Organize filesystem hierarchy following Unix FHS conventions

[pbalduino]

Summary

Establish a proper filesystem hierarchy standard (FHS) for meniOS, separating user executables, system binaries, and other directories following Unix conventions.

Current State

• All executables currently live in /bin
• No distinction between user programs, system utilities, and administrative tools
• As the OS grows, this flat structure becomes harder to maintain
• Package installation and system organization will become problematic

Proposed Directory Structure

Essential System Binaries

• /bin - Essential user command binaries (used by all users)

  • Examples: sh, cat, echo, ls, ps, kill
  • Available in single-user mode
  • Required for basic system operation

• /sbin - Essential system binaries (system administration)

  • Examples: init, mount, fsck, reboot
  • Typically require root privileges
  • Critical for system boot and recovery

User Programs

• /usr/bin - User command binaries (non-essential)

  • Examples: grep, xargs, env, utilities
  • Most user programs go here
  • Not needed for system boot/recovery

• /usr/sbin - Non-essential system administration binaries

  • Examples: package managers, network daemons
  • System tools not needed for boot

Local Additions

• /usr/local/bin - Locally compiled/installed user programs

  • User-compiled software
  • Third-party applications
  • TCC/GCC compiled programs

• /usr/local/sbin - Locally installed system administration programs

Other Important Directories

• /lib - Essential shared libraries and kernel modules
• /usr/lib - Libraries for /usr/bin and /usr/sbin
• /etc - System-wide configuration files
• /home - User home directories
• /tmp - Temporary files (already exists as tmpfs)
• /var - Variable data (logs, caches, runtime data)
  • /var/log - Log files
  • /var/tmp - Temporary files that persist across reboots
  • /var/run or /run - Runtime variable data (PID files, sockets)
• /opt - Optional/add-on application packages
• /usr/share - Architecture-independent data
  • /usr/share/doc - Documentation
  • /usr/share/man - Manual pages
  • /usr/share/zoneinfo - Timezone database (for #299)

Migration Strategy

Phase 1: Create Directory Structure

• Create all standard directories at boot
• Update init to create the full hierarchy
• Ensure proper permissions on each directory

Phase 2: Categorize Existing Binaries

Current /bin contents to categorize:

• Essential /bin: cat, echo, env, true, false, ps, kill, sh (mosh)
• Move to /usr/bin: grep (#234), xargs (#235), mem (#243)
• Move to /sbin: init (if not already separate)
• Move to /usr/sbin: System utilities as they're developed

Phase 3: Update Build System

• Modify userland/Makefile to install to correct directories
• Update INSTALL_DIR paths for each binary
• Add installation rules for /usr/bin, /sbin, /usr/sbin

Phase 4: Update PATH Environment

• Default PATH should include: /bin:/usr/bin:/usr/local/bin
• Root PATH should add: /sbin:/usr/sbin:/usr/local/sbin
• Update shell initialization in init (#180)

Phase 5: Documentation

• Document the filesystem hierarchy in docs/architecture/
• Update build documentation with installation paths
• Create guidelines for where new programs should be installed

Benefits

• Organization: Clear separation of concerns
• Security: Distinguish privileged system tools
• Standards: Follow Unix conventions for familiarity
• Scalability: Easier to manage as OS grows
• Package Management: Foundation for future package manager (#259)
• Native Compilation: Clear installation paths for locally compiled software (#190, #191)

Implementation Considerations

• Backward compatibility: maintain symlinks during transition?
• Shell PATH updates needed
• Build system changes required
• Documentation updates

Dependencies

• No hard dependencies, but benefits:
  • #180 (Environment seeding in init) ✅ - can update PATH
  • #259 (Package management database) - will use this structure
  • #190/#191 (TCC/binutils) - will install to /usr/local/bin

Priority

Medium - Important for long-term maintainability, but not blocking current work

Related Standards

• Filesystem Hierarchy Standard (FHS 3.0)
• POSIX directory structure
• Common Unix conventions (BSD, Linux, etc.)