udevadm(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | SEE ALSO | COLOPHON

UDEVADM(8)                       udevadm                      UDEVADM(8)

NAME         top

       udevadm - udev management tool

SYNOPSIS         top

       udevadm [--debug] [--version] [--help]

       udevadm info [options] [devpath]

       udevadm trigger [options] [devpath]

       udevadm settle [options]

       udevadm control option

       udevadm monitor [options]

       udevadm test [options] devpath

       udevadm test-builtin [options] command devpath

DESCRIPTION         top

       udevadm expects a command and command specific options. It
       controls the runtime behavior of systemd-udevd, requests kernel
       events, manages the event queue, and provides simple debugging
       mechanisms.

OPTIONS         top

       -d, --debug
           Print debug messages to standard error. This option is
           implied in udevadm test and udevadm test-builtin commands.

       -h, --help
           Print a short help text and exit.

   udevadm info [options] [devpath|file|unit...]
       Query the udev database for device information.

       Positional arguments should be used to specify one or more
       devices. Each one may be a device name (in which case it must
       start with /dev/), a sys path (in which case it must start with
       /sys/), or a systemd device unit name (in which case it must end
       with ".device", see systemd.device(5)).

       -q, --query=TYPE
           Query the database for the specified type of device data.
           Valid TYPEs are: name, symlink, path, property, all.

       -p, --path=DEVPATH
           The /sys/ path of the device to query, e.g.
           [/sys/]/class/block/sda. This option is an alternative to the
           positional argument with a /sys/ prefix.  udevadm info
           --path=/class/block/sda is equivalent to udevadm info
           /sys/class/block/sda.

       -n, --name=FILE
           The name of the device node or a symlink to query, e.g.
           [/dev/]/sda. This option is an alternative to the positional
           argument with a /dev/ prefix.  udevadm info --name=sda is
           equivalent to udevadm info /dev/sda.

       -r, --root
           Print absolute paths in name or symlink query.

       -a, --attribute-walk
           Print all sysfs properties of the specified device that can
           be used in udev rules to match the specified device. It
           prints all devices along the chain, up to the root of sysfs
           that can be used in udev rules.

       -x, --export
           Print output as key/value pairs. Values are enclosed in
           single quotes. This takes effects only when --query=property
           or --device-id-of-file=FILE is specified.

       -P, --export-prefix=NAME
           Add a prefix to the key name of exported values. This implies
           --export.

       -d, --device-id-of-file=FILE
           Print major/minor numbers of the underlying device, where the
           file lives on. If this is specified, all positional arguments
           are ignored.

       -e, --export-db
           Export the content of the udev database.

       -c, --cleanup-db
           Cleanup the udev database.

       -w[SECONDS], --wait-for-initialization[=SECONDS]
           Wait for device to be initialized. If argument SECONDS is not
           specified, the default is to wait forever.

       -h, --help
           Print a short help text and exit.

       The generated output shows the current device database entry in a
       terse format. Each line shown is prefixed with one of the
       following characters:

       Table 1. udevadm info output prefixes
       ┌───────┬─────────────────────────┐
       │Prefix Meaning                 │
       ├───────┼─────────────────────────┤
       │"P:"   │ Device path in /sys/    │
       ├───────┼─────────────────────────┤
       │"N:"   │ Kernel device node name │
       ├───────┼─────────────────────────┤
       │"L:"   │ Device node symlink     │
       │       │ priority                │
       ├───────┼─────────────────────────┤
       │"S:"   │ Device node symlink     │
       ├───────┼─────────────────────────┤
       │"E:"   │ Device property         │
       └───────┴─────────────────────────┘

   udevadm trigger [options] [devpath|file|unit]
       Request device events from the kernel. Primarily used to replay
       events at system coldplug time.

       Takes device specifications as positional arguments. See the
       description of info above.

       -v, --verbose
           Print the list of devices which will be triggered.

       -n, --dry-run
           Do not actually trigger the event.

       -q, --quiet
           Suppress error