--- title: "Hibernate When Network Idle"

---
title: "Hibernate When Network Idle"
date: 2020-04-14T20:57:40+10:00
draft: true
tags:
- linux
---

i have a pc at home which is often on, but not so often used. i'd like it to hibernate most of the time, unless i want to use it or it is doing something itself. it's possible, stringing together a few things:

### if the network's idle

Install [vnstat](https://wiki.archlinux.org/index.php/VnStat)

```
pacman -Syu vnstat
```

this allows us to query network usage split up by 5 minute intervals:

```
~ › vnstat -i wlp2s0 -5 4

 wlp2s0  /  5 minute

         time        rx      |     tx      |    total    |   avg. rate
     ------------------------+-------------+-------------+---------------
     2020-04-15
         00:10      2.47 MiB |  835.14 KiB |    3.28 MiB |   91.85 kbit/s
         00:15    913.94 KiB |  398.04 KiB |    1.28 MiB |   35.83 kbit/s
         00:20    410.53 KiB |  301.39 KiB |  711.92 KiB |   19.44 kbit/s
         00:25    657.27 KiB |  750.08 KiB |    1.37 MiB |   38.43 kbit/s
     ------------------------+-------------+-------------+---------------
```

using this we'll query the usage over the last 5 minutes using `jq`

```
~ › vnstat -i wlp2s0 -5 1 --json 1 | jq ".interfaces[0].traffic.fiveminute[0]"
```

```json
{
  "id": 169,
  "date": {
    "year": 2020,
    "month": 4,
    "day": 15
  },
  "time": {
    "hour": 0,
    "minute": 25
  },
  "rx": 673042,
  "tx": 768082
}
```

### sleep for a while

by default this simply suspends, which is quick to start again, but isn't the lowest power consumption mode.

```sh
rtcwake --date "+30min"
```

it gave me `rtcwake: write error` unless i explicitly specified `-m mem`

```sh
sudo rtcwake -m mem --date "+5min"
```

```sh
or rtcwake -m no -l -t $(date +%s -d 'tomorrow 10:00')?
```

https://jlk.fjfi.cvut.cz/arch/manpages/man/rtcwake.8.en

### cron job

we want to control when the napping will occur, and sleep for different times throughout the day. something like

* 3am ~ 6am: sleep time
* 6am ~ 10am: wake during morning
* 10am ~ 4pm: afternoon nap
* 4pm ~ 3am: wake during evening

```
~~~~
```

### roll it into a script we can run periodically

```sh
#!/bin/zsh

# Usage: ./nap-if-idle.sh "+30min"

# arg 1
# duration of nap
NAP_TIME="+30min"

# arg 2
# how deep is the sleep
SLEEP_MODE="mem"

RX=$(vnstat -i wlp2s0 -5 1 --json 1 | jq ".interfaces[0].traffic.fiveminute[0].rx")
TX=$(vnstat -i wlp2s0 -5 1 --json 1 | jq ".interfaces[0].traffic.fiveminute[0].tx")
TOTAL_KB=(( $RX + $TX_))
IDLE_KB=(( 1 * 1024 )) # 1 MiB

if [[ $TOTAL -gt $IDLE_KB ]]; then
  echo 'System seems to be idle, having a nap' | systemd-cat
  rtcwake --date $NAP_TIME
fi

```