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File name : cloud-init-generator
Content :
#!/bin/sh
set -f

LOG=""
DEBUG_LEVEL=1
LOG_D="/run/cloud-init"
LOG_F="/run/cloud-init/cloud-init-generator.log"
ENABLE="enabled"
DISABLE="disabled"
RUN_ENABLED_FILE="$LOG_D/$ENABLE"
RUN_DISABLED_FILE="$LOG_D/$DISABLE"
CLOUD_TARGET_NAME="cloud-init.target"
# lxc sets 'container', but lets make that explicitly a global
CONTAINER="${container}"

# start: template section
CLOUD_SYSTEM_TARGET="/lib/systemd/system/cloud-init.target"
    dsidentify="/usr/lib/cloud-init/ds-identify"
# end: template section

debug() {
    local lvl="$1"
    shift
    [ "$lvl" -gt "$DEBUG_LEVEL" ] && return
    if [ -z "$LOG" ]; then
        { [ -d "$LOG_D" ] || mkdir -p "$LOG_D"; } &&
            { : > "$LOG_F"; } >/dev/null 2>&1 && LOG="$LOG_F" ||
            LOG="/dev/kmsg"
    fi
    echo "$@" >> "$LOG"
}

etc_file() {
    local pprefix="${1:-/etc/cloud/cloud-init.}"
    _RET="unset"
    [ -f "${pprefix}$ENABLE" ] && _RET="$ENABLE" && return 0
    [ -f "${pprefix}$DISABLE" ] && _RET="$DISABLE" && return 0
    return 0
}

read_proc_cmdline() {
    # return /proc/cmdline for non-container, and /proc/1/cmdline for container
    local ctname="systemd"
    if [ -n "$CONTAINER" ] && ctname=$CONTAINER ||
        systemd-detect-virt --container --quiet; then
        if { _RET=$(tr '\0' ' ' < /proc/1/cmdline); } 2>/dev/null; then
            _RET_MSG="container[$ctname]: pid 1 cmdline"
            return
        fi
        _RET=""
        _RET_MSG="container[$ctname]: pid 1 cmdline not available"
        return 0
    fi

    _RET_MSG="/proc/cmdline"
    read _RET < /proc/cmdline
}

kernel_cmdline() {
    local cmdline="" tok=""
    if [ -n "${KERNEL_CMDLINE+x}" ]; then
        # use KERNEL_CMDLINE if present in environment even if empty
        cmdline=${KERNEL_CMDLINE}
        debug 1 "kernel command line from env KERNEL_CMDLINE: $cmdline"
    else
        read_proc_cmdline && cmdline="$_RET" &&
                debug 1 "kernel command line ($_RET_MSG): $cmdline"
    fi
    _RET="unset"
    cmdline=" $cmdline "
    tok=${cmdline##* cloud-init=}
    [ "$tok" = "$cmdline" ] && _RET="unset"
    tok=${tok%% *}
    [ "$tok" = "$ENABLE" -o "$tok" = "$DISABLE" ] && _RET="$tok"
    return 0
}

default() {
    _RET="$ENABLE"
}

check_for_datasource() {
    local ds_rc=""
    if [ ! -x "$dsidentify" ]; then
        debug 1 "no ds-identify in $dsidentify"
        return 0
    fi
    $dsidentify
    ds_rc=$?
    debug 1 "ds-identify rc=$ds_rc"
    if [ "$ds_rc" = "0" ]; then
        return 0
    fi
    return 1
}

main() {
    local normal_d="$1" early_d="$2" late_d="$3"
    local target_name="multi-user.target" gen_d="$early_d"
    local link_path="$gen_d/${target_name}.wants/${CLOUD_TARGET_NAME}"
    local ds=""

    debug 1 "$0 normal=$normal_d early=$early_d late=$late_d"
    debug 2 "$0 $*"

    local search result="error" ret=""
    for search in kernel_cmdline etc_file default; do
        if $search; then
            debug 1 "$search found $_RET"
            [ "$_RET" = "$ENABLE" -o "$_RET" = "$DISABLE" ] &&
                result=$_RET && break
        else
            ret=$?
            debug 0 "search $search returned $ret"
        fi
    done

    # enable AND ds=found == enable
    # enable AND ds=notfound == disable
    # disable || <any> == disabled
    if [ "$result" = "$ENABLE" ]; then
        debug 1 "checking for datasource"
        check_for_datasource
        ds=$?
        if [ "$ds" = "1" ]; then
            debug 1 "cloud-init is enabled but no datasource found, disabling"
            result="$DISABLE"
        fi
    fi

    if [ "$result" = "$ENABLE" ]; then
        if [ -e "$link_path" ]; then
                debug 1 "already enabled: no change needed"
        else
            [ -d "${link_path%/*}" ] || mkdir -p "${link_path%/*}" ||
                debug 0 "failed to make dir $link_path"
            if ln -snf "$CLOUD_SYSTEM_TARGET" "$link_path"; then
                debug 1 "enabled via $link_path -> $CLOUD_SYSTEM_TARGET"
            else
                ret=$?
                debug 0 "[$ret] enable failed:" \
                    "ln $CLOUD_SYSTEM_TARGET $link_path"
            fi
        fi
        if [ -e $RUN_DISABLED_FILE ]; then
            debug 1 "removing $RUN_DISABLED_FILE and creating $RUN_ENABLED_FILE"
            rm -f $RUN_DISABLED_FILE
        fi
        : > "$RUN_ENABLED_FILE"
    elif [ "$result" = "$DISABLE" ]; then
        if [ -f "$link_path" ]; then
            if rm -f "$link_path"; then
                debug 1 "disabled. removed existing $link_path"
            else
                ret=$?
                debug 0 "[$ret] disable failed, remove $link_path"
            fi
        else
            debug 1 "already disabled: no change needed [no $link_path]"
        fi
        if [ -e "$RUN_ENABLED_FILE" ]; then
            debug 1 "removing $RUN_ENABLED_FILE and creating $RUN_DISABLED_FILE"
            rm -f "$RUN_ENABLED_FILE"
        fi
        : > "$RUN_DISABLED_FILE"
    else
        debug 0 "unexpected result '$result' 'ds=$ds'"
        ret=3
    fi
    return $ret
}

main "$@"

# vi: ts=4 expandtab