Making a Linux Home Server Sleep on Idle and Wake on Demand (2023)
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Home ServerPower ManagementWake-on-Lan
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Home Server
Power Management
Wake-on-Lan
The post describes a Linux home server setup that sleeps on idle and wakes on demand using a Raspberry Pi, sparking discussion on the complexity and energy efficiency of such a setup.
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Works good IME, but you have to plug it into the wall first. Sometimes if you plug the appliance in, and then plug the KAW in, it will miscalibrate
https://www.brennenstuhl.co.uk/en-GB/products/travel-adapter...
It’s very easy for even the small things to add up.
(5800X + 64GB)
I can enable Eco Mode in the BIOS, which will bring down the CPU to about 65W max although its still at about 100W total system.
(looking at my 330W laptop charger)
I’m not sure that is the constraint you think it is.
I'd love it if I could turn off my systems for when I really need them.
It's surprising because reddit (and HN) would make you think you're throwing away tons of money unless you go with some tiny ARM board and that's not true.
The main issue for me is the heat. I've got it next to me and 130W of heat adds up in the summer.
Making a Linux home server sleep on idle and wake on demand – the simple way - https://news.ycombinator.com/item?id=35627107 - April 2023 (237 comments)
In in the end I just went the whole hog and set up a PiKVM, so now if I mess up the machine's networking (or even completely break the OS) I can still recover it remotely even though it doesn't have a proper BMC or anything like that.
In general this approach seems ugly in principle but I really like it in practice. It lets you retrofit solid remote capabilities onto consumer hardware. That way you have such a broader market to buy from.
It's pretty funny that you have both the input and output physically installed in and powered by the chassis, but then you run cables to connect them!
It would seem reasonable to at least have the option to have it directly enumerate as a USB hub/display device on the PCIe bus it gets power from! But maybe that would add a lot of bulk/cost?
I take it you're in the US? Because it seems I (in Europe) could order it from Aliexpress, see the link on https://github.com/sipeed/NanoKVM.
EDIT: It seems the NanoKVM is struggling with one of the most fundamental KVM tasks, though: https://github.com/sipeed/NanoKVM/issues/594
I really liked the PCIe form factor, but it looks like I'll have to go for https://tinypilotkvm.com/ instead.
Of course, the RockPi doesn't give you any KVM like functionality, though.
[1]: https://wiki.radxa.com/RockpiS
I know a lot of sysadmins / platform engineer types. A lot of them really enjoy the mix of hardware and software integration challenges.
I guess everyone has to go through it.
Bingo, but some people never stop tinkering - their joy is in avoiding the well trod path.
Fortunately, the author wrote a derailed essay explaining all of this…
> You should never add more failure points to infra, ever.
Every time you add a new system or a new feature you necessarily “add more failure points”, there's no way around that.
One should avoid introducing more failure points than needed for the functionality you want, that's it.
You say it's a “solved problem”, but you only give solutions to a different problem (starting the server at a scheduled time, when the author wants to start the server on demand).
Anyway it's not about the money for me it's any the aesthetics. Burning power for nothing is yucky.
Edit: just been Googling around. OP is running one of these HP mini PCs. They are pretty efficient! Some go well below 10W. So yeah I would say for the specific use case it's unlikely to matter very much. But still it's a useful thing to be able to do in general.
(I also heard that it sometimes suggests power saving modes that are usually switched off for a good reason, like apparently you really don't want some USB controllers going into certain sleep modes as they take seconds to come back).
Looking at powertop, the various qemu virtual machines have high events/sec compared to host processes. There are also a couple of timers - tick_nohz_handler and hrtimer_wakeup - which seem to generate hundreds of events per second.
If you are willing to send magic packets to wake up the server, before using it, you can save money from the electricity bill with negligible complexity.
(For example, imagine a big home GPU server that is needed only intermittently, and you want it to spin up automatically on network traffic from family's various devices that you can't modify.)
Of course, if you have simpler needs, and you're willing to send a WOL magic packet from the using devices, you can do in a few lines of shell script. It's a 1-line ssh-to-something-that-can-etherwake-on-that-vlan script, then wait in a loop for the service you need to appear, then 1-line ssh-to-server-to-shutdown when you're done.
