The bootstrap node and each of the genesis validators will all create their own copies of the genesis block and confirm they are all the same during the approved block creation protocol (see Initializing the Blockchain -- Protocol for generating the Genesis block). This page describes the inputs needed to produce the genesis block. If all nodes use the same input, they will all get the same genesis block output.
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This is a list of public keys together with the algorithm used to verify signatures (Secp256k1 or ED25519) and a REV balance. Each of these is turned into a "BasicWallet" which exists at the name "@`rho:pubkey:${w.algorithm}:${w.pk}`" and can be accessed using the private key corresponding to the given public key. This input is to be generated from a script which scrapes Ethereum for addresses with RHOC holdings at a given block height. Therefore, the block height is in a sense the real input to the genesis block. Note that in order to avoid duplicate issuance it is required that addresses being used for bonding a genesis validator (see previous section) must not be included in the wallets file. This means some filtering of the output from the script will likely need to occur. Development of this script is being tracked in in RHOL-601.