這篇文章介紹如何構建一個完整基於ARM的Ubuntu系統。

由於改文章當初寫的時候是發表在國外產品論壇上面，故保留了原文內容。

補充說明：

雖然Geekbox是基於8核64Bits Cortex-A53 ARMV8架構的CPU，該方法構建的時候採用了向下相容的32Bits的ARMV7架構。因此，該方法適用於Cortex-A7/A9/A15/A17/A12架構的ARM處理器。

In this guide, we will describe how to build an ubuntu system for Geekbox from scratch.

Different ways to achieve it:
1. Build the whole system in host PC with Chroot(emulator)
Link: TBD
2. Build in a removable media device, such as: SDCard or UDisk
Link: TBD
3. Build in the target device directly
Link: current article


Before starting
Carry on the following questions before you start your work:
1. Q: armhf vs arm64
A: Google for the answer

2. Q: Ubuntu vs Lubuntu/Kubuntu
A: Google for the answer

3. Q: What is included in an ubuntu system?
A: Bootloader & ramfs(kernel + initrd) & rootfs

4. Q: how to manage your ubuntu projects
A: Continue current reading and think about your own manage mothod.

Preparations

1. Create the working directories

$ install -d ~/project/geekbox/ubuntu/{linux,initrd,rootfs,prebuilts,archives/{ubuntu-core,debs,hwpacks},images,utils,scripts}
$ cd ~/project/geekbox/ubuntu

2. Download the bootloader source code

$ git clone https://github.com/geekboxzone/lollipop_u-boot u-boot

3. Download the linux kernel source code

$ git clone https://github.com/geekboxzone/lollipop_kernel -b ubuntu linux
 

4. Download the toolchain

$ git clone https://github.com/geekboxzone/lollipop_prebuilts_gcc_linux-x86_aarch64_aarch64-linux-android-4.9.git prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/

Note the full path of "prebuilts/gcc/linux-x86/arm/arm-eabi-4.6", just to keep [email protected] happy

5. Download the initrd

$ git clone https://github.com/gouwa/initrd.git initrd

6. Download the hardware packages for Geekbox

$ git clone https://github.com/geekboxzone/ubuntu_hwpacks.git archives/hwpacks

7. Download the ubuntu-core

$ wget -P archives/ubuntu-core http://cdimage.ubuntu.com/ubuntu-core/releases/14.04.3/release/ubuntu-core-14.04.3-core-armhf.tar.gz

Visit the following link for the more versions:
[url]http://cdimage.ubuntu.com/ubuntu-core/releases[/url]


8. Download the rockchip upgrade tool, note to specify the "ubuntu" branch:

$ git clone https://github.com/geekboxzone/utils.git -b ubuntu utils

[Optional]If you want to run the command in any path:

$ sudo cp -a utils/upgrade_tool /usr/local/bin

9. Download the rockchip mkbootimg tools

$ git clone https://github.com/neo-technologies/rockchip-mkbootimg.git mkbootimg

Build and install mkbootimg tools:

$ make -C mkbootimg/
$ sudo make install -C mkbootimg/

The above steps will generate some files in /usr/local/bin/
See utils/mkbootimg/README.md file for more information


All the preparatory works above are necessary to build an ubuntu.
And we also offter some scripts to do thus work:
10. [Optional]Download the scripts:

$ git clone https://github.com/geekboxzone/ubuntu_scripts.git scripts

All the steps above just need to run one time, even if you will build the Ubuntu system many times.


Build the bootloader
1. Compile:

$ make rk3368_box_defconfig -C u-boot/
$ make ARCHV=aarch64 -C u-boot/

2. Copy the images to the image directory:

$ cp -a u-boot/RK3368MiniLoaderAll_V*.bin u-boot/uboot.img u-boot/trust.img images/

Build the initial ramdisk
1. Compile the kernel

$ alias Make='make ARCH=arm64'
$ Make -C linux ugeekbox_defconfig
$ Make -C linux geekbox.img -j8

or 7.9-inch CrossDisplay

$ Make -C linux cross.img -j8

2. Copy the images to the image directory:

$ cp -a linux/resource.img images/

3. Compile the initrd

$ make -C initrd

SHA match for u-boot:

$ truncate -s "%4" images/initrd.img

View SecureNSModeBootImageShaCheck() function in following file for the information:
u-boot/board/rockchip/common/SecureBoot/SecureVerify.c


4. Generate the ramfs.img

$ mkbootimg --kernel linux/arch/arm64/boot/Image --ramdisk images/initrd.img -o images/ramfs.img

[b]Build the rootfs[/b]
Notice: Many following steps need the root privileges, do not forget to type sudo if necessary.
1. Create a blank image file using dd:

$ dd if=/dev/zero of=images/rootfs.img bs=1M count=256

Modify the count value as you want.
NOTE: if you want to build the rootfs on the host PC, recommend 2.5GB for GUI building.


2. Create linux filesystem on the newly created image:

$ mkfs.ext4 -F -L linuxroot images/rootfs.img

Notice: "linuxroot" is the volume-label of the rootfs, it MUST BE EXACTLY MATCH the CMDLINE in parameter:

CMDLINE: console=ttyS2 root=LABEL=linuxroot

Otherwise, there will be similar mistakes as follow when mount the rootfs:
[quote]Gave up waiting for root device.  Common problems:
 - Boot args (cat /proc/cmdline)
   - Check rootdelay= (did the system wait long enough?)
   - Check root= (did the system wait for the right device?)
 - Missing modules (cat /proc/modules; ls /dev)
ALERT!  /dev/disk/by-label/<unmatch-label> does not exist.  Dropping to a shell!
(initramfs)[/quote]
3. Confirm that rootfs is an empty directory!!!

