systemd-udevd.service(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | KERNEL COMMAND LINE | SEE ALSO | COLOPHON

SYSTEMD-UDEVD.SERVICE(8)  systemd-udevd.service SYSTEMD-UDEVD.SERVICE(8)

NAME         top

       systemd-udevd.service, systemd-udevd-control.socket, systemd-
       udevd-kernel.socket, systemd-udevd - Device event managing daemon

SYNOPSIS         top

       systemd-udevd.service

       systemd-udevd-control.socket

       systemd-udevd-kernel.socket

       /usr/lib/systemd/systemd-udevd [--daemon] [--debug]
                                      [--children-max=] [--exec-delay=]
                                      [--event-timeout=]
                                      [--resolve-names=early|late|never]
                                      [--version] [--help]

DESCRIPTION         top

       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         top

       -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 RUN instructions 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         top

       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 RUN instructions 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         top

       udev.conf(5), udev(7), udevadm(8)

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have
       a bug report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2020-12-18.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2020-12-18.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

systemd 247                                     SYSTEMD-UDEVD.SERVICE(8)

Pages that refer to this page: sd-hwdb(3)sd_hwdb_get(3)sd_hwdb_new(3)systemd.exec(5)systemd.link(5)udev.conf(5)file-hierarchy(7)kernel-command-line(7)systemd.directives(7)systemd.index(7)systemd.net-naming-scheme(7)udev(7)systemd-network-generator.service(8)systemd-vconsole-setup.service(8)udevadm(8)