EVM-compatible chain secured by the Lachesis consensus algorithm.

Building the source

Building opera requires both a Go (version 1.14 or later) and a C compiler. You can install them using your favourite package manager. Once the dependencies are installed, run

make opera

The build output is build/opera executable.

Running opera

Going through all the possible command line flags is out of scope here, but we’ve enumerated a few common parameter combos to get you up to speed quickly on how you can run your own opera instance.

Launching a network

Before first launching of your mainnet node you will need appropriate genesis file:

wget https://opera.fantom.network/mainnet.g

Or for testnet node:

wget https://opera.fantom.network/testnet.g

Launching opera readonly (non-validator) node for network specified by the genesis file:

$ opera --genesis mainnet.g


As an alternative to passing the numerous flags to the opera binary, you can also pass a configuration file via:

$ opera --config /path/to/your_config.toml

To get an idea how the file should look like you can use the dumpconfig subcommand to export your existing configuration:

$ opera --your-favourite-flags dumpconfig


New validator private key may be created with opera validator new command.

To launch a validator, you have to use --validator.id and --validator.pubkey flags to enable events emitter.

$ opera --nousb --validator.id YOUR_ID --validator.pubkey 0xYOUR_PUBKEY

opera will prompt you for a password to decrypt your validator private key. Optionally, you can specify password with a file using --validator.password flag.

Participation in discovery

Optionally you can specify your public IP to straighten connectivity of the network. Ensure your TCP/UDP p2p port (8050 by default) isn’t blocked by your firewall.

$ opera --nat extip:


Running testnet

The network is specified only by its genesis file, so running a testnet node is equivalent to using a testnet genesis file instead of a mainnet genesis file:

$ opera --genesis /path/to/testnet.g # launch node

It may be convenient to use a separate datadir for your testnet node to avoid collisions with other networks:

$ opera --genesis /path/to/testnet.g --datadir /path/to/datadir # launch node
$ opera --datadir /path/to/datadir account new # create new account
$ opera --datadir /path/to/datadir attach # attach to IPC


Lachesis has extensive unit-testing. Use the Go tool to run tests:

go test ./...

If everything goes well, it should output something along these lines:

ok  	github.com/Fantom-foundation/go-opera/app	0.033s
?   	github.com/Fantom-foundation/go-opera/cmd/cmdtest	[no test files]
ok  	github.com/Fantom-foundation/go-opera/cmd/opera	13.890s
?   	github.com/Fantom-foundation/go-opera/cmd/opera/metrics	[no test files]
?   	github.com/Fantom-foundation/go-opera/cmd/opera/tracing	[no test files]
?   	github.com/Fantom-foundation/go-opera/crypto	[no test files]
?   	github.com/Fantom-foundation/go-opera/debug	[no test files]
?   	github.com/Fantom-foundation/go-opera/ethapi	[no test files]
?   	github.com/Fantom-foundation/go-opera/eventcheck	[no test files]
?   	github.com/Fantom-foundation/go-opera/eventcheck/basiccheck	[no test files]
?   	github.com/Fantom-foundation/go-opera/eventcheck/gaspowercheck	[no test files]
?   	github.com/Fantom-foundation/go-opera/eventcheck/heavycheck	[no test files]
?   	github.com/Fantom-foundation/go-opera/eventcheck/parentscheck	[no test files]
ok  	github.com/Fantom-foundation/go-opera/evmcore	6.322s
?   	github.com/Fantom-foundation/go-opera/gossip	[no test files]
?   	github.com/Fantom-foundation/go-opera/gossip/emitter	[no test files]
ok  	github.com/Fantom-foundation/go-opera/gossip/filters	1.250s
?   	github.com/Fantom-foundation/go-opera/gossip/gasprice	[no test files]
?   	github.com/Fantom-foundation/go-opera/gossip/occuredtxs	[no test files]
?   	github.com/Fantom-foundation/go-opera/gossip/piecefunc	[no test files]
ok  	github.com/Fantom-foundation/go-opera/integration	21.640s

Also it is tested with fuzzing.

Operating a private network (fakenet)

Fakenet is a private network optimized for your private testing. It’ll generate a genesis containing N validators with equal stakes. To launch a validator in this network, all you need to do is specify a validator ID you’re willing to launch.

Pay attention that validator’s private keys are deterministically generated in this network, so you must use it only for private testing.

Maintaining your own private network is more involved as a lot of configurations taken for granted in the official networks need to be manually set up.

To run the fakenet with just one validator (which will work practically as a PoA blockchain), use:

$ opera --fakenet 1/1

To run the fakenet with 5 validators, run the command for each validator:

$ opera --fakenet 1/5 # first node, use 2/5 for second node

If you have to launch a non-validator node in fakenet, use 0 as ID:

$ opera --fakenet 0/5

After that, you have to connect your nodes. Either connect them statically or specify a bootnode:

$ opera --fakenet 1/5 --bootnodes "enode://[email protected]:5050"

Running the demo

For the testing purposes, the full demo may be launched using:

cd demo/
./start.sh # start the Opera processes
./stop.sh # stop the demo
./clean.sh # erase the chain data

Check README.md in the demo directory for more information.


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