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
