This page explains the configuration of SCNs to form a consensus network.

If you installed archive distribution, you can find the binaries and the config file in the directories you extracted the archives. Below is an example of command execution.

$ homi-darwin-amd64/bin/homi setup ...
$ kscn-darwin-amd64/bin/kscnd start
$ vi kscn-darwin-amd64/conf/kscnd.conf

In this tutorial, we will not always specify the full path to the command.

Creation of a Genesis File

First, you should create a genesis file and a nodekey file for your own service chain. You can create them using homi like below.

$ homi setup local --cn-num 1 --servicechain -o ./homi-output
Created : homi-output/keys/passwd1
Created : homi-output/scripts/genesis.json
Created : homi-output/keys/nodekey1
Created : homi-output/keys/validator1
Created : homi-output/scripts/static-nodes.json
Created : homi-output/Klaytn.json
Created : homi-output/Klaytn_txpool.json

Below are examples of genesis file and nodekey file.

$ cat homi-output/scripts/genesis.json
"config": {
"chainId": 1000,
"istanbul": {
"epoch": 3600,
"policy": 0,
"sub": 22
"unitPrice": 0,
"deriveShaImpl": 2,
"governance": null
"timestamp": "0x5dca0732",
"extraData": "0x0000000000000000000000000000000000000000000000000000000000000000f85ad594f8690562c0839c44b17af421f7aaaa9f12dcc62bb8410000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000c0",
"governanceData": null,
"blockScore": "0x1",
"alloc": {
"f8690562c0839c44b17af421f7aaaa9f12dcc62b": {
"balance": "0x2540be400"
"number": "0x0",
"gasUsed": "0x0",
"parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000"
$ cat homi-output/keys/nodekey1

Please change the chainID in the genesis file. Use your own number to prevent a replay attack. (Do not use the same chainID with Klaytn Cypress (8217) and Baobab (1001))

If you want, you can change the pre-funded addresses by editing "alloc" in the genesis file. (You can find more details in Genesis JSON.)

SCN Data Directory Creation

Considering the fact that the size of Klaytn blockchain data keeps increasing, it is recommended to use a big enough storage. You can create the data directory on your desired path. In this document, we create ~/kscnd_home as a data directory.

$ mkdir -p ~/kscnd_home

Initialization of a Genesis Block

After that, you can initialize the data directory with the genesis file. Before starting a service chain node, it is necessary to initialize the genesis block of the service chain network using kscn and genesis.json.

$ kscn init --datadir ~/kscnd_home homi-output/scripts/genesis.json
WARN[11/12,10:13:58 +09] [19] Some input value of genesis.json have been set to default or changed
INFO[11/12,10:13:58 +09] [18] Setting connection type nodetype=cn conntype=0
INFO[11/12,10:13:59 +09] [5] Using DeriveShaConcat!
INFO[11/12,10:13:59 +09] [5] Writing custom genesis block
INFO[11/12,10:13:59 +09] [5] Using DeriveShaConcat!
INFO[11/12,10:13:59 +09] [47] Persisted trie from memory database updated nodes=1 updated nodes size=80.00B time=304.931µs gcnodes=0 gcsize=0.00B gctime=0s livenodes=1 livesize=0.00B
INFO[11/12,10:13:59 +09] [19] Successfully wrote genesis state database=lightchaindata hash=0xc269669079fc8c06ac37435a563b8ed8ef273c1c835f3d823d2e586315319aa8
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/header
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/body
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/receipts
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/statetrie/0
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/statetrie/1
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/statetrie/2
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/statetrie/3
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/txlookup
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/misc
INFO[11/12,10:13:59 +09] [46] Database closed path=/Users/ethan/kscnd_home/klay/lightchaindata/bridgeservice

Install nodekey

Copy homi-output/keys/nodekey1 to the klay directory in the SCN's data directory like below.

$ cp homi-output/keys/nodekey1 ~/kscnd_home/klay/nodekey

Configuration of the SCN

kscnd.conf is the configuration file for the SCN.

Assume that the SCN uses the default port and mounts a large-scale partition onto ~/kscnd_home. In the default kscnd.conf file, SC_SUB_BRIDGE option is disabled and DATA_DIR is empty.

# Configuration file for the kscnd

You can enable SC_SUB_BRIDGE to use the Anchoring/Value transfer feature. Also you should set the DATA_DIR like below.

# Configuration file for the kscnd

If you want, you can further modify other options to customize your Service Chain. Otherwise, now you can finish the configuration and you are ready to run the service chain using the default configuration.