Configuration

S4 is configured through environment variables. All settings have sensible defaults for development.

Environment Variables

Variable	Description	Default
`S4_BIND`	Bind host address	`127.0.0.1`
`S4_DATA_DIR`	Base directory for storage data	System temp dir
`S4_ACCESS_KEY_ID`	Access key for S3 authentication	Auto-generated dev key
`S4_SECRET_ACCESS_KEY`	Secret key for S3 authentication	Auto-generated dev key
`S4_ROOT_USERNAME`	Root admin username	`root`
`S4_ROOT_PASSWORD`	Root admin password (enables IAM)	None (IAM disabled)
`S4_JWT_SECRET`	Secret key for signing JWT tokens	Auto-generated at startup
`S4_MAX_UPLOAD_SIZE`	Maximum upload size per request	`5GB`
`S4_TLS_CERT`	Path to TLS certificate (PEM)	None (HTTP mode)
`S4_TLS_KEY`	Path to TLS private key (PEM)	None (HTTP mode)
`S4_LIFECYCLE_ENABLED`	Enable lifecycle policy worker	`true`
`S4_LIFECYCLE_INTERVAL_HOURS`	Lifecycle evaluation interval	`24`
`S4_LIFECYCLE_DRY_RUN`	Dry-run mode (log without deleting)	`false`
`S4_METRICS_ENABLED`	Enable Prometheus metrics	`true`

Size Format

The S4_MAX_UPLOAD_SIZE variable supports human-readable size suffixes:

GB or G — gigabytes
MB or M — megabytes
KB or K — kilobytes
No suffix — bytes

Examples: 5GB, 100MB, 1024KB, 5368709120

Example: Development Setup

export S4_ACCESS_KEY_ID=myaccesskey
export S4_SECRET_ACCESS_KEY=mysecretkey
export S4_DATA_DIR=/tmp/s4-data

./target/release/s4-server

Example: Production Setup

export S4_BIND=0.0.0.0
export S4_DATA_DIR=/var/lib/s4
export S4_ROOT_PASSWORD=your-strong-password
export S4_JWT_SECRET=your-256-bit-crypto-random-string
export S4_TLS_CERT=/etc/ssl/certs/s4.pem
export S4_TLS_KEY=/etc/ssl/private/s4-key.pem
export S4_MAX_UPLOAD_SIZE=10GB

./target/release/s4-server

Optional Configuration File

You can also use a config.toml file:

[server]
bind = "0.0.0.0:9000"

[storage]
data_path = "/var/lib/s4/volumes"
metadata_path = "/var/lib/s4/metadata.redb"

[tuning]
inline_threshold = 4096  # 4KB — objects below this are stored inline in the database
volume_size_mb = 1024    # 1GB — maximum size of each append-only volume file
strict_sync = true       # fsync after every write