Getting started

This guide gets you from zero to a running Selium service on your machine. You will:

Install the Selium runtime and CLI.
Build a tiny WASM service.
Start a local runtime (with the remote client enabled).
Launch your service and attach to its logs.

Prerequisites

You will need stable Rust (see rustup.rs), plus the WebAssembly target:

rustup target add wasm32-unknown-unknown

1. Install the runtime and CLI

We recommend using the install script to install selium-runtime (server) and selium (CLI):

curl --proto '=https' --tlsv1.2 -sSfL https://selium.com/install.sh | sh

From source

You can also build from source:

git clone https://github.com/seliumlabs/selium
cd selium
 
cargo build -p selium-runtime --release
 
git clone https://github.com/seliumlabs/selium-modules
 
cd selium-modules/remote-client
cargo build -p selium-remote-client-server --target wasm32-unknown-unknown --release
 
cd ../switchboard
cargo build -p selium-switchboard-server --target wasm32-unknown-unknown --release
 
cd ../atlas
cargo build -p selium-atlas-server --target wasm32-unknown-unknown --release

You'll also need to create a work directory and generate some TLS certificates:

mkdir -p selium-work/{certs,modules}
selium-runtime generate-certs --output-dir selium-work/certs

The certificates are used to secure the local QUIC server, which the CLI uses to talk to the runtime.

The work directory holds two groups of important files:

selium-work/certs for TLS certificates
selium-work/modules for WASM modules (your apps and system modules)

2. Create a service

src/lib.rs:

use selium_userland::entrypoint;
use tracing::info;
 
#[entrypoint]
fn hello() {
    info!("hello from selium");
}

Cargo.toml:

[package]
name = "hello"
version = "0.1.0"
edition = "2024"
 
[lib]
crate-type = ["cdylib"]
 
[dependencies]
selium-userland = "1.0.0-alpha.5"
tracing = "0.1"

Build to WASM and copy into the work dir:

cargo build --release --target wasm32-unknown-unknown
cp target/wasm32-unknown-unknown/release/hello.wasm selium-work/modules/

3. Start the runtime in the background

The below command will start a new Selium runtime instance, preloading the Remote Client, Switchboard, and Atlas modules. These modules add extra functionality on top of the core platform. Generally you'll need the Remote Client for CLI access, but the Switchboard and Atlas can be omitted for a leaner runtime. See the echo-no-deps example for details.

For this guide, we'll assume you're using all three.

selium-runtime --work-dir selium-work \
  --module 'path=selium_remote_client_server.wasm;capabilities=ChannelLifecycle,ChannelReader,ChannelWriter,ProcessLifecycle,NetQuicBind,NetQuicAccept,NetQuicRead,NetQuicWrite;args=utf8:localhost,u16:7000' \
  --module 'path=selium_switchboard_server.wasm;capabilities=ChannelLifecycle,ChannelReader,ChannelWriter,SingletonRegistry' \
  --module 'path=selium_atlas_server.wasm;capabilities=ChannelLifecycle,ChannelReader,ChannelWriter,SingletonRegistry' &

4. Start your service with the CLI

Start your example application with required capabilities. These are required for creating a channel to publish logs to (ChannelLifecycle), and writing to that channel (ChannelWriter).

selium --cert-dir selium-work/certs \
  start hello.wasm start \
  --capabilities ChannelLifecycle,ChannelWriter \
  --attach

The CLI will print out the process's system ID, which you can use to stop it later:

Started process (id=...)

selium --cert-dir selium-work/certs stop <id>

Next steps

Read Applications next to understand entrypoints, arguments, and capability grants.
If you want typed messaging and discovery, add Switchboard and Atlas to your mental model early.