Union Directories

Union directories allow you to combine multiple sources into a single view, creating a merged namespace.

Creating Union Directories

You can create union directories by using multiple bind operations with different modes. The order of operations matters, as it determines the lookup priority.

Basic Example

frg bind -b /local/bin /bin
frg bind -a /backup/bin /bin

This creates a three-layer union:

/local/bin (highest priority)
Original /bin (middle priority)
/backup/bin (lowest priority)

Common Use Cases

Development Environment

Create a layered development environment:

frg bind -b /dev/override /usr
frg bind -a /dev/fallback /usr

This allows:

Development files to override system files
System files to serve as the default
Fallback files for missing components

Configuration Management

Manage multiple configuration sources:

frg bind -b /etc/custom /etc
frg bind -a /etc/defaults /etc

This creates a hierarchy where: