Feature Request: Sign voluntary exit without broadcast

[alex-miller-0]

Now that withdrawals are enabled, I would like to generate pre-signed voluntary exit messages as insurance against a nuclear meltdown on my staking box, i.e. something that would cause a long offline period (e.g. natural disaster, hardware failure, etc). This could generate a JSON file with the signed data, which could be backed up on another device and later broadcast to any available beacon node (e.g. there are public nodes which could be used to broadcast without an active staking box). Obviously this would be for emergencies only, as I would be signing up for ~4 days of penalties prior to exiting, but it would bound the risk of running a staker.

Currently, voluntary exits on Lighthouse assume you are exiting immediately - it would be much appreciated if you could add a flag to decouple this from the actual signing process (e.g. --prepare-offline).

[michaelsproul]

This will be available in v4.1.0 via the VC HTTP API, docs: https://ethereum.github.io/keymanager-APIs/?urls.primaryName=dev#/Voluntary%20Exit/signVoluntaryExit.

We're also working on CLI tooling for interacting with the VC API, in this PR: #3502.

[alex-miller-0]

Haha amazing timing on that release. Just tested and it works great - thanks!

Closed by #4119

[mrabino1]

is there any documentation on how to use (via CLI) what you are planning on the lighthouse book? or other source? eg.. what is the command? thx