#!/bin/bash
# maravento.com
#
################################################################################
#
# Hardware Clock Sync
# Syncs the hardware clock (hwclock) with the system clock.
# Intended to run at boot via cron (@reboot).
#
################################################################################

set -uo pipefail

# path for cron
export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

# root check
if [ "$(id -u)" != "0" ]; then
    echo "ERROR: This script must be run as root -- abort"
    exit 1
fi

# prevent overlapping runs
SCRIPT_LOCK="/var/lock/$(basename "$0" .sh).lock"
(umask 077; : >> "$SCRIPT_LOCK")
exec 200>"$SCRIPT_LOCK"
if ! flock -n 200; then
    echo "ERROR: script $(basename "$0") is already running -- abort"
    exit 1
fi

# dependencies
for dep in util-linux coreutils; do
    if ! dpkg -s "$dep" &>/dev/null; then
        echo "ERROR: dependency '$dep' is not installed -- abort" >&2
        exit 1
    fi
done

echo "Update HWClock. Wait..."

hwclock -w || echo "WARNING: hwclock -w failed (VM or container?)"
echo "HWClock Update: $(date)" | tee -a /var/log/syslog