How to record net traffic before net closed when to poweroff? - iptables

Question

I want to record net traffic everytime on debian8.
Here is my way.
sudo vim /etc/systemd/system/graphical.target.wants/Ktraffic.service
[Unit]
Description=Record net traffic
[Service]
Type=oneshot
ExecStart=/bin/bash /etc/init.d/K01trafficLog.sh
[Install]
WantedBy=poweroff.target
sudo vim /etc/init.d/K011trafficLog.sh
#!/bin/bash
trafficlog="/var/log/traffic.log"
echo `date "+%Y-%m-%d %H:%M:%S "` >> $trafficlog
iptables -v -L INPUT |grep Chain >> $trafficlog
systemctl enable ktraffic.service
To check the traffic log file when to reboot.
sudo cat /var/log/traffic.log
2017-02-05 10:49:31Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
2017-02-05 11:40:25Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
no packets number recorded in /var/log/traffic.log.
Network connection was closed before execution of /etc/init.d/K011trafficLog.sh,how to make it execute before network connection colsed?
Which service closed network connection during poweroff?
systemctl |grep net - vim
(standard input):sys-devices-pci0000:00-0000:00:1c.2-0000:03:00.0-net-eth0.device loaded active plugged RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
(standard input):sys-subsystem-net-devices-eth0.device loaded active plugged RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
(standard input):netfilter-persistent.service loaded active exited netfilter persistent configuration
(standard input):network-online.target loaded active active Network is Online
(standard input):network.target loaded active active Network
vim:sys-devices-pci0000:00-0000:00:1c.2-0000:03:00.0-net-eth0.device loaded active plugged RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
vim:sys-subsystem-net-devices-eth0.device loaded active plugged RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
vim:netfilter-persistent.service loaded active exited netfilter persistent configuration
vim:network-online.target loaded active active Network is Online
vim:network.target loaded active active Network
Is the network.service to close my network when poweroff?
sudo vim /etc/systemd/system/graphical.target.wants/Ktraffic.service
[Unit]
Description=Record net traffic
Before=networking.service
[Service]
Type=oneshot
ExecStart=/bin/bash /etc/init.d/K01trafficLog.sh
[Install]
WantedBy=poweroff.target
To reboot to test it, my issue remains.
I set a flag in /var/log/syslog.
echo "it is a flag here to get output info of poweroff " | sudo tee -a /var/log/syslog
To reboot and get syslog as following.
[![enter image description here][1]][1]
Which service result in info Starting Synchronise Hardware Clock to System Clock?

Answer 1

Thank to Ferenc Wágner .
solution to Execute simple script before shutdown and reboot
It is right fromat to record network traffic on my eth0.
[Unit]
Description=Record net traffic
Before=shutdown.target reboot.target halt.target poweroff.target
[Service]
Type=oneshot
RemainAfterExit=true
ExecStart=/bin/bash
ExecStop=/bin/bash /etc/init.d/K01trafficLog.sh
[Install]
WantedBy=poweroff.target shutdown.target reboot.target halt.target