#!/bin/bash
#----------------------------------------------------------------------------
# /usr/libexec/update-initrd-images - create new set of initrd images
#
# Copyright (c) 2001-2023 the eisfair team, team(at)eisfar(dot)org
#
# Creation   : 2021-02-20 dv
# Last Update: 2021-03-13 16:28:02 dv
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# check if space is sufficient to activate new kernel
# old initrd has to be replaced by new one. If the new one is larger than
# the old one, than we have to check for available disk space in /boot
#-----------------------------------------------------------------------------
check_for_sufficient_disk_space()
{
    local kernel="${1}"

    local new_size=$(du "/var/lib/alt-kernel/initrd-${kernel}.gz" | awk '{print $1}')
    local old_size=$(du "/boot/initrd-${kernel}.gz" | awk '{print $1}')

    if [ "${new_size:-0}" -gt "${old_size:-0}" ]
    then
        local available_space=0

        if [ -n "$(df /boot | grep ' /boot$')" ]
        then
            set -- $(df /boot | grep ' /boot$')
            available_space="${4}"
        else
            set -- "$(df / | grep ' /')"
            available_space="${4}"
        fi

        local needed_space=$((${new_size:-0} - ${old_size:-0}))

        if [ "${needed_space}" -gt "${available_space}" ]
        then
            # insufficient space
            return 1
        fi
    fi

    return 0
}

#-----------------------------------------------------------------------------
# deactivate the oldest kernel (if possible)
#-----------------------------------------------------------------------------
deactivate_oldest_kernel()
{
    local current_kernel="${1}"
    local kernel_list="${2}"
    local running_kernel="$(uname -r)"

    local kernel
    for kernel in ${kernel_list}
    do
        if [ "${kernel}" = "${current_kernel}" ]
        then
            # end of list reached
            return 1
        fi

        if [ "${kernel}" != "${running_kernel}" ] &&
           [ -f "/boot/kernel-${kernel}" ]        &&
           [ -f "/boot/initrd-${kernel}.gz" ]
        then
            local fix_link=false

            if [ "$(basename $(readlink /boot/kernel))" = "kernel-${kernel}" ]
            then
                fix_link=true
            fi

            rm -f "/var/lib/alt-kernel/kernel-${kernel}"
            rm -f "/var/lib/alt-kernel/initrd-${kernel}.gz"

            mv "/boot/kernel-${kernel}"    \
                "/var/lib/alt-kernel/kernel-${kernel}"
            mv "/boot/initrd-${kernel}.gz" \
                "/var/lib/alt-kernel/initrd-${kernel}.gz"

            if [ "${fix_link}" = true ]
            then
                rm -f /boot/kernel
                rm -f /boot/initrd.gz

                kernels=$(ls /boot/kernel-* | sort -Vr)

                for next_kernel in ${kernels}
                do
                    next_version="$(basename ${next_kernel} | sed 's#kernel-##g')"
                    next_initrd="/boot/initrd-${next_version}.gz"
                    if [ -f "${next_initrd}" ]
                    then
                        ln -sr "${next_kernel}" /boot/kernel
                        ln -sr "${next_initrd}" /boot/initrd.gz
                        break
                    fi
                done
            fi

            return 0
        fi
    done

    return 1
}

#-----------------------------------------------------------------------------
# main program
#-----------------------------------------------------------------------------
main()
{
    # list of kernel (newest first)
    local kernel_reverse_list=$(ls /lib/modules | sort -rV)

    # list of kernels (oldest first)
    local kernel_forward_list=$(ls /lib/modules | sort -V)

    # recreate initrd files for kernels
    local kernel
    for kernel in ${kernel_reverse_list}
    do
        mkinitrd --force -q /var/lib/alt-kernel/initrd-${kernel}.gz ${kernel}
        if [ -f "/boot/initrd-${kernel}.gz" ]
        then
            if ! check_for_sufficient_disk_space "${kernel}"
            then
                if deactivate_oldest_kernel "${kernel}" "${kernel_forward_list}"
                then
                    # move initrd to boot
                    rm -f /boot/initrd-${kernel}.gz
                    mv /var/lib/alt-kernel/initrd-${kernel}.gz /boot/initrd-${kernel}.gz
                fi
            else
                # move initrd to boot
                rm -f /boot/initrd-${kernel}.gz
                mv /var/lib/alt-kernel/initrd-${kernel}.gz /boot/initrd-${kernel}.gz
            fi
        fi
    done
}

main "${@}"