Mini Shell

#!/bin/bash
# -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
# ex: ts=8 sw=4 sts=4 et filetype=sh

COMMAND="$1"
KERNEL_VERSION="$2"
BOOT_DIR_ABS="$3"
KERNEL_IMAGE="$4"

if ! [[ $KERNEL_INSTALL_MACHINE_ID ]]; then
    exit 0
fi

if ! [[ -d "$BOOT_DIR_ABS" ]]; then
    exit 0
fi

MACHINE_ID=$KERNEL_INSTALL_MACHINE_ID

BOOT_DIR="/$MACHINE_ID/$KERNEL_VERSION"
BOOT_ROOT=${BOOT_DIR_ABS%$BOOT_DIR}
LOADER_ENTRY="$BOOT_ROOT/loader/entries/$MACHINE_ID-$KERNEL_VERSION.conf"

if [[ $COMMAND == remove ]]; then
    exec rm -f "$LOADER_ENTRY"
fi

if ! [[ $COMMAND == add ]]; then
    exit 1
fi

if ! [[ $KERNEL_IMAGE ]]; then
    exit 1
fi

if [[ -f /etc/os-release ]]; then
    . /etc/os-release
elif [[ -f /usr/lib/os-release ]]; then
    . /usr/lib/os-release
fi

if ! [[ $PRETTY_NAME ]]; then
    PRETTY_NAME="Linux $KERNEL_VERSION"
fi

if [[ -f /etc/kernel/cmdline ]]; then
    read -r -d '' -a BOOT_OPTIONS < /etc/kernel/cmdline
elif [[ -f /usr/lib/kernel/cmdline ]]; then
    read -r -d '' -a BOOT_OPTIONS < /usr/lib/kernel/cmdline
else
    declare -a BOOT_OPTIONS

    read -r -d '' -a line < /proc/cmdline
    for i in "${line[@]}"; do
        [[ "${i#initrd=*}" != "$i" ]] && continue
        BOOT_OPTIONS+=("$i")
    done
fi

cp "$KERNEL_IMAGE" "$BOOT_DIR_ABS/linux" &&
   chown root:root "$BOOT_DIR_ABS/linux" &&
   chmod 0644 "$BOOT_DIR_ABS/linux" || {
    echo "Could not copy '$KERNEL_IMAGE to '$BOOT_DIR_ABS/linux'." >&2
    exit 1
}

mkdir -p "${LOADER_ENTRY%/*}" || {
    echo "Could not create loader entry directory '${LOADER_ENTRY%/*}'." >&2
    exit 1
}

{
    echo "title      $PRETTY_NAME"
    echo "version    $KERNEL_VERSION"
    echo "machine-id $MACHINE_ID"
    echo "options    ${BOOT_OPTIONS[*]}"
    echo "linux      $BOOT_DIR/linux"
    [[ -f $BOOT_DIR_ABS/initrd ]] && \
        echo "initrd     $BOOT_DIR/initrd"
    :
} > "$LOADER_ENTRY" || {
    echo "Could not create loader entry '$LOADER_ENTRY'." >&2
    exit 1
}
exit 0