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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 - Device event managing daemon
SYNOPSIS
systemd-udevd.service
systemd-udevd-control.socket
systemd-udevd-kernel.socket
/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.
-D, --debug
Print debug messages to standard error.
-c, --children-max=
Limit the number of events executed in parallel.
-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.
-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.
-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.
-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.
-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.
udev.children_max=, rd.udev.children_max=
Limit the number of events executed in parallel.
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.
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.
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.
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.
net.ifnames=
Network interfaces are renamed to give them predictable names when possible. It is
enabled by default; specifying 0 disables it.
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.
SEE ALSO
udev.conf(5), udev(7), udevadm(8)
systemd 249 SYSTEMD-UDEVD.SERVICE(8)
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