ceviche-rs

Service/daemon wrapper. Supports Windows, Linux (systemd) and macOS.

Where we install systemd units and why

The Challenge

Different Linux distributions place systemd unit files in different locations:

• Debian/Ubuntu and modern RHEL-based systems: /usr/lib/systemd/system/
• Older systems and some distributions: /lib/systemd/system/
• User-specific overrides: /etc/systemd/system/

Our Approach

This library detects the correct systemd unit directory at runtime using the following strategy:

1. Environment variable override (CEVICHE_SYSTEMD_UNITDIR): If set, this takes precedence over everything else. Use this when you need explicit control over where units are installed.

2. pkg-config detection: We query pkg-config --variable=systemdsystemunitdir systemd to get the distribution's preferred location. This works on most modern systems that have systemd development packages installed.

3. Fallback probing: If pkg-config is unavailable or doesn't return a result, we probe common directories in order:

   • /usr/lib/systemd/system
   • /lib/systemd/system

Caveats and Best Practices

⚠️ This isn't the ideal approach for packaged software.

If you're creating distribution packages (.deb, .rpm, etc.), you should:

• For Debian/Ubuntu: Use dh_installsystemd or manually install to ${prefix}/lib/systemd/system/
• For RPM-based systems: Use %{_unitdir} macro in your spec file
• Let the distribution's packaging tools determine the correct location

This runtime detection is a pragmatic compromise for applications that need to self-register as services without relying on package manager scripts. It works well for:

• Development and testing
• Self-contained applications
• Situations where you can't use distribution-specific packaging

Usage

By default, ceviche will detect and use the system unit directory. To override:

# Specify a custom location
export CEVICHE_SYSTEMD_UNITDIR=/etc/systemd/system
./your-application service register

Why Default to System Units?

We default to system units (/usr/lib/systemd/system/ or /lib/systemd/system/) rather than user units (/usr/lib/systemd/user/, ~/.config/systemd/user/, etc) because:

• Most services run system-wide
• System units are more common for daemon applications
• You can always override with CEVICHE_SYSTEMD_UNITDIR if you need user units