Handling device files

Linux has had a long history of device managers. Initially, administrators needed to make sure that the device nodes were already present on the file system (/dev was part of the persisted file system). Gradually, more dynamic approaches were used for device management.

Nowadays, device files are managed through a combination of a pseudo file system (devtmpfs) and a user space device manager called udev. This device manager has been merged in systemd as well, becoming systemd-udevd.

Note

There are projects, such as eudev, which provide udev functionality without requiring systemd to be installed and enabled on the system.

The device manager listens on a kernel socket for kernel events. These events inform the device manager about detected or plugged-in devices (or the removal of such devices) and allow the device manager to take appropriate action. For udev, these actions are defined in udev rules.

Using udev rules

The main configuration of udev is handled through udev rules...