.img:
wget https://raw.githubusercontent.com/friendlyarm/sd-fuse_rk3399/kernel-6.1.y/tools/mkkrnlimg && chmod 755 mkkrnlimg wget https://raw.githubusercontent.com/friendlyarm/sd-fuse_rk3399/kernel-6.1.y/tools/resource_tool && chmod 755 resource_tool wget https://raw.githubusercontent.com/friendlyarm/sd-fuse_rk3399/kernel-6.1.y/prebuilt/boot/logo.bmp wget https://raw.githubusercontent.com/friendlyarm/sd-fuse_rk3399/kernel-6.1.y/prebuilt/boot/logo_kernel.bmp ./mkkrnlimg arch/arm64/boot/Image kernel.img mkdir kernel-dtbs cp -f arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4s.dtb kernel-dtbs/rk3399-nanopi4-rev09.dtb cp -f arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4s.dtb kernel-dtbs/rk3399-nanopi4-rev0a.dtb cp -f arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4se.dtb kernel-dtbs/rk3399-nanopi4-rev0b.dtb cp -f arch/arm64/boot/dts/rockchip/rk3399-nanopc-t4.dtb kernel-dtbs/rk3399-nanopi4-rev00.dtb ./resource_tool --dtbname kernel-dtbs/*.dtb logo.bmp logo_kernel.bmp
After the compilation, the following files will be generated:
kernel.img | resource.img | The kernel modules are located in the out-modules directory |
Run your build:
Please refre to #Running the build
3.6 Build u-boot v2017.09
This section applies to the following operating systems:
ubuntu-focal-desktop-arm64 | debian-bullseye-desktop-arm64 | debian-bullseye-minimal-arm64 | friendlycore-focal-arm64 | ubuntu-noble-core-arm64 | debian-bookworm-core-arm64 | buildroot |
Clone the repository to your local drive then build:
git clone https://github.com/friendlyarm/rkbin --single-branch --depth 1 -b friendlyelec git clone https://github.com/friendlyarm/uboot-rockchip --single-branch --depth 1 -b nanopi4-v2017.09 export PATH=/opt/FriendlyARM/toolchain/11.3-aarch64/bin/:$PATH cd uboot-rockchip/ ./make.sh nanopi4
After the compilation, the following files will be generated:
uboot.img | trust.img | rk3399_loader_v1.24.126.bin (aka MiniLoaderAll.bin) |
Run your build:
Please refre to #Running the build
3.7 Running the build
3.7.1 Install to target board
3.7.1.1 MBR partition
This section applies to the following operating systems:
lubuntu | eflasher | friendlydesktop-arm64 | friendlycore-arm64 |
The MBR partitioning is only used by the Linux v4.4 kernel. You can check the partition layout by clicking on this link: partmap. To write an image file, you can use the dd command. For example, in the parameter.template file, "0x00014000@0x00014000(kernel)" specifies that the kernel partition starts at 0x00014000, which is equivalent to 81920 in decimal. Therefore, the dd command should be as follows:
dd if=kernel.img of=/dev/mmcblk0 seek=81920
3.7.1.2 GPT partition
This section applies to the following operating systems:
ubuntu-focal-desktop-arm64 | debian-bookworm-core-arm64 | debian-bullseye-desktop-arm64 | debian-bullseye-minimal-arm64 |
friendlycore-focal-arm64 | ubuntu-noble-core-arm64 | friendlywrt21-kernel4 | buildroot |
friendlywrt21 | friendlywrt21-docker | friendlywrt23 | friendlywrt23-docker |
The OS uses GPT partitions by default which is using the Linux v4.19 and Linux v5.15 kernel, you can use the dd command, but be careful to choose the right output device:
- The SD/TF Card device node: /dev/mmcblk0
- The eMMC device node: /dev/mmcblk2
The following is an example of how to update the kernel to eMMC:
Use the 'parted' command to view the partition layout:
parted /dev/mmcblk2 print
Sample outputs:
Model: MMC BJTD4R (sd/mmc) Disk /dev/mmcblk2: 31.3GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 8389kB 12.6MB 4194kB uboot 2 12.6MB 16.8MB 4194kB trust 3 16.8MB 21.0MB 4194kB misc 4 21.0MB 25.2MB 4194kB dtbo 5 25.2MB 41.9MB 16.8MB resource 6 41.9MB 83.9MB 41.9MB kernel 7 83.9MB 134MB 50.3MB boot 8 134MB 2500MB 2366MB ext4 rootfs 9 2500MB 31.3GB 28.8GB ext4 userdata
as shown above, the resource partition is located at 5 and the kernel partition is located at 6. Use the dd command to write the resource.img and kernel.img files to these partitions, the commands are as follows:
dd if=resource.img of=/dev/mmcblk2p5 bs=1M dd if=kernel.img of=/dev/mmcblk2p6 bs=1M
If you want to update u-boot:
dd if=uboot.img of=/dev/mmcblk2p1 bs=1M
To update new driver modules, copy the newly compiled driver modules to the appropriate directory under /lib/modules.
