Booting Zero-OS, should we leave the USB key in?

Hi farmers,

I think there is often this question coming up in the DIY community:

Do I need to leave the USB key on my 3node once it has properly booted?

The answer is: yes. It is advised. Why? Because…

The node needs the USB key plugged in to boot Zero-OS properly. The 3node uses the USB key to connect to the Internet and download what is needed to boot 100% correctly Zero-OS.

Once your node has been booted with Zero-OS via the USB key, you can remove the USB key, but if something happens and the node needs to reconnect with the network, it won’t be able to do so. We advise people to let the USB key always in so the node can reconnect with the network if needed. As Scott explains:

Some DIYers will thus choose a small USB key such as this one:


This has the advantage of taking fewer space. Note that you don’t need a lot of storage on the USB key, so this could help cut costs. The v.3 Zero-OS .img is 2.1 MB as of 01-2022.

Also, some DIYers will use a USB key that has a “light” on when it is properly booted, this can help you know with a quick look that the node is still online and running. Next picture shows some model of a USB key that has a light included. The light flashes when it is being used (in this case, when the 3node is actively connecting online to the network), it stays open when Zero-OS is running normally, and it will shut down its light when the computer is off.


I won’t post the links to buy the USB keys. DYOR.

Also, note that the Zero-OS Boostrap Image you used to boot your first 3node can be duplicated/flashed on another USB key for an additional 3node. You do not need to redownload the image. You can simply flash another USB key (on Balena Etcher, or else). The reason is simple: your 3node simply needs to know your Farm ID to link properly, and the Farm ID is on the Zero-OS Bootstrap Image you downloaded on the website: (currently for Grid v3) and (for Grid v2)
(Make sure to choose production mode)

For an amazing 3node DIY guide:

If you have questions or want to comment on this, feel free to do so!

If I have not been clear in my explanations, please tell me where I went wrong, and I will update the post.

Have a good day, you Farmer of the New Internet!


Thanks so much for posting that valuable information dear @Mik!!!
Really appreciated :pray: and super grateful you are such an active and collaborative Farmer of the New Internet :wink: AHO my friend! continue to shine this light into the world :bulb: Thank you for being you.


Nice work, and thank you for this :slight_smile:

I’ll add a note based on a recent question from Telegram. As you mention, booting from the network helps to ensure correct booting of Zos. Some farmers rightly wonder though, wouldn’t it be more efficient to store Zos on disk like any other operating system? Booting over the network helps the security of the Grid too. An operating system stored on disk can be modified relatively simply, whereas an operating system that’s only stored in RAM is very difficult to tamper with.


That is exactly the kind of additional information the post was missing. I edited the post and added your explanation so the core information is in one post. Thanks!


By security key are you referring to the USB that we flashed the Bootstrap image to? or something else? If I allow the Zos USB in my system and it restarts won’t that try to install another Zos on top of the current one thus replacing the node with a new node?
If a security key is something different, then how can I create one?
Please forgive my ignorance I am new to this and trying to learn.


Don’t worry, we all ask questions at first. That’s how we learn. Let me see if I can make it clearer:

I haven’t mentioned security key. Your security key, if I understand you correctly, is the seed phrase you have and must not reveal. This security key is linked to your polkadot.js account ( With this account, you create a farm, which comes with a farm id. With the farm id, you can create a bootstrap image on a USB key. There you can add an address where you will receive your TFT rewards.

When you connect your 3node (farming computer) with the USB key (which contains your farm id) on the Threefold grid, it will link to the network and create a new node id. This node id will be stored in your first SSD disk that you connect.

The node id is stored and stay there. When you restarts, it will not change the node id, nor the farm id. It will simply reconnect with zero-os network.

Hope it helps!

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I am sorry I meant the USB Key. I must have been thinking about something else when I wrote that.
So by USB key are you referring to the USB that has the bootstrp image on it? or something else?
I created a DIY node on Grid 3 and it was up. But when I moved it to a different spot and restarted it, it didn’t start back to Zos. I was wondering if I should left the installation USB there? But if I do that won’t it boot off of the USB and reinstall Zos?

Exactly, the USB key is the USB image bootstrap. and YES you need to let the USB key in when you power on the unit.

Every time you power on your 3node, it needs the USB key in. The USB key has your zero-os image bootstrap. It will then connect to the Internet and download what is needed to properly boot zero-os entirely.

It is tricky at first. But it is quite simple: the bootstrap image is not copied on your 3node. The 3node needs the USB key/bootstrap image to connect online and download the rest of zero-os.

We recommend to let the USB key/bootstrap image in, in case the network needs to reboot the 3node if something happens.

I hope it helps!


In addition to the great info given by @Mik, perhaps it’s helpful to say it this way: Zero OS never gets installed to your node. It is downloaded and runs in memory, then gets forgotten when the node powers down. See my original reply here on why that’s the case, and feel free to keep the questions coming if anything sill isn’t clear :slight_smile:


Thank you very much guys. This solves my problem. For some reason I thought of this USB key as windows installation USB which will continue installing windows if you don’t remove it after the reboot. That is why I would remove the USB after installing Zero OS.
This clarifies everything for me. I kept my USB key this time and that did the trick. Now the system is up and running. I need to create a USB key for my other system as well.
Again, Thank you both.

Very well explained, @Mik and @scott! :bulb:

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