HOWTO: Upgrade Raspberry Pi OS from bullseye to bookworm

pi-dist-upgrade.sh

### WARNING: READ CAREFULLY BEFORE ATTEMPTING ###
#
# Credit to anfractuosity and fgimenezm for figuring out additional details for kernels
#

# Make sure everything is up-to-date
sudo apt update && sudo apt -y dist-upgrade && sudo apt -y autoremove && sudo apt -y clean

# Reboot once to ensure the running state uses the latest of everything.
sudo reboot

# Change all repos from bullseye to bookworm 
sudo sed -i -e 's/bullseye/bookworm/g' /etc/apt/sources.list /etc/apt/sources.list.d/*.list

cat <<_ENDL
### Check contents of /etc/apt/sources.list against below:
deb http://deb.debian.org/debian bookworm main contrib non-free non-free-firmware
deb http://security.debian.org/debian-security bookworm-security main contrib non-free non-free-firmware
deb http://deb.debian.org/debian bookworm-updates main contrib non-free non-free-firmware
# Uncomment deb-src lines below then 'apt-get update' to enable 'apt-get source'
#deb-src http://deb.debian.org/debian bookworm main contrib non-free
#deb-src http://security.debian.org/debian-security bookworm-security main contrib non-free
#deb-src http://deb.debian.org/debian bookworm-updates main contrib non-free

### Check contents of /etc/apt/sources.list.d/raspi.list against below:
deb http://archive.raspberrypi.org/debian/ bookworm main
# Uncomment line below then 'apt-get update' to enable 'apt-get source'
#deb-src http://archive.raspberrypi.org/debian/ bookworm main
_ENDL

# Do actual update
sudo apt update && sudo apt -y full-upgrade && sudo apt -y clean && sudo apt -y autoremove

# Reboot, but can be delayed till after bootloader and kernel update
sudo reboot

# Remove old config files after doing sanity checks
sudo apt purge ?config-files

### Switch to the new kernels ###
# Prep
sudo dpkg --purge --force-depends raspberrypi-kernel raspberrypi-bootloader
sudo umount /boot
sudo fsck -y /boot
sudo mkdir /boot/firmware
sudo sed -i.bak -e "s#boot#boot/firmware#" /etc/fstab
sudo systemctl daemon-reload
sudo mount /boot/firmware

## DO NOT RESTART ANY SERVICES WHEN PROMPTED - systemd is in poor state till pi restarts.
sudo apt install raspi-firmware

# Actually install the kernels. Make sure you pick the right version for your Pi
# sudo apt install linux-image-rpi-v8 linux-headers-rpi-v8      # 64bit
# sudo apt install linux-image-rpi-v7l linux-headers-rpi-v7l    # 32bit
# sudo apt install linux-image-rpi-v6 linux-headers-rpi-v6      

# Append auto_initramfs=1 to the bottom of file where it says [all]
sudo sed -i.bak '$ a\auto_initramfs=1' /boot/firmware/config.txt 

# Reboot
sudo reboot

# Verify using "uname -a" (correct as of 10/2023)
# Old kernel
# Linux raspberrypi 6.1.21-v8+ #1642 SMP PREEMPT Mon Apr  3 17:24:16 BST 2023 aarch64 GNU/Linux
# New kernel
# Linux raspberrypi 6.1.0-rpi4-rpi-v8 #1 SMP PREEMPT Debian 1:6.1.54-1+rpt2 (2023-10-05) aarch64 GNU/Linux

# If you are not converted to using NetworkManager, you might lose networking upon reboot. 
# Check the ARP table to see what the new DHCP assigned IP address is. You may have to manually set the IP address again
# Thanks to solsticedhiver for identifying this
#
# Install NetworkManager if not already installed
sudo apt-get install --no-install-recommends network-manager
#
# Switch to NetworkManager from dhcpcd
sudo systemctl enable --now NetworkManager
sudo systemctl disable --now dhcpcd
#
# Set up static IP. Adjust as necessary 
sudo nmcli -p connection show 
sudo nmcli -p connection show "Wired connection 1"
sudo nmcli con mod "Wired connection 1" ipv4.method manual ipv4.addresses 192.168.1.5/24 ipv4.gateway 192.168.1.1

# Set up a new WiFi connection:
# sudo nmcli con add type wifi con-name MFSL ssid MFSL wifi-sec.key-mgmt wpa-psk wifi-sec.psk MixedFruitS@l@d save yes

# Remove obsolete link to service file left by aspberrypi-net-mods of bullseye , removed in bookworm.
# Ref: https://github.com/RPi-Distro/raspberrypi-net-mods/
sudo rm -f /etc/systemd/system/multi-user.target.wants/raspberrypi-net-mods.service

# Reboot
sudo reboot

#
# Bonus steps
#

# Check packages not installed from bookworm release repositories (any source)
dpkg --get-selections |awk '{print $1}'| \
        xargs -rn9 bash -c 'apt show $0 "$@" 2>/dev/null| \
        grep -E "^Package|^APT-"' | grep -v " bookworm" |grep -B2 '^APT-Sources:'

# Install btop
sudo apt-get install btop

cat <<_ENDL
# Update /etc/ssh/sshd_config for up to date, secure by default config. Use ssh-audit to verify
KexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org
HostKeyAlgorithms ssh-ed25519-cert-v01@openssh.com,ssh-ed25519
Ciphers chacha20-poly1305@openssh.com
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com
_ENDL

Minor QOL updates to fork

• Added warning comment
• Added check for non-bookworm packages.

• Added cleanup for a link to removed systemd unit of raspberrypi-net-mods (obsoleted by NetworkManager transition, and removed in the bookworm version of the package)