SYSTEMD-UDEVD.SERVICE(8)     systemd-udevd.service    SYSTEMD-UDEVD.SERVICE(8)

NAME
       systemd-udevd.service, systemd-udevd-control.socket, systemd-udevd-
       kernel.socket, systemd-udevd-varlink.socket, systemd-udevd - Device
       event managing daemon

SYNOPSIS
       systemd-udevd.service

       systemd-udevd-control.socket

       systemd-udevd-kernel.socket

       systemd-udevd-varlink.socket

       /usr/lib/systemd/systemd-udevd [--daemon] [--debug] [--children-max=]
				      [--exec-delay=] [--event-timeout=]
				      [--resolve-names=early|late|never]
				      [--version] [--help]

DESCRIPTION
       systemd-udevd listens to kernel uevents. For every event, systemd-udevd
       executes matching instructions specified in udev rules. See udev(7).

       The behavior of the daemon can be configured using udev.conf(5), its
       command line options, environment variables, and on the kernel command
       line, or changed dynamically with udevadm control.

OPTIONS
       -d, --daemon
	   Detach and run in the background.

	   Added in version 186.

       -D, --debug
	   Print debug messages to standard error.

	   Added in version 186.

       -c, --children-max=
	   Limit the number of events executed in parallel.

	   Added in version 186.

       -e, --exec-delay=
	   Delay the execution of each RUN{program} parameter by the given
	   number of seconds. This option might be useful when debugging
	   system crashes during coldplug caused by loading non-working kernel
	   modules.

	   Added in version 186.

       -t, --event-timeout=
	   Set the number of seconds to wait for events to finish. After this
	   time, the event will be terminated. The default is 180 seconds.

	   Added in version 216.

       -s, --timeout-signal=
	   Set the signal which systemd-udevd will send to forked off
	   processes after reaching event timeout. The setting can be
	   overridden at boot time with the kernel command line option
	   udev.timeout_signal=. Setting to SIGABRT may be helpful in order to
	   debug worker timeouts. Defaults to SIGKILL. Note that setting the
	   option on the command line overrides the setting from the
	   configuration file.

	   Added in version 246.

       -N, --resolve-names=
	   Specify when systemd-udevd should resolve names of users and
	   groups. When set to early (the default), names will be resolved
	   when the rules are parsed. When set to late, names will be resolved
	   for every event. When set to never, names will never be resolved
	   and all devices will be owned by root.

	   Added in version 186.

       -h, --help
	   Print a short help text and exit.

       --version
	   Print a short version string and exit.

KERNEL COMMAND LINE
       Parameters prefixed with "rd." will be read when systemd-udevd is used
       in an initrd, those without will be processed both in the initrd and on
       the host.

       udev.log_level=, rd.udev.log_level=
	   Set the log level.

	   Added in version 247.

       udev.trace[=BOOL], rd.udev.trace[=BOOL]
	   Enable/disable trace logging. When enabled, udev.log_level= will be
	   ignored, and "debug" level is assumed.

	   Added in version 258.

       udev.children_max=, rd.udev.children_max=
	   Limit the number of events executed in parallel.

	   Added in version 186.

       udev.exec_delay=, rd.udev.exec_delay=
	   Delay the execution of each RUN{program} parameter by the given
	   number of seconds. This option might be useful when debugging
	   system crashes during coldplug caused by loading non-working kernel
	   modules.

	   Added in version 186.

       udev.event_timeout=, rd.udev.event_timeout=
	   Wait for events to finish up to the given number of seconds. This
	   option might be useful if events are terminated due to kernel
	   drivers taking too long to initialize.

	   Added in version 216.

       udev.timeout_signal=, rd.udev.timeout_signal=
	   Specifies a signal that systemd-udevd will send to workers on
	   timeout. Note that kernel command line option overrides both the
	   setting in the configuration file and the one on the program
	   command line.

	   Added in version 246.

       udev.blockdev_read_only, rd.udev.blockdev_read_only
	   If specified, mark all physical block devices read-only as they
	   appear. Synthetic block devices (such as loopback block devices or
	   device mapper devices) are left as they are. This is useful to
	   guarantee that the contents of physical block devices remains
	   unmodified during runtime, for example to implement fully stateless
	   systems, for testing or for recovery situations where corrupted
	   file systems shall not be corrupted further through accidental
	   modification.

	   A block device may be marked writable again by issuing the blockdev
	   --setrw command, see blockdev(8) for details.

	   Added in version 246.

       net.ifnames=
	   Network interfaces are renamed to give them predictable names when
	   possible. It is enabled by default; specifying 0 disables it.

	   Added in version 199.

       net.naming_scheme=
	   Network interfaces are renamed to give them predictable names when
	   possible (unless net.ifnames=0 is specified, see above). With this
	   kernel command line option it is possible to pick a specific
	   version of this algorithm and override the default chosen at
	   compilation time. Expects one of the naming scheme identifiers
	   listed in systemd.net-naming-scheme(7), or "latest" to select the
	   latest scheme known (to this particular version of
	   systemd-udevd.service).

	   Note that selecting a specific scheme is not sufficient to fully
	   stabilize interface naming: the naming is generally derived from
	   driver attributes exposed by the kernel. As the kernel is updated,
	   previously missing attributes systemd-udevd.service is checking
	   might appear, which affects older name derivation algorithms, too.

	   Added in version 240.

       net.ifname_policy=policy1[,policy2,...][,MAC]
	   Specifies naming policies applied when renaming network interfaces.
	   Takes a list of policies and an optional MAC address separated with
	   comma. Each policy value must be one of the policies understood by
	   the NamePolicy= setting in .link files, e.g.	 "onboard" or "path".
	   See systemd.link(5) for more details. When the MAC address is
	   specified, the policies are applied to the interface which has the
	   address. When no MAC address is specified, the policies are applied
	   to all interfaces. This kernel command line argument can be
	   specified multiple times.

	   This argument is not directly read by systemd-udevd, but is instead
	   converted to a .link file by systemd-network-generator.service(8).
	   For this argument to take effect, systemd-network-generator.service
	   must be enabled.

	   Example:

	       net.ifname_policy=keep,kernel,path,slot,onboard,01:23:45:67:89:ab
	       net.ifname_policy=keep,kernel,path,slot,onboard,mac

	   This is mostly equivalent to creating the following .link files:

	       # 91-name-policy-with-mac.link
	       [Match]
	       MACAddress=01:23:45:67:89:ab

	       [Link]
	       NamePolicy=keep kernel path slot onboard
	       AlternativeNamePolicy=path slot onboard

	   and

	       # 92-name-policy-for-all.link
	       [Match]
	       OriginalName=*

	       [Link]
	       NamePolicy=keep kernel path slot onboard mac
	       AlternativeNamePolicy=path slot onboard mac

	   Added in version 250.

SEE ALSO
       udev.conf(5), udev(7), udevadm(8)

systemd 258					      SYSTEMD-UDEVD.SERVICE(8)