Removing a device

juist remove takes a device out of the network, such as a phone you lost. Every device drops its tunnel as soon as it hears of the removal, and a device cut off from the others drops it at the latest when its freshness expires.

What it is

Removing a device is a change to the network’s log, the signed list of who belongs (see How juist works). Like any change, it needs the approval of your admins, the people whose keys approve changes.

Once the removal is in the log, every device that receives it drops the removed device’s tunnel. The network also gets a new group secret, a key all members share, so the removed device can no longer find the others.

Removing a device

1on an admin's device

Remove the device by its name, its address, or its key (juist devices --keys):

juist remove phone

$ juist remove phone
remove phone (198.18.36.4  fd4c:8a21:e3f:e83:5a7d:f12c:9b46:d371) from "home"? [y/N] y
removed phone

Where a change needs more than one admin, it prints pending … instead and waits for the others to run juist approve (approving changes).

juist log now lists device removal: phone, with the admins who approved it.

What the removed device sees

If it can be reached when the removal is applied, it is told:

phone

$ juist status
home · removed
hint: rejoin with a new invite, or start over: juist reset

To use it again, invite it anew, or run juist reset to leave it in no network, as on a fresh install.

A device that was offline then is not told. It may report itself connected, although no member accepts it any more, or say the network's devices refuse this one: most likely it was removed.

Why it is not instant everywhere

There is no server that tells every device at once. Devices pass changes on to each other, so a device that is offline, or cut off from the others, hears of the removal only when it is back in touch. Until then, it could keep a tunnel to the removed device.

Freshness puts a limit on that. A voucher is a device that confirms every hour that the network’s state is current. The device that created the network is one. A device that no voucher has confirmed for 48 hours keeps tunnels only to vouchers, so it cannot carry a removed device along. Its juist status then shows the state limited and Freshness expired; vouchers only.

This holds only while the vouchers are not cut off together with the device: a voucher keeps every device it still reaches current.

2on an admin's device

Make an always-on device, such as a VPS, a voucher:

juist grant vps voucher

The role is not an admin key. It lets the device confirm the network’s state, and change nothing.

By default, one voucher is enough. A voucher that lies could then keep the devices it reaches on an old view. To guard against that, require several:

juist admins vouchers 2

Now a device trusts its view only when two vouchers have confirmed it within 48 hours. One dishonest voucher is not enough, but two vouchers must be online.

Good to know

juist remove refuses to remove one of the vouchers that juist admins vouchers requires, and says how to lower the number first.
Removing the last voucher warns that freshness then goes unchecked.
If the removed device held an admin key, as a lost laptop might, take that key’s vote away too: juist admins remove. See Admins.
juist remove on the device itself warns that it leaves the network for good.
juist reset on a device the network still lists needs --force. Remove it first where you can.

If something goes wrong

Freshness expired; vouchers only means no voucher has been reachable for 48 hours. Bring a voucher back online; the device is current again once the voucher’s confirmation arrives. See Troubleshooting.