The upstream udev project's set of default rules may require a most recent
-kernel release to work properly.
This is currently version 2.6.32.
+kernel release to work properly.
Tools and rules shipped by udev are not public API and may change at any time.
Never call any private tool in /usr/lib/udev from any external application; it
- Some architectures might need a later kernel, that supports accept4(),
or need to backport the accept4() syscall wiring in the kernel.
- - These options are needed:
+ - These options are required:
- These options might be needed:
- CONFIG_TMPFS_POSIX_ACL=y (user ACLs for device nodes)
CONFIG_BLK_DEV_BSG=y (SCSI devices)
+ CONFIG_TMPFS_POSIX_ACL=y (user ACLs for device nodes)
+ - The /dev directory needs the 'devtmpfs' filesystem mounted.
+ Udev only manages the permissions and ownership of the
+ kernel-provided device nodes, and possibly creates additional symlinks.
- - Udev does not work with the CONFIG_SYSFS_DEPRECATED* option.
+ - Udev requires /run to be writable, which is usually done by mounting a
- - Unix domain sockets (CONFIG_UNIX) as a loadable kernel module may work,
- but it is not supported.
+ - This version of udev does not work properly with the CONFIG_SYSFS_DEPRECATED*
- The deprecated hotplug helper /sbin/hotplug should be disabled in the
kernel configuration, it is not needed today, and may render the system
- Some udev extras have external dependencies like:
libacl, libglib2, usbutils, pciutils, and gperf.
+ libglib2, usbutils, pciutils, and gperf.
All these extras can be disabled with configure options.
- - At bootup, the /dev directory should get the 'devtmpfs' filesystem
- mounted. Udev manages the permissions and ownership of the kernel-created
- device nodes, and udev possibly creates additional symlinks. If needed, udev also
- works on an empty 'tmpfs' filesystem, but some device nodes like
- /dev/null, /dev/console, /dev/kmsg should be created before udevd is started.
- The udev daemon should be started to handle device events sent by the kernel.
During bootup, the events for already existing devices can be replayed, so
- that they are configured by udev. This is usually done by:
- udevadm trigger --action=add --type=subsystems
- udevadm trigger --action=add --type=devices
+ that they are configured by udev. The systemd service files contain the
+ needed commands to start the udev daemon and the coldplug sequence.
- Restarting the daemon never applies any rules to existing devices.
- - New/changed rule files are picked up automatically; there is no daemon
- restart or signal needed.
+ - New/changed rule files are picked up automatically; there is usually no
+ daemon restart or signal needed.
- Based on events the kernel sends out on device creation/removal, udev