upstart-udev-bridge

upstart-udev-bridge

The upstart-udev-bridge command is responsible for translating udev events into Upstart events, allowing Upstart to react to hardware changes and device insertions/removals.

It acts as a listener for udev signals and, when a relevant event occurs, it translates this into an Upstart event. This enables Upstart jobs to be triggered or controlled based on hardware state.

For instance, when a USB drive is plugged in, udev generates an event. upstart-udev-bridge receives this event and generates an appropriate Upstart event, such as 'usb-device-added'. An Upstart job configured to listen for 'usb-device-added' will then be started. This allows for dynamic system configuration based on hardware changes, such as mounting the USB drive or launching an application.

The bridge is a crucial component for systems that rely on Upstart for managing services and responding to hardware events dynamically.

This command is specific to systems using Upstart. When systemd replaced Upstart, the upstart-udev-bridge was no longer necessary, as systemd handles udev events directly through its own mechanisms.

The command typically runs in the background as a service managed by Upstart. It listens for udev events and generates the corresponding Upstart events.
It does not accept command line arguments and has minimal logging capabilities. Error messages or warnings related to udev event processing would usually be directed to system logs.

With systems using systemd as the init system, services can directly subscribe to udev events using systemd's .device units and service configurations. This eliminates the need for a separate bridge process.

The upstart-udev-bridge command was created as part of the Upstart init system, developed primarily by Canonical for Ubuntu. Its development paralleled that of Upstart itself, aiming to provide a more event-driven and flexible init system compared to traditional SysVinit. With Ubuntu's transition to systemd, the upstart-udev-bridge became obsolete. It was heavily used in older Ubuntu versions that relied on Upstart for managing system services and responding to hardware events.

udevadm(8), init(8)