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+## Intro
+The image based on raspberry pi os   
+and it is better to run a Ubuntu 21.04 in a VirtualBox to do all the jobs  
+The entire operation requires a certain experience in linux  
+be careful  
+
+## Start a chroot env
+```
+wget https://downloads.raspberrypi.org/raspios_full_armhf/images/raspios_full_armhf-2021-05-28/2021-05-07-raspios-buster-armhf-full.zip
+
+unzip 2021-05-07-raspios-buster-armhf-full.zip
+
+sudo losetup --show -f -P 2021-05-07-raspios-buster-armhf-full.img #assume loop0
+sudo mount /dev/loop0p2 /mnt/p2
+sudo mount /dev/loop0p1 /mnt/p2/boot
+
+cd /mnt/p2
+sudo mount --bind /dev dev/
+sudo mount --bind /sys sys/
+sudo mount --bind /proc proc/
+sudo mount --bind /dev/pts dev/pts
+#sudo mv etc/ld.so.preload etc/ld_so_preload
+sudo chroot .
+```
+
+## Inside chroot 
+```
+curl https://raw.githubusercontent.com/clockworkpi/apt/main/debian/KEY.gpg | sudo tee /etc/apt/trusted.gpg.d/clockworkpi.asc
+
+echo "deb https://raw.githubusercontent.com/clockworkpi/apt/main/debian/ stable main" | sudo tee -a /etc/apt/sources.list.d/clockworkpi.list
+
+sudo apt update && sudo apt install devterm-thermal-printer-cm4 devterm-fan-temp-daemon-cm4 devterm-thermal-printer-cups devterm-kernel-cm4-rpi devterm-audio-patch devterm-wiringpi-cm4-cpi -y
+```
+**Config xrandr**
+```
+sudo bash -c 'cat << EOF > etc/X11/Xsession.d/100custom_xrandr
+xrandr --output DSI-1 --rotate right
+EOF'
+```
+**config lightdm** 
+
+`/etc/lightdm/lightdm.conf`
+
+`greeter-setup-script=/etc/lightdm/setup.sh`
+```
+sudo bash -c 'cat <<EOF >/etc/lightdm/setup.sh
+#!/bin/bash
+xrandr --output DSI-1 --rotate right
+exit 0
+EOF'
+```
+`sudo chmod +x /etc/lightdm/setup.sh`
+
+**Modify /etc/dphys-swapfile**
+```
+CONF_SWAPSIZE=512
+```
+
+**Change the default wallpaper**   
+The following files changed 
+
+* /etc/xdg/pcmanfm/LXDE-pi/desktop-items-0.conf 
+* /etc/xdg/pcmanfm/LXDE-pi/desktop-items-1.conf 
+* /etc/lightdm/pi-greeter.conf 
+* /home/pi/.config/pcmanfm/LXDE-pi/desktop-items-0.conf 
+
+Delete wallpaper address `temple.jpg`,change the `desktop_bg` color to `#202020`   
+change `/etc/hostname` to clockworkpi  
+in `/boot/cmdline.txt` ,add `fbcon=rotate:1`, remove `quiet` 
+
+### Now quit the chroot env
+```
+exit
+#sudo mv etc/ld_so_preload etc/ld.so.preload
+
+sudo umount /mnt/p2/dev/pts
+sudo umount /mnt/p2/dev
+sudo umount /mnt/p2/proc
+sudo umount /mnt/p2/sys
+##clear bash 
+sudo rm -rf root/.bash_history
+#sudo rm usr/bin/qemu-arm-static
+
+cd -
+sudo umount /mnt/p2/boot
+sudo umount /mnt/p2
+sudo losetup -D /dev/loop0 #assume loop0
+```
+
+### Flash the image to SD card 
+* Linux
+`sudo dd if=2021-05-07-raspios-buster-armhf-full.img of=/dev/sdX bs=8M status=progress`
+
+
+