$ rm -rf rootfs && mkdir rootfs

4. Loop mount the the new image:

$ sudo mount -o loop images/rootfs.img rootfs

5. Remove the unnecessary files

$ sudo rm -rf rootfs/lost+found

6. Extract the ubuntu-core tarball into the mounted dir:

$ sudo tar xzf archives/ubuntu-core/ubuntu-core-14.04.3-core-armhf.tar.gz -C rootfs/

Tips: ubuntu-core is the minimal root file system. 


7. Add hardware packages

$ sudo cp -a archives/hwpacks/system/ rootfs/

8. Add Wifi & Bluetooth support

$ sudo cp archives/hwpacks/wifibt/wifion rootfs/usr/local/bin/
$ sudo cp archives/hwpacks/wifibt/wifioff rootfs/usr/local/bin/
$ sudo cp archives/hwpacks/wifibt/wifi.conf rootfs/etc/init
$ sudo cp archives/hwpacks/wifibt/bluetooth.conf rootfs/etc/init
$ sudo cp archives/hwpacks/wifibt/bluetooth-ap6354.conf rootfs/etc/init

9. Setup serial console, booting as root user:

$ sudo sed -e 's/tty1/ttyS2/g' -e '/^exec/c exec /sbin/getty -a root -L 115200 ttyS2 vt100' < rootfs/etc/init/tty1.conf > ttyS2.conf
$ sudo mv ttyS2.conf rootfs/etc/init/ttyS2.conf

10. Setup the hostname:

$ echo Geekbox > hostname
$ sudo mv hostname rootfs/etc/hostname

Congratulations!
At this point, you have completed all the minimal-ubuntu images.
And so, all you should do is to burn these images down to device.


Download the images
1. Download the U-Boot first-level loader

$ upgrade_tool ul images/RK3368MiniLoaderAll_V2.40.bin

2. Download the parameter

$ upgrade_tool di -p utils/rockdev/parameter

3. Download the U-Boot second-level loader

$ upgrade_tool di uboot images/uboot.img
$ upgrade_tool di trust images/trust.img

4. Download the resource.img

$ upgrade_tool di resource images/resource.img

5. Download the ramfs.img

$ upgrade_tool di ramfs images/ramfs.img

6. Download the rootfs.img

$ upgrade_tool di linuxroot images/rootfs.img

7. Boot the device

$ upgrade_tool rd

Notice: root access is necessary if you haven't setup udev rules.
View our Wiki for more information: 
[url]http://forum.geekbox.tv/viewtopic.php?f=2&t=42[/url]




Graphic desktop environment
NOTE: The following commands need run on your Geekbox target!
1. Plug-in a cable, then setup the network:

[email protected]:~# echo auto eth0 > /etc/network/interfaces.d/eth0
[email protected]:~# echo iface eth0 inet dhcp >> /etc/network/interfaces.d/eth0
[email protected]:~# ln -fs /run/resolvconf/resolv.conf /etc/resolv.conf
[email protected]:~# ifup eth0

2. Extend the root partition:

[email protected]:~# resize2fs /dev/disk/by-label/linuxroot

Tips: the default volume size of root partition is specify in the first step of [Build the rootfs].


3. Install desktop packages

[email protected]:~# apt-get update
[email protected]:~# apt-get upgrade
[email protected]:~# apt-get install ubuntu-desktop

4. [Optional]For bad network environment, such as: China.
Backup the ubuntu deb packages:

[email protected]:~# apt-get install openssh-server
[email protected]:~# scp /var/cache/apt/archives/*.deb [email protected]:project/geekbox/ubuntu/archives/debs

If you did this, next time when you rebuilt the ubuntu system,
you can manually pull the deb packages into the apt debs archives path of target-device:

[email protected]:~# scp [email protected]:project/geekbox/ubuntu/archives/debs/*.deb  /var/cache/apt/archives/
[email protected]:~# apt-get update && apt-get upgrade && apt-get install ubuntu-desktop

This will save you a lot of time to download them from the website.


5. Reboot and enjoy your hard but challenging work

[email protected]:~# reboot

T.B.D.

1> ubuntu system depth optimization
2> Building the arm64 ubuntu system


References
1. <Miniroot>                       [url]http://androtab.info/miniroot/[/url]
2. <Ubuntu 14.04 LTS on Radxa>      [url]http://androtab.info/radxa_rock/ubuntu/[/url]
3. <Linaro rootfs on Radxa>         [url]http://wiki.radxa.com/Rock/ubuntu[/url]
4. <T-Chip Firefly-RK3288>          [url]http://wiki.t-firefly.com/index.php/Firefly-RK3288/en[/url]
5. <RootfsFromScratch>              [url]https://wiki.ubuntu.com/ARM/RootfsFromScratch[/url]
6. <rockchip mkbootimg>             [url]https://github.com/neo-technologies/rockchip-mkbootimg[/url]
7. <rkflashtool>                    [url]https://github.com/neo-technologies/rkflashtool.git[/url]
8. <initfamfs>                      [url]https://wiki.debian.org/initramfs[/url]
9. <Linux's Documentation>          [url]http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/ramfs-rootfs-initramfs.txt?id=HEAD[/url]