适用于RK3568，亲测有效
1、下载ARM64根文件系统 ubuntu-base-18.04.5-base-arm64.tar.gz
http://cdimage.ubuntu.com/ubuntu-base/releases/18.04/release/
mkdir ubuntu_rootfs
tax xvf ubuntu-base-18.04.5-base-arm64.tar.gz -C ubuntu_rootfs
2、进入base系统
mount -t proc /proc ./ubuntu_rootfs/proc
mount -t sysfs /sys ./ubuntu_rootfs/sys
mount -o bind /dev ./ubuntu_rootfs/dev
mount -o bind /dev/pts ./ubuntu_rootfs/dev/pts
chroot ubuntu_rootfs
echo “nameserver 114.114.114.114” > /etc/resolv.conf
3、修改下载源
/etc/apt/source.list，修改内容如下
deb http://mirrors.huaweicloud.com/ubuntu-ports/ bionic main multiverse restricted universe
deb http://mirrors.huaweicloud.com/ubuntu-ports/ bionic-backports main multiverse restricted universe
deb http://mirrors.huaweicloud.com/ubuntu-ports/ bionic-proposed main multiverse restricted universe
deb http://mirrors.huaweicloud.com/ubuntu-ports/ bionic-security main multiverse restricted universe
deb http://mirrors.huaweicloud.com/ubuntu-ports/ bionic-updates main multiverse restricted universe
deb-src http://mirrors.huaweicloud.com/ubuntu-ports/ bionic main multiverse restricted universe
deb-src http://mirrors.huaweicloud.com/ubuntu-ports/ bionic-backports main multiverse restricted universe
deb-src http://mirrors.huaweicloud.com/ubuntu-ports/ bionic-proposed main multiverse restricted universe
deb-src http://mirrors.huaweicloud.com/ubuntu-ports/ bionic-security main multiverse restricted universe
deb-src http://mirrors.huaweicloud.com/ubuntu-ports/ bionic-updates main multiverse restricted universe4、安装桌面系统
apt-get update
apt install net-tools #ifconfig
apt-get install inetutils-ping #ping
apt-get install language-pack-en-base sudo ssh net-tools ethtool wireless-tools ifupdown network-manager iputils-ping rsyslog bash-completion htop
apt-get install ubuntu-desktop
5、制作根文件系统
dd if=/dev/zero of=linuxroot.img bs=1M count=1024
mkfs.ext4 linuxroot.img
mkdir hyrootfs
mount linuxroot.img hyrootfs/
cp -rfp ubuntu_rootfs/* hyrootfs/
umount hyrootfs/
e2fsck -p -f linuxroot.img
resize2fs -M linuxroot.img