3.7.2 Packaging and creating an SD image
To create a new OS image file, you need to use the "sd-fuse" packaging tool.
"sd-fuse" is a collection of scripts that can be used to create bootable SD card images for FriendlyElec boards. Its main features include:
- Creation of root filesystem images from a directory
- Building of bootable SD card images
- Simple compilation of kernel, U-Boot, and third-party drivers
Please click on the following link to find out more:
Kernel version | Packaging Tool |
---|---|
linux v4.4.y | sd-fuse |
linux v4.19.y | sd-fuse_rk3399/kernel-4.19 |
linux v6.1.y | sd-fuse_rk3399/kernel-6.1.y |
3.7.3 USB flashing
Note: kernel v4.4.y is not supported
3.7.3.1 Linux
Reboot the board and enter loader mode with the following command:
sudo reboot loader
To flash U-Boot and kernel using the "upgrade_tool_v2.17_for_linux" tool, please use the following command:
sudo upgrade_tool di -k kernel.img sudo upgrade_tool di -re resource.img sudo upgrade_tool di -u uboot.img sudo upgrade_tool RD
Note: "upgrade_tool" is a command-line tool provided by Rockchip for Linux operating systems (Linux_Upgrade_Tool).
4 Build the code using scripts
4.1 Download scripts and image files
git clone https://github.com/friendlyarm/sd-fuse_rk3399.git -b kernel-4.19 cd sd-fuse_rk3399 wget http://112.124.9.243/dvdfiles/RK3399/images-for-eflasher/friendlycore-focal-arm64-images.tgz tar xvzf friendlycore-focal-arm64-images.tgz
4.2 Compile the kernel
Download the kernel source code and compile it. the relevant image files in the friendlycore-focal-arm64 directory will be automatically updated, including the kernel modules in the file system:
git clone https://github.com/friendlyarm/kernel-rockchip --depth 1 -b nanopi4-v4.19.y kernel-rk3399 KERNEL_SRC=$PWD/kernel-rk3399 ./build-kernel.sh friendlycore-focal-arm64
4.3 Compile the kernel headers
git clone https://github.com/friendlyarm/kernel-rockchip --depth 1 -b nanopi4-v4.19.y kernel-rk3399 MK_HEADERS_DEB=1 BUILD_THIRD_PARTY_DRIVER=0 KERNEL_SRC=$PWD/kernel-rk3399 ./build-kernel.sh friendlycore-focal-arm64
4.4 Compile the uboot
Download the uboot source code and compile it. the relevant image files in the friendlycore-focal-arm64 directory will be automatically updated:
git clone https://github.com/friendlyarm/uboot-rockchip --depth 1 -b nanopi4-v2017.09 UBOOT_SRC=$PWD/uboot-rockchip ./build-uboot.sh friendlycore-focal-arm64
4.5 Generate new image
Repackage the image file in the friendlycore-focal-arm64 directory into sd card image:
./mk-sd-image.sh friendlycore-focal-arm64
After the command is completed, the image is in the out directory, you can use the dd command to make the SD boot card, for example:
dd if=out/rk3399-sd-friendlycore-focal-4.19-arm64-YYYYMMDD.img of=/dev/sdX bs=1M
5 Building AOSP from source
5.1 Hardware and Software Requirements
- Your computer should have at least 16GB of RAM and 300GB of disk space. We recommend using a machine with 32GB of RAM and a large-capacity, high-speed SSD, and we do not recommend using virtual machines.
- If you encounter compilation errors, they may be caused by problems with the compilation environment. We recommend using the following Docker container for compilation: docker-cross-compiler-novnc.
5.2 Compile Android10
5.2.1 Download Android10 Source Code
There are two ways to download the source code:
- repo archive file on netdisk
Netdisk URL: Click here
File location on netdisk:"07_Source codes/rk3399-android-10.git-YYYYMMDD.tar.xz" (YYYYMMDD means the date of packaging)
After extracting the repo package from the network disk, you need to execute the sync.sh script, which will pull the latest code from gitlab:
tar xf "/path/to/netdisk/07_Source codes/rk3399-android-10.git-YYYYMMDD.tar.xz" cd rk3399-android-10 ./sync.sh
- git clone from gitlab
{{{1}}} source code is maintained in gitlab, You can download it by running the following command:
git clone --recursive https://gitlab.com/friendlyelec/rk3399-android-10.git -b main
Note: If the following error "error: unknown option `recurse-submodules'" appears, please upgrade git to v2.0.0 or above.
