rpi-copy-boot

#!/bin/sh

set -eu

PROGNAME=$(basename $0)
BASEDIR=$(cd $(dirname $0); pwd)

error() {
    echo "$1" >&2
    exit 1
}

help() {
    cat <<EOF >&2
Usage: $PROGNAME [options] <RPI> <KVER> <TFTPROOT>

Help Options:
  -h, --help

Arguments:
  <RPI>
    Hostname of the target Raspberry Pi which can be accessed using SSH

  <KVER>
    Kernel version like 4.19.58-v7+

  <TFTPROOT>
    TFTP root folder containing boot files

Descripion:
  This script performs:

    1. Updating initrd.img
    2. Reading the serial number from /proc/cpuinfo
    3. Renaming the old boot folder to SERNO.backup.\$(date +%Y%m%d%H%M%S)
    4. Creating a new boot folder named as the last 8 octet characters in the
       serial number
    5. Recursively copying files in /boot on the target Raspberry Pi into the
       new boot folder

  After that, it may be necessary to update the following files by hand:

    * cmdline.txt
    * config.txt

Examples:
  \$ $PROGNAME rpi 4.19.58-v7+ /Volumes/pxeboot/tftproot
EOF
    exit 0
}

while [ $# -gt 0 ]
do
    case "$1" in
        '-h' | '--help')
            help
            ;;
        *)
            break
            ;;
    esac
done

RPI="$1"
KVER="$2"
TFTPROOT="$3"

if [ -z "$RPI" ]; then
    error "RPI is required"
fi

if [ -z "$KVER" ]; then
    error "KVER is required"
fi

if [ -z "$TFTPROOT" ]; then
    error "TFTPROOT is required"
fi

ssh $RPI sudo rm /boot/initrd.img-*
ssh $RPI sudo update-initramfs -v -k $KVER -c

SERNO=$(ssh $RPI cat /proc/cpuinfo | grep Serial | cut -d ':' -f2 | \
        rev | cut -c 1-8 | rev)

if [ -e "$TFTPROOT/$SERNO" ]; then
    mv "$TFTPROOT/$SERNO" "$TFTPROOT/$SERNO.backup.$(date +%Y%m%d%H%M%S)"
fi
mkdir -p $TFTPROOT/$SERNO

scp -r $RPI:/boot/* $TFTPROOT/$SERNO/