Read Part I and Part II.

Summary: A hard fork will transfer all ETH to a refund address. As soon as you interact with the Ethereum chain you should update your client.

What will the hard fork do?

The hard fork will transfer all Ether from all DAO contracts, their children, and their extra balances to a refund contract. Every token holder of the main DAO can use this contract to exchange DAO tokens for ETH 100:1. All of the Ether that is left over after this will be sent to a multisig contract controlled by the curators. This Ether will be used to refund the split DAOs and, as much as possible, those people who purchased DAO tokens at a rate other than 100:1 during the creation period. You can read the technical specification here.

Is my Ether at risk if I do nothing?

No. If you only hold Ether in a cold wallet, for example, there is no immediate need to act. However, as soon as you do any kind of transaction or rely on data from the blockchain, you need to make sure to update to the latest software and make sure that you are on the right chain.

How exactly will the refund work?

You will need to do two transactions for each account that holds DAO tokens. A first transaction will allow the refund contract to transfer your DAO tokens. This transaction will need to be sent to the DAO contract. A second transaction will trigger the actual refund. In this transaction, the refund contract will first transfer your DAO tokens to itself and then pay out Ether 100:1 in exchange. Most likely UIs will be created to do those two steps very easily. It is also possible that exchanges will offer this as a service.

Is there a time limit to exchange DAO-tokens into ETH?

No. This option will exist until all tokens are exchanged.

Will DAO tokens be treated differently depending on at what price they were initially bought in the creation period?

No, since DAO tokens are fungible and have been moved, mixed and traded there is no good way to do this. Therefore all Tokens will have a value of ETH/100 and an additional refund for those who bought into the DAO in last two weeks of the creation period will go directly to the addresses used back then even if the DAO tokens have been moved or sold already.

What should I consider if I bought in Ether late?

Do not lose your private key for the account that you used to buy in. Even if you have spent all Ether from this account and all DAO tokens are transferred, this key will still be valuable for getting the additional refund.

Why did the fork also effect “regular splits”?

First, to simplify the HF code, but, even more importantly, to also protect those DAOs who did a regular split. Otherwise, there might have been attacks on those split DAOs. The disadvantage for those who split out is that they will have to wait slightly longer for a refund. How to handle some edge cases (such as those who split after the attack) still needs to be discussed.

When will a fork occur?

The fork is planned for block 1,920,000, this block will be mined on July 20.

What do I as a user have to do?

Every user will face the option to switch on the hard fork or not. If you do nothing (and do not update your software) you will chose against the hard fork. In the case that the majority of the Ethereum ecosystem decide for the hard fork this will cause problems and eventually the loss of Ether (if you do transactions).

Will the fork effect other parts of the Ethereum ecosystem?

No. All contracts, accounts, and transactions that are not directly part of the hard fork are affected in no way.

Will it be possible to revert any kind of hack with a hard fork in this way if the community agrees?

No, not at all. The reason this hard fork can be done without any transaction rollback is purely based on the fact that there have been some delay times built into the contract that effectively locked all Ether for a period of time. Only because of this fact is it possible to do such a fork with little interference. If the attacker would have had full control over the Ether immediately, it would be very easy to, in a way, mix the coins into existing contracts so that it becomes impossible to revert a hack without rolling back the blockchain. Such a fork is unlikely to ever find a majority.

How was the decision for a hard fork made?

Well, it is not decided yet. In the end it will be the voice of every user individually deciding to do or not to do it. However, because of network effects it is highly likely that a majority will rapidly evolve into a super majority. Based on the opinions expressed on social networks, calls and chats of core developers, groups that represent miners, opinions of important exchanges and companies, it is highly likely that all of those groups will overwhelmingly support a hard fork.

Which exchanges are supporting the hard fork?

Most exchanges have published some letter on how they will handle the hard fork. Most said they will stick to the chain with the most miner support. Some exchanges (e.g. Poloniex) have offered to once give the option to withdraw ETH on the loosing chain. An official statement from Kraken:

ETH deposits and withdrawals will be disabled approximately 1 hour before the hard fork activates. Trading will continue as normal during the fork. All ETH on Kraken after the fork will be tokens of the winning chain (i.e. the chain with the most work on it). ETH deposits and withdrawals will be enabled again once the winning chain has become clearly evident. We expect the hard fork process to be smooth and quick, but there is no certainty of this.

Will exchanges halt trading at any time?

All exchanges have signaled to continuously allow trading but halt with deposits and withdrawals around the HF.

The HF is scheduled on July 20, 33 days after the hacker stole the 3.6M Ether. Will it be early enough to prevent the hacker from removing the Ether from the childDAO?

The hard fork is scheduled on purpose on a date that does not allow the attacker to spilt the ETH into a third DAO. The creation period of the DAO is 27 Days + 7 days for a split proposal.

Which exchanges will remain on the current chain?

No exchanges have explicitly said they will allow trading old ETH even against a broad community decision for the fork.

Things to consider if both chains continue to exists and have economic value:

There is the possibility that after the fork both versions of Ethereum will continue to exist (i.e., new blocks are mined), especially if Ether on both chains has some economic value. Thus, you should consider a few things. First of all, you will have your Ether on both chains, at least if you are in direct control of the ETH (you hold the keys). If you have the ETH only on an exchange, it depends on the behaviour of the exchange. If you think it is likely that both chains have value and your exchange has not signaled that they will support withdrawals on both chains, you should potentially withdraw before the fork.

The replay attack:

If two chains exist one problem is that a transaction made on one chain might be a valid transaction on the other chain, as well. There are a few options to make sure the transaction is only valid on one chain. The best tip for none technical users: if there are two chains with economic value DON’T do any transactions unless you are fine with the transaction being executed on both chains. Let’s say you exchange ETH on Shapeshift for BTC and Shapheshift accepts the main chain, only there is no need to give them the option to collect your ETH on the other chain, as well. So in this case you better wait until tools are available to solve this problem.