Crunched the numbers for mine - about 150 bucks a year in potential savings.
I always choose “make more money” over “pinch pennies”.
no need for a standin
This is particularly common if the NIC is a power hungry 10GbE port.
However, in the particular case I found, the motherboard also disables oower to any usb GigE adapter attached.
The solution I found was to attach a USB hub with (empty) SD slots and integrated GigE port. As SD cards require power to remain mounted, the motherboard did not shutdown power to this adapter and WoL worked.
If you use Windows, check in device manager for a setting to allow the device to wake up the computer. (I can't remember the exact name.)
My Desktop, WoL on, tested to be working Android Phone, always on
All have SyncThing installed. Mobile had Tasker installed.
So, the idea was to have Tasker monitor a folder inside SyncThing, When I need my computer, I put a file inside that folder, when Tasker finds that folder, it sends WoL to my desktop, and deletes the file, Computer wakes up. When I see the file deleted I know, the beast is now awakens ....
When I actually did try that from Thailand, the file did not got deleted, nor the beast woke up.
What happened? Turns out, my mobile restarts automatically after some time of inactivity. Which, locks Tasker out, and the whole process fails.
So, operation wake the beast was busted.
Now I just need to get enough momentum to set up the process of waking up my desktop as needed and set up radical caldav server in the mobile.
Or login into the router and send WoL from there?
Or have Raspberry always on with ssh?
Or set a power-on timer in BIOS/UEFI once a day and a shutdown/sleep in cron? (This is also a good failsafe if WoL doesn't work.)
Hm, so never tried something like that before actually, I think for OpenWrt I need to install arp packages. I do not have public IP any more though, was getting hammered by bot network and found Tailscale to do what I need.
> Or login into the router and send WoL from there?
Restricted outside access to the router management panel, only port forwarded to the desktop.
> Or have Raspberry always on with ssh? I do not have one, which is why used a mobile, thought to be next best thing. As, power outages happen regularly, I need something that would be able to keep on running.
> Or set a power-on timer in BIOS/UEFI once a day and a shutdown/sleep in cron? (This is also a good failsafe if WoL doesn't work.)
That's easily workable for my setup, actually!
Thank you for giving me the ideas!
> Hm, so never tried something like that before actually, I think for OpenWrt I need to install arp packages.
No, you don't. Put this in /etc/firewall.user or /etc/rc.local (you can do it from UI) and forward a UDP port to 192.168.0.254 or whaterver subnet you're using:
The incoming packet will be broadcasted (ff:ff...) on the br-lan interface. 192.168.0.254 doesn't need to exist - the sleeping computer doesn't care.Correction! /etc/rc.local isn't OK. The ARP record needs to be reloaded if br-lan interface is restarted, such as when changing other network settings in WebUI. So only /etc/firewall.user will do.
The version in the OpenWrt didn't support the full command. Had to update to `ip-full`.
After the command was successful, I can see the entry in the `ip neigh` table.
Now digging around
For failsafe, KVM might be the ultimate solution in case boot got stuck.
I for one just leave the beast on, I understand that spin-ups and downs are the main thing that wreck harddrives (and my beast has a lot.)
For me, power outages were/are a big issue, lost one of the HDD recently then, did not want to risk the new one.
https://www.amazon.de/Mechanical-Analogue-Switching-Christma...
It's a more rigid solution that doesn't let you ssh in (unless during backup time ;-), but it saves electricity and it is implemented in 10 minutes (5 for an Amazon order and 5 to plug in and set the timer to your backup hours). It's also a more robust solution - little can go wrong (the only thing is you need to balance backup time against electricity/time savings as backup size grows).
So instead of the Pi solution, how about using a server that idles at 10-20 W?
There's a bit of a writeup here: https://www.sicsa.ac.uk/wp-content/uploads/2024/11/LOCO2024_...
You could set a calendar schedule for waking up itself and backing up the clients, and at night the server would go into standby only if no clients were running anymore since X minutes.
Does a Pixel 5 have wake on Lan? Do any cellphones?
But this is about waking up on non-magic requests, just any request?