lakim

Sandboxing a coding agent with a dedicated Unix user (Linux, macOS, WSL)

Objective

Run a coding agent (Claude, Opencode) as a dedicated, unprivileged Unix user so that it can only touch the files we explicitly hand it:

• No access to your personal files — other users' home directories, dotfiles (SSH keys, shell history, GPG keys, etc.), and, on WSL, the Windows filesystem (/mnt/c, /mnt/d, …).
• No sudo, no package installation, no system-wide changes.
• No GitHub credentials — the agent can read and write code in its own workspace, but cannot push, pull, or open PRs. A human is always in the loop for anything that leaves the machine. To let the agent handle its own branches and PRs, loosen this with a fine-grained PAT scoped to a single repo — but it then lives inside the sandbox, so prompt injection can use it up to that scope. Keep it minimal.

lakim

module BoxView
  
  class SessionError < StandardError; end
  class GetError < StandardError; end
  class RetryError < StandardError
    attr_reader :retry_after

    def initialize(retry_after)
      @retry_after = retry_after
    end

lakim

One command to rule them all

sudo aptitude install apache2 apache2-prefork-dev autoconf bison build-essential \
clang curl dnsutils git-core imagemagick libc6-dev libcurl4-openssl-dev libffi-dev \
libmagickwand-dev libmysqlclient16 libmysqlclient16-dev libreadline6-dev libsqlite3-0 \
libsqlite3-dev libssl-dev libxml2 libxml2-dev libxslt-dev libxslt1.1 libxslt1-dev \
libyaml-dev mysql-client mysql-server openssl sqlite3 wget zlib1g zlib1g-dev 

lakim

This note will walk you though setting up and securing a Ubuntu 10.04 LTS then deploying a Rails application with mulit-stage deployment.

TODO:

• Add section for NGINX setup

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Server Setup