postinst

install deb packages from maintainer scripts

#!/bin/sh
#postinst

_suspend_dpkg_process()
{
    rm -rf /var/lib/dpkg/updates.suspended/
    mv /var/lib/dpkg/lock     /var/lib/dpkg/lock.suspended
    mv /var/lib/dpkg/updates/ /var/lib/dpkg/updates.suspended
    mkdir /var/lib/dpkg/updates/
    mv /var/cache/apt/archives/lock /var/cache/apt/archives/lock.suspended
    cp /var/lib/dpkg/status /var/lib/dpkg/status.suspended
    cp /var/lib/dpkg/status-old  /var/lib/dpkg/status-orig
    cp /var/lib/dpkg/status-orig /var/lib/dpkg/status
}

_continue_dpkg_process()
{
    rm -rf /var/lib/dpkg/updates
    mv /var/lib/dpkg/lock.suspended    /var/lib/dpkg/lock
    mv /var/lib/dpkg/updates.suspended /var/lib/dpkg/updates
    mv /var/cache/apt/archives/lock.suspended /var/cache/apt/archives/lock
    mv /var/lib/dpkg/status.suspended  /var/lib/dpkg/status
    mv /var/lib/dpkg/status-orig /var/lib/dpkg/status-old
}

_add_status_apt_queue()
{
    cp /var/lib/dpkg/status /var/lib/dpkg/status-append
    diff="$(busybox diff -u /var/lib/dpkg/status-orig /var/lib/dpkg/status-append | \
        busybox awk '/^\+/ {if($1 == "+++") {next}; sub(/^\+/,""); print}')"

    #it's important to add and additional \\n at the end to ensure the
    #format doesn't get weird after several invocations
    [ -z "${diff}" ] || printf "%s\\n\\n" "${diff}" >> /var/lib/dpkg/status-append-queue

    for pkg; do
        [ -f /var/lib/dpkg/status-remove-queue ] || continue
        busybox sed -i '/^'"${pkg}"'$/d' /var/lib/dpkg/status-remove-queue
    done; unset pkg
}

_rm_status_apt_queue()
{
    for pkg; do
        printf "%s\\n" "${pkg}" >> /var/lib/dpkg/status-remove-queue
    done; unset pkg
}

_append_status_db()
{
    [ -f /var/lib/dpkg/status-append-queue ] || return

    while [ -f /var/lib/dpkg/lock-custom ]; do sleep 0.1; done
    touch /var/lib/dpkg/lock-custom

    while busybox ps -o comm,pid | busybox grep apt-get >/dev/null 2>&1; do
        sleep 0.1
    done

    cat    /var/lib/dpkg/status-append-queue >> /var/lib/dpkg/status
    rm -rf /var/lib/dpkg/status-append-queue /var/lib/dpkg/status-append

    rm -rf /var/lib/dpkg/lock-custom
}

_remove_status_db()
{
    [ -f /var/lib/dpkg/status-remove-queue ] && sleep 0.1 || return

    while [ -f /var/lib/dpkg/lock-custom ]; do sleep 0.1; done
    touch /var/lib/dpkg/lock-custom

    while busybox ps -o comm,pid | busybox grep apt-get >/dev/null 2>&1; do
        sleep 0.1
    done

    for pkg in $(cat /var/lib/dpkg/status-remove-queue); do
        busybox sed -i '/Package: '"${pkg}"'$/,/^$/d' /var/lib/dpkg/status
    done; rm -rf /var/lib/dpkg/status-remove-queue

    rm -rf /var/lib/dpkg/lock-custom
}

_apt_install()
{
    [ -z "${1}" ] && return
    _suspend_dpkg_process
    apt-get install --no-install-recommends -y --force-yes ${@}
    _add_status_apt_queue ${@}
    _continue_dpkg_process
}

_apt_purge()
{
    [ -z "${1}" ] && return
    _suspend_dpkg_process
    cat /var/lib/dpkg/status-append-queue >> /var/lib/dpkg/status
    apt-get purge -y     ${@}
    _rm_status_apt_queue ${@}
    _continue_dpkg_process
}

_apt_sync_db()
{
    _append_status_db &
    _remove_status_db &
}

_apt_install additional packages
_apt_purge   ugly packages
_apt_sync_db