Manual: systemd-udevd-kernel.socket

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 259.5									    SYSTEMD-UDEVD.SERVICE(8)