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.
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
SEE ALSO
udev.conf(5), udev(7), udevadm(8)
systemd 252 SYSTEMD-UDEVD.SERVICE(8)
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