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)