Configuring Juno ⚙

Juno can be configured using several methods, with the following order of precedence:

1. Command line parameters (flags)
2. Environment variables
3. Configuration file

Command line params

Juno can be configured directly on the command line by prefixing -- to each option name:

./build/juno --http --http-port 6060 --http-host 0.0.0.0

When using Docker, append the command line parameters after the image name to configure Juno:

docker run nethermind/juno --http --http-port 6060 --http-host 0.0.0.0

tip

Command line parameters override environment variables and configuration file.

Environment variables

Juno can be configured through environment variables by prefixing the variable names with JUNO_ and using the configuration options in SCREAMING_SNAKE_CASE format.

To set the http, http-port, and http-host configurations, Juno should be run in this format:

JUNO_HTTP=true JUNO_HTTP_PORT=6060 JUNO_HTTP_HOST=0.0.0.0 ./build/juno

When using Docker, start Juno using the -e command option:

docker run \
  -e "JUNO_HTTP=true JUNO_HTTP_PORT=6060 JUNO_HTTP_HOST=0.0.0.0" \
  nethermind/juno

tip

Environment variables rank second in configuration precedence. Command line parameters override environment variables.

Configuration file

Juno can be configured using a YAML file:

Sample YAML File

log-level: info
network: mainnet
http: true
http-port: 6060
metrics: true
metrics-port: 9090

To run Juno with a configuration file, use the config option to specify the path of the configuration file:

# Standalone binary
./build/juno --config <CONFIG FILE PATH>

# Docker container
docker run nethermind/juno --config <CONFIG FILE PATH>

info

By default, Juno looks for the configuration file in the $XDG_CONFIG_HOME directory.

tip

Configuration file rank third in configuration precedence. Command line parameters and environment variables override configuration file.

Configuration options

To list all available command line options, you can use the --help parameter:

# Standalone binary
./build/juno --help

# Docker container
docker run nethermind/juno --help

Below is a list of all configuration options available in Juno, along with their default values and descriptions:

Config Option	Default Value	Description
cn-core-contract-address		Custom network core contract address
cn-feeder-url		Custom network feeder URL
cn-gateway-url		Custom network gateway URL
cn-l1-chain-id		Custom network L1 chain id
cn-l2-chain-id		Custom network L2 chain id
cn-name		Custom network name
cn-unverifiable-range	[]	Custom network range of blocks to skip hash verifications (e.g. 0,100)
colour	true	Use --colour=false command to disable colourized outputs (ANSI Escape Codes)
config		The YAML configuration file
db-cache-size	1024	Determines the amount of memory (in megabytes) allocated for caching data in the database
db-max-handles	1024	A soft limit on the number of open files that can be used by the DB
db-path	juno	Location of the database files
disable-l1-verification	false	Disables L1 verification since an Ethereum node is not provided
eth-node		WebSocket endpoint of the Ethereum node. To verify the correctness of the L2 chain, Juno must connect to an Ethereum node and parse events in the Starknet contract
grpc	false	Enable the HTTP gRPC server on the default port
grpc-host	localhost	The interface on which the gRPC server will listen for requests
grpc-port	6064	The port on which the gRPC server will listen for requests
gw-api-key		API key for gateway endpoints to avoid throttling
gw-timeout	5	Timeout for requests made to the gateway
http	false	Enables the HTTP RPC server on the default port and interface
http-host	localhost	The interface on which the HTTP RPC server will listen for requests
http-port	6060	The port on which the HTTP server will listen for requests
log-level	info	Options: trace, debug, info, warn, error
max-vm-queue	2 * max-vms	Maximum number for requests to queue after reaching max-vms before starting to reject incoming requests
max-vms	3 * CPU Cores	Maximum number for VM instances to be used for RPC calls concurrently
metrics	false	Enables the Prometheus metrics endpoint on the default port
metrics-host	localhost	The interface on which the Prometheus endpoint will listen for requests
metrics-port	9090	The port on which the Prometheus endpoint will listen for requests
network	mainnet	Options: mainnet, sepolia, sepolia-integration
p2p	false	EXPERIMENTAL: Enables p2p server
p2p-addr		EXPERIMENTAL: Specify p2p listening source address as multiaddr. Example: /ip4/0.0.0.0/tcp/7777
p2p-feeder-node	false	EXPERIMENTAL: Run juno as a feeder node which will only sync from feeder gateway and gossip the new blocks to the network
p2p-peers		EXPERIMENTAL: Specify list of p2p peers split by a comma. These peers can be either Feeder or regular nodes
p2p-private-key		EXPERIMENTAL: Hexadecimal representation of a private key on the Ed25519 elliptic curve
p2p-public-addr		EXPERIMENTAL: Specify p2p public address as multiaddr. Example: /ip4/35.243.XXX.XXX/tcp/7777
pending-poll-interval	5	Sets how frequently pending block will be updated (0s will disable fetching of pending block)
plugin-path		Path to the plugin .so file
pprof	false	Enables the pprof endpoint on the default port
pprof-host	localhost	The interface on which the pprof HTTP server will listen for requests
pprof-port	6062	The port on which the pprof HTTP server will listen for requests
remote-db		gRPC URL of a remote Juno node
rpc-call-max-steps	4000000	Maximum number of steps to be executed in starknet_call requests. The upper limit is 4 million steps, and any higher value will still be capped at 4 million
rpc-cors-enable	false	Enable CORS on RPC endpoints
rpc-max-block-scan	18446744073709551615	Maximum number of blocks scanned in single starknet_getEvents call
versioned-constants-file		Use custom versioned constants from provided file
ws	false	Enables the WebSocket RPC server on the default port
ws-host	localhost	The interface on which the WebSocket RPC server will listen for requests
ws-port	6061	The port on which the WebSocket server will listen for requests

Subcommands

Juno provides several subcommands to perform specific tasks or operations. Here are the available ones:

• genp2pkeypair: Generate a private key pair for p2p.
• db: Perform database-related operations
  • db info: Retrieve information about the database.
  • db size: Calculate database size information for each data type.
  • db revert: Reverts the database to a specific block number.

To use a subcommand, append it when running Juno:

# Running a subcommand
./build/juno <subcommand>

# Running the genp2pkeypair subcommand
./build/juno genp2pkeypair

# Running the db info subcommand
./build/juno db info