udevadm
Manage and monitor udev event subsystem
TLDR
Monitor all device events
Print uevents sent out by the kernel
Print device events after being processed by udev
List attributes of device /dev/sda
Reload all udev rules
Trigger all udev rules to run
Test an event run by simulating loading of /dev/sda
SYNOPSIS
udevadm [options] command
PARAMETERS
help
Display help text and exit.
version
Print version number and exit.
monitor
Listen to kernel udev events.
control
Request udev control functions. Available functions: reload_rules, trigger
trigger
Request udev to process events for matching devices.
settle
Wait for all udev events to be handled.
info
Query the udev database for device information.
test
Simulate a udev event without actually creating device nodes.
admdb
Tool to manage udev's database.
hwdb
Tool to manage hardware databases.
DESCRIPTION
udevadm is a command-line utility used to manage the udev event manager in Linux systems.
udev dynamically manages device nodes in the /dev directory, creating, removing, and renaming them based on hardware events.
udevadm allows you to query the udev database, trigger events, monitor device activity, and test udev rules.
It's a crucial tool for troubleshooting device-related issues, configuring persistent device naming, and understanding how udev interacts with the system's hardware.
Using udevadm is usually required for debugging the boot process.
CAVEATS
udevadm requires root privileges for most operations.
Incorrect use of udevadm can lead to device malfunctions or system instability.
EXAMPLES
udevadm monitor: Monitors device events in real-time.
udevadm info --attribute-walk --path=/sys/block/sda: Displays detailed information about the device /dev/sda by traversing its attributes.
udevadm trigger: Triggers udev events based on current kernel state.
udevadm control reload_rules: Reloads the udev rules from disk.
HISTORY
udev was created as a replacement for devfs, which had several limitations.
udev dynamically creates and manages device nodes, providing a more flexible and robust solution.
udevadm is the command-line tool for interacting with udev, allowing users to manage devices, monitor events, and troubleshoot issues.
It has become an integral part of modern Linux distributions, providing a standardized way to manage hardware devices.
SEE ALSO
udev(7)