Raspberry Pi CM4(3): Customizing your own Raspberry Pi image

1. Mirror downloads

Use the latest Raspberry Pi image, Raspberry Pi OS Lite, kernel version 6.6.
download link

/raspios_lite_arm64/images/raspios_lite_arm64-2024-07-04/

2. Mount the image to ubuntu

The Raspberry Pi image downloaded in the previous step
```
jun@ubuntu:$ ls
```
View the first unused loopback device
```
jun@ubuntu:$ losetup -f
/dev/loop0
```

Associating a Raspberry Pi image to a loopback device

jun@ubuntu:$ sudo losetup /dev/loop0  
[sudo] password for jun:

Viewing the partitions, two zones are detected, the smaller of which is the system partition and the larger is the root filesystem

jun@ubuntu:$ sudo kpartx -av /dev/loop0
add map loop0p1 (253:0): 0 1048576 linear 7:0 8192
add map loop0p2 (253:1): 0 4481024 linear 7:0 1056768

Creating a system partition mount directory
```
jun@ubuntu:$ mkdir boot
```
Creating a root filesystem mount directory
```
jun@ubuntu:$ mkdir rootfs
```

Mounting the system partition

jun@ubuntu:$ sudo mount /dev/mapper/loop0p1 ./boot/

Mounting the root filesystem

jun@ubuntu:$ sudo mount /dev/mapper/loop0p2 ./rootfs/

Viewing the system partition

jun@ubuntu:ig210$ ls ./boot/
                    fixup_x.dat                 start_x.elf
                          initramfs_2712     
                     fixup_cd.dat  initramfs8       overlays          start_cd.elf
                                     start_db.elf
              fixup_db.dat  kernel_2712.img

Viewing the Root File System

jun@ubuntu:ig210$ ls ./rootfs/
bin  boot  dev  etc  home  lib  lost+found  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var

3. Customized system configuration

3.1 Enabling the Debug Serial Port

Modify the system partition under the
```
$ cd boot/
boot$ sudo vi 
```
existand add the following at the end of the
```
enable_uart=1
```

3.2 Setting the user name and password

Set the username tojunThe password is9

Execute the following command in a Raspberry Pi that is already in a terminal to get the ciphertext of the password, as follows to set the password as9

root@jun:/home/jun# echo 9 | openssl passwd -6 -stdin
$6$tSX0UC/$gqnju1u.BPjPLz1659xUok2GHViNBdcW7D4o4g4tf9xlbVFn4SU2EaV3/0Q02yquTkluWdZBi8sKrB0n3vtaC/

Splicing username and ciphertext

jun:$6$tSX0UC/$gqnju1u.BPjPLz1659xUok2GHViNBdcW7D4o4g4tf9xlbVFn4SU2EaV3/0Q02yquTkluWdZBi8sKrB0n3vtaC/

Write the splice string obtained in the previous step to the boot partition'sPapers

3.3 Setting the hostname

Modify the root filesystem under thehostname, change the hostname tojun
```
sudo vi rootfs/etc/hostname
```
Modify the root filesystem under thehostsfile, which will127.0.1.1The corresponding hostname is also changed tojun

3.4 Enabling SSH

existbootCreate an empty file in the partitionSSHcan immediately (do sth)
```
boot$ sudo touch SSH
```

3.5 Enabling the IIC

modificationsboot/, canceleddtparam=i2c_arm=oncomment that adds thedtparam=i2c_vc=on
modificationsrootfs/etc/modules, add a linei2c-dev
```
jun@ubuntu:$ sudo vi rootfs/etc/modules
```

3.6 Enabling SPI

modificationsboot/, canceled#dtparam=spi=onIf you don't have it, add it.

3.7 Enabling All Serial Ports

modificationsboot/, add the following

deoverlay=uart0,txd0_pin=14,rxd0_pin=15
dtoverlay=uart2,txd2_pin=0,rxd2_pin=1
dtoverlay=uart3,txd3_pin=4,rxd3_pin=5
dtoverlay=uart4,txd4_pin=8,rxd4_pin=9
dtoverlay=uart5,txd5_pin_12,rxd5_pin=13

3.8 Adding Logo

Show Logo when user logs in
utilizationfigletThis tool generates point and line diagrams

existrootfs/etc/profileAt the end of the document addechoCommand, Print Dot Line Logo

jun@ubuntu:rootfs$ sudo vi etc/profile

echo -e "\033[0;32m
 _____   _____   ____    _____ 
|_   _| | ____| / ___|  |_   _|
  | |   |  _|   \___ \    | |  
  | |   | |___   ___) |   | |  
  |_|   |_____| |____/    |_|  
                                                                        
\033[0m\n"

4. Unmount the image

jun@ubuntu:$ ls
  boot  rootfs
jun@ubuntu:$ sudo umount ./boot 
jun@ubuntu:$ sudo umount ./rootfs
jun@ubuntu:$ sudo losetup -d /dev/loop0

5. Mirror burning

see documentRaspberry Pi CM4(I): Mirror Burning.