5. Ubuntu 根文件系统定制

以下基于 Ubuntu 18.04 64bit 根文件系统定制为例。

5.1. 准备工作

5.1.1. 安装 qemu

在 Linux PC 主机上安装模拟器:

sudo apt-get install qemu-user-static

5.1.2. 下载和解压 ubuntu-core

用户可以到 ubuntu cdimg 下载,选择下载 ubuntu-base-18.04.5-base-arm64.tar.gz

下载完之后,创建临时文件夹并解压根文件系统:

mkdir temp
sudo tar -xpf ubuntu-base-18.04.5-base-arm64.tar.gz -C temp

5.2. 修改根文件系统

5.2.1. 准备工作

准备网络:

sudo cp -b /etc/resolv.conf temp/etc/resolv.conf

准备 qemu:

sudo cp /usr/bin/qemu-aarch64-static temp/usr/bin/

创建一个挂载脚本,命名为 mount.sh,脚本内容如下:

#!/bin/bash
mnt() {
	echo "MOUNTING"
	sudo mount -t proc /proc ${2}proc
	sudo mount -t sysfs /sys ${2}sys
	sudo mount -o bind /dev ${2}dev
	sudo mount -o bind /dev/pts ${2}dev/pts
}
umnt() {
	echo "UNMOUNTING"
	sudo umount ${2}proc
	sudo umount ${2}sys
	sudo umount ${2}dev/pts
	sudo umount ${2}dev
}

if [ "$1" == "-m" ] && [ -n "$2" ] ;
then
	mnt $1 $2
elif [ "$1" == "-u" ] && [ -n "$2" ];
then
	umnt $1 $2
fi

添加执行权限并使用脚本进行挂载:

注意:稍后定制完成一定要记得取消挂载!!!

chmod +x mount.sh
./mount.sh -m temp/

进入根文件系统进行操作:

sudo chroot temp

5.2.2. 更新及安装

更新:

apt update
apt upgrade

至少需要安装一个 systemd,否则开机无法进入系统

apt install -y systemd

安装自己需要的功能

apt install vim git ....(根据自己需求添加)

安装 xubuntu:

apt-get install xubuntu-desktop

可能出现错误:

E: Unable to locate package xxxx

安装包的源没有添加到 /etc/apt/source.list 中,导致无法识别安装包,可以自行添加源,也可以使用下面给出的 source.list 覆盖原来的 /etc/apt/source.list 文件:

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb http://ports.ubuntu.com/ubuntu-ports/ bionic main restricted
deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://ports.ubuntu.com/ubuntu-ports/ bionic-updates main restricted
deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-updates main restricted

## Uncomment the following two lines to add software from the 'universe'
## repository.
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://ports.ubuntu.com/ubuntu-ports/ bionic universe
deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic universe
deb http://ports.ubuntu.com/ubuntu-ports/ bionic-updates universe
deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-updates universe

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://ports.ubuntu.com/ubuntu-ports/ bionic-backports main restricted
deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-backports main restricted

deb http://ports.ubuntu.com/ubuntu-ports/ bionic-security main restricted
deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-security main restricted
deb http://ports.ubuntu.com/ubuntu-ports/ bionic-security universe
deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-security universe
deb http://ports.ubuntu.com/ubuntu-ports/ bionic-security multiverse
deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-security multiverse

5.2.3. 添加用户及设置密码

添加用户:

useradd -s '/bin/bash' -m -G adm,sudo firefly

给用户设置密码:

passwd firefly

给root用户设置密码:

passwd root

修改完自己的根文件系统就可以退出了。

exit

一定要取消挂载:

./mount.sh -u temp/

5.3. 制作根文件系统

制作自己的根文件系统,大小依据自己的根文件系统而定,注意依据 temp 文件夹的大小来修改 count 值:

mkdir  rootfs
dd if=/dev/zero of=linuxroot.img bs=1M count=4000
mkfs.ext4 linuxroot.img
sudo mount linuxroot.img rootfs/
sudo cp -rfp temp/*  rootfs/
sudo umount rootfs/
e2fsck -p -f linuxroot.img
resize2fs  -M linuxroot.img

这样 linuxroot.img 就是最终的根文件系统映像文件了。

5.4. FAQs

5.4.1. 根文件系统加载后,大小不正常,未占满整个分区:

在系统正确加载后执行扩展文件系统命令:

resize2fs /dev/mtd/by-name/linuxroot