5.2.2 Generate Image File
You can compile an Android source code and generate an image file (non-root user is recommended):
cd rk3399-android-10 ./build-nanopc-t4.sh -F -M
If you need to include google apps, you need to set an environment variable and then compile, as shown below:
cd rk3399-android-10 export INSTALL_GAPPS_FOR_TESTING=yes ./build-nanopc-t4.sh -F -M
5.2.3 Make OTA Packages
If you need the support of A/B (Seamless) System Updates, you need to do the following:
a) Build your own update server for http download of update files;
b) Customize the Updater application, the code is located in packages/apps/Updater, let it connect and download file from your server;
c) Use the quick compilation script parameter -O or --ota to compile OTA Packages, as shown below:
cd rk3399-android-10 ./build-nanopc-t4.sh -F -O -M
After the compilation is successfully completed, the OTA update related packages are located in the directory: rockdev/otapackage/ ,Please do not delete this directory.
After you have made some changes, compiling again with the parameter -O will generate ota-update-XXXXXXXX.zip, which is an incremental update package.
OTA Packages decides whether to generate incremental update package according to BUILD_NUMBER, for details, please refer to build-nanopc-t4.sh.
To disable the A/B feature, you can refer to the following to modify device/rockchip/rk3399/nanopc-t4/BoardConfig.mk, and then recompile uboot and android:
BOARD_USES_AB_IMAGE := false
5.2.4 Update System with New Image
After compilation is done a new image file will be generated in the "rockdev/Image-nanopc_t4/" directory under Android 10's source code directory. You can follow the steps below to update the OS in {{{1}}}:
1) Insert an SD card which is processed with EFlasher to an SD card reader and insert this reader to a PC running Ubuntu. The SD card's partitions will be automatically mounted;
2) Copy all the files under the "rockdev/Image-nanopc_t4/" directory to the SD card's android10 directory in the "FRIENDLYARM" partition;
3) Insert this SD card to {{{1}}} and reflash Android
When flashing Android 10, EFlasher requires v1.3 or above. When flashing with Type-C, please use the tool AndroidTool v2.71 or Linux_Upgrade_Tool v1.49 provided by Rockchip.
5.3 Compile Android8.1
5.3.1 Download Android8.1 Source Code
There are two ways to download the source code:
- repo archive file on netdisk
Netdisk URL: Click here
File location on netdisk:sources/rk3399-android-8.1.git-YYYYMMDD.tgz (YYYYMMDD means the date of packaging)
After extracting the repo package from the network disk, you need to execute the sync.sh script, which will pull the latest code from gitlab:
tar xvzf /path/to/netdisk/sources/rk3399-android-8.1.git-YYYYMMDD.tgz cd rk3399-android-8.1 ./sync.sh
- git clone from gitlab
{{{1}}} source code is maintained in gitlab, You can download it by running the following command:
git clone https://gitlab.com/friendlyelec/rk3399-android-8.1 --depth 1 -b master
5.3.2 Generate Image File
You can compile an Android source code and generate an image file:
cd rk3399-android-8.1 ./build-nanopc-t4.sh -F -M
5.3.3 Update System with New Image
After compilation is done a new image file will be generated in the "rockdev/Image-nanopc_t4/" directory under Android 8.1's source code directory. You can follow the steps below to update the OS in {{{1}}}:
1) Insert an SD card which is processed with EFlasher to an SD card reader and insert this reader to a PC running Ubuntu. The SD card's partitions will be automatically mounted;
2) Copy all the files under the "rockdev/Image-nanopc_t4/" directory to the SD card's android8 directory in the "FRIENDLYARM" partition;
3) Insert this SD card to {{{1}}} and reflash Android
Here is an alternative guide to update OS: sd-fuse_rk3399
5.4 Compile Android7
5.4.1 Download Android7 Source Code
There are two ways to download the source code:
- repo archive file on netdisk
Netdisk URL: Click here
File location on netdisk:sources/rk3399-android-7.git-YYYYMMDD.tgz (YYYYMMDD means the date of packaging)
After extracting the repo package from the network disk, you need to execute the sync.sh script, which will pull the latest code from gitlab:
tar xvzf /path/to/netdisk/sources/rk3399-android-7.git-YYYYMMDD.tgz cd rk3399-nougat ./sync.sh
- git clone from gitlab
{{{1}}} source code is maintained in gitlab, You can download it by running the following command:
git clone https://gitlab.com/friendlyelec/rk3399-nougat --depth 1 -b nanopc-t4-nougat
5.4.2 Generate Image File
You can compile an Android7 source code and generate an image file:
cd rk3399-nougat ./build-nanopc-t4.sh -F -M
5.4.3 Update System with New Image
After compilation is done a new image file will be generated in the "rockdev/Image-nanopc_t4/" directory under Android7's source code directory. You can follow the steps below to update the OS in {{{1}}}:
1) Insert an SD card which is processed with EFlasher to an SD card reader and insert this reader to a PC running Ubuntu. The SD card's partitions will be automatically mounted;
2) Copy all the files under the "rockdev/Image-nanopc_t4/" directory to the SD card's android8 directory in the "FRIENDLYARM" partition;
3) Insert this SD card to {{{1}}} and reflash Android
Here is an alternative guide to update OS: sd-fuse_rk3399