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Documentation Index

Fetch the complete documentation index at: https://docs.microsandbox.dev/llms.txt

Use this file to discover all available pages before exploring further.

SSH gives a sandbox a familiar interface without putting an SSH daemon inside the guest. microsandbox speaks SSH on the host side, then forwards shells, remote commands, and SFTP file operations through the sandbox’s command and filesystem channels. Use it when you want existing SSH tools to work with a sandbox, or when you want SDK code to use SSH semantics while still going through microsandbox. There are two ways to connect:
  • Native sessions use the built-in microsandbox SSH client. No host ssh binary, TCP listener, or authorized key is required, which makes it the quickest path for a shell from msb or SSH semantics from the SDK.
  • External clients serve the sandbox as an SSH server so standard tools such as ssh, sftp, and ProxyCommand can connect.

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Native sessions

Native sessions keep the SSH protocol boundary but do not expose a listener. microsandbox creates an in-process SSH client/server pair over an in-memory stream, then forwards SSH channels to the sandbox.

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CLI

msb ssh devbox
msb ssh connect devbox
With no remote command, the CLI opens an interactive shell. With --, the remaining tokens become the SSH command string and run through the sandbox shell. 
msb ssh devbox -- uname -a
msb ssh devbox -- sh -lc "cd /app && npm test"
If a sandbox name collides with an SSH subcommand such as serve or authorize, use --name. Sandbox names are limited to 128 UTF-8 bytes: 
msb ssh --name serve
msb ssh --name authorize -- uptime

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SDK

let sb = Sandbox::start("devbox").await?;
let ssh = sb.ssh().connect().await?;

let output = ssh.exec("uname -a").await?;
println!("{}", String::from_utf8_lossy(&output.stdout));

ssh.close().await?;

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Interactive attach

SDK clients can attach the local terminal to an SSH shell. This requires a real terminal. 
let code = sb
    .ssh()
    .connect_with(|ssh| ssh.term("xterm-256color"))
    .await?
    .attach()
    .await?;

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SFTP

The native SSH client can open SFTP over the same SSH connection. 
let sftp = ssh.sftp().await?;
sftp.write("/tmp/hello.txt", b"hello").await?;
let data = sftp.read("/tmp/hello.txt").await?;
sftp.close().await?;

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External clients

External client mode exposes a sandbox as an SSH server for tools that already speak SSH. This is the closest match for normal SSH usage: authorize a public key, serve the sandbox, then connect with ssh or sftp.

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Authorize a key

msb ssh authorize --file ~/.ssh/id_ed25519.pub
msb ssh authorize --key "ssh-ed25519 AAAA... user@host"
cat ~/.ssh/id_ed25519.pub | msb ssh authorize --stdin
Keys are appended to <MSB_HOME>/ssh/authorized_keys. Existing keys are deduplicated by public-key material.

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TCP listener

msb ssh serve devbox
The default listener is 127.0.0.1:2222. 
ssh -p 2222 root@127.0.0.1
sftp -P 2222 root@127.0.0.1
Choose a different bind address or port when needed: 
msb ssh serve devbox --host 127.0.0.1 --port 2223
Binding to 0.0.0.0 exposes the SSH listener beyond the local machine. Keep the default loopback bind unless you intentionally want remote clients to connect.

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ProxyCommand

msb ssh serve --stdio carries a single SSH connection over stdin/stdout instead of a TCP listener. Point OpenSSH at it with ProxyCommand so any standard SSH tool can reach the sandbox by host alias, with no port to manage. Add an entry to your ~/.ssh/config:
~/.ssh/config
Host devbox.msb
  User root
  ProxyCommand msb ssh serve devbox --stdio
The Host value is the alias you connect to, and devbox is the sandbox name passed to msb ssh serve. No HostName or Port is needed, because OpenSSH runs the ProxyCommand to open the transport instead of dialing a socket. Once it is in place, the alias works with any OpenSSH-based tool: 
ssh devbox.msb
sftp devbox.msb
scp ./build.tar devbox.msb:/tmp/
rsync -av ./src/ devbox.msb:/app/
Editors that build on OpenSSH, such as VS Code Remote-SSH, connect to the devbox.msb host the same way.

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SDK server endpoints

The Rust SDK exposes the general form: prepare an SSH server endpoint, then pass each ordered duplex stream to serve(stream). 
let server = sandbox
    .ssh()
    .server_with(|ssh| ssh.sftp(true))
    .await?;

server.serve(stream).await?;
The TypeScript, Python, and Go SDKs expose stdio server helpers for process-bridge use cases. See the SDK reference pages for the exact language-specific surface. For exact SDK signatures, see the SSH reference for Rust, TypeScript, Python, or Go.