server-monitor.sh

#!/bin/sh

IP="192.168.2.2"                    # server IP
MAC="50:EB:F6:50:3E:AE"             # MAC address for WOL
INTERFACE="br-lan"                  # network interface for ping/etherwake
INTERFACE_RESTART="lan1"       # interface to restart
MAX_FAILS=4                         # 4 * 5 min = 20 min
STATE="/tmp/server-monitor.state"   # temp file for fail counter
LOG_TAG="server-monitor"            # logger tag

# function to log messages
log() {
    logger -t "$LOG_TAG" -- "$1"
}

# function to check host availability
check_host() {
    log "Checking host $IP via interface $INTERFACE (fail count: $FAILS)"
    if ping -c1 -W1 -I "$INTERFACE" "$IP" >/dev/null 2>&1; then
        echo 0 > "$STATE"
        log "Host $IP is up"
        exit 0
    else
        log "Host $IP is not responding (fail count: $FAILS)"
    fi
}

# read current fail count or 0
[ -f "$STATE" ] && FAILS=$(cat "$STATE") || FAILS=0

# check if interface exists
if ! ip link show "$INTERFACE" >/dev/null 2>&1; then
    log "Interface $INTERFACE not found, cannot ping host"
    exit 1
fi

# ping host
check_host

# restart interface
if ip link show "$INTERFACE_RESTART" >/dev/null 2>&1; then
    log "Restarting interface $INTERFACE_RESTART"
    ip link set "$INTERFACE_RESTART" down
    sleep 1
    ip link set "$INTERFACE_RESTART" up
    sleep 2
    log "Interface $INTERFACE_RESTART was restarted"
    
    # check host again after interface restart
    check_host
else
    log "Interface $INTERFACE_RESTART not found, skipping restart"
fi

FAILS=$((FAILS+1))
echo $FAILS > "$STATE"

# send WOL if needed
if [ "$FAILS" -ge "$MAX_FAILS" ]; then
    log "Host $IP has been down for too long, sending WOL packet"
    etherwake -i "$INTERFACE" "$MAC"
fi