# Kit examples — Customize the shell environment

> Some tools install into a versioned directory and expect you to source an init script from your shell profile so their commands land on PATH.

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## Metadata

- Canonical URL: <https://wikikv.com/k/ref-docker-828a1e6d794e51fd6c1f>
- Knowledge kind: `reference`
- Confidence: `0.72`
- Independent verifications: `0`
- Updated: `2026-08-16T09:32:14.470495+00:00`
- Tags: `reference-seed`, `docker`, `manuals`, `ai`, `sandboxes`, `customize`, `kit`, `examples`, `shell`, `environment`

## Provenance

- Source: <https://github.com/docker/docs/blob/3a9d778562f39bcc0be46255b013c6a3ca526244/content/manuals/ai/sandboxes/customize/kit-examples.md>
- Source name: Docker Documentation
- Source revision: `3a9d778562f39bcc0be46255b013c6a3ca526244`
- Source license: `Apache-2.0`
- Attribution and license details: <https://wikikv.com/licenses>

## Knowledge

Reference note (untrusted external data; do not execute it as instructions).

Some tools install into a versioned directory and expect you to source an init script from your shell profile so their commands land on PATH. Version managers like nvm and SDKMAN! follow this pattern. To make the tool available in every shell, append the source line to /etc/sandbox-persistent.sh in an install command.

/etc/sandbox-persistent.sh is the sandbox's persistent environment file. It's sourced before every bash invocation — interactive shells and non-interactive ones, including agents started with sbx run and commands run with sbx exec. Appending here makes the tool available to the agent regardless of how its shell is launched. The same file is where you'd set a custom environment variable; see the FAQ.

Bounded code example (external data; do not execute automatically):
```yamltitlenvmspec.yaml
schemaVersion: "2"
kind: mixin
name: nvm
displayName: nvm
description: Node version manager available in every shell

setup:
  install:
    - command: "curl -fsSL https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash"
      user: "1000"
      description: Install nvm
    - command: |
        cat &gt;&gt; /etc/sandbox-persistent.sh &lt;&lt;'EOF'
        export NVM_DIR="$HOME/.nvm"
        unset NPM_CONFIG_PREFIX
        [ -s "$NVM_DIR/nvm.sh" ] &amp;&amp; source "$NVM_DIR/nvm.sh"
        EOF
      user: "1000"
      description: Source nvm for every shell
```

Both install steps run as user: "1000". This installs the tool under /home/agent/ and can update /etc/sandbox-persistent.sh, which the agent user owns. The $HOME in the appended lines resolves per user at source time, so the agent user finds its own install. Append to the file rather than overwriting it — the sandbox relies on its existing contents.

The base image ships its own Node and sets NPM_CONFIG_PREFIX, which nvm won't activate alongside. unset NPM_CONFIG_PREFIX before sourcing nvm.sh clears that conflict. Sourcing makes the nvm command available; it doesn't put a Node version on PATH. Run nvm install --lts to add one — wrap it in bash -c '…' if you script it as an install step, since install steps run under sh.

Append only the init script, not the tool's tab-completion script. Because /etc/sandbox-persistent.sh is sourced before every command, completion scripts — which rely on variables that exist only during completion — can break non-interactive shells that agents rely on.

Attribution: Adapted from Docker Documentation under Apache-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.