update-kernel.sh.in

#!/bin/bash
#
# Copyright (c) 2018 Mateusz Marzantowicz
#
# SPDX-License-Identifier: MIT

set -euo pipefail
shopt -s extglob

readonly CONFIG=
readonly KERNEL_PACKAGE=
readonly VERSION=

BOOTABLE_DEVICES=()

# Read configuration file
[[ -f ${CONFIG} ]] && {
    . ${CONFIG}
}

m4_include(color.sh)
m4_include(messages.sh)

# Return path of kernel image
kernel_image() {
    printf '/boot/vmlinuz-%s' "$1"
}

# Return path of initial ramdisk
initrd_image() {
    printf '/boot/initramfs-%s.img' "$1"
}

# Copy initial ramdisk file(s) to destination device
install_initrd() {
    local -r initrd=$1; shift
    local -r dest=$1

    msg "Installing initial ramdisk '${initrd}' on '${dest}'"

    cp "$initrd" "$dest" &>/dev/null || {
        error "Could not copy initial ramdisk to '$dest'"
        return 1
    }
}

# Copy kernel file(s) to destination device
install_kernel() {
    local -r kernel=$1; shift
    local -r dest=$1

    msg "Installing kernel image '${kernel}' on '${dest}'"

    cp "$kernel" "$dest" &>/dev/null || {
        error "Could not copy kernel image to '$dest'"
        return 1
    }
}

# See if kernel package is installed
is_installed() {
    local -r pkg=$1

    pacman -Qq "$pkg" &>/dev/null || {
        error "Kernel package '$pkg' is not installed"
        return 1
    }
}

# Update kernel and initial ramdisk on each bootable device
update_kernel() {
    local -r kernel=$1
    local device

    for device in "${BOOTABLE_DEVICES[@]}"; do
        verify_destination "$device" && {
            install_kernel "$( kernel_image "$kernel" )" "$device"
            install_initrd "$( initrd_image "$kernel" )" "$device"
        }
    done

    return 0
}

# Check path is a valid destination device for kernel and initrd files
verify_destination() {
    local -r dest=$1

    [[ -d $dest ]] || {
        error "'$dest' is not a directory. Skipping device."
        return 1
    }

    mountpoint -q "$dest" || {
        error "'$dest' is not a mountpoint. Skipping device."
        return 1
    }

    [[ -w $dest ]] || {
        error "'$dest' is not writable. Skipping device."
        return 1
    }

    return 0
}

# Main: start here
main() {
    enable_colors

    case "$1" in
        @($KERNEL_PACKAGE)) is_installed "$1" && update_kernel "$1" ;;
        *) error "Invalid kernel package '$1' specified."; exit 1 ;;
    esac
}

main "$@" && exit 0

# vim: set ft=sh ts=4 sw=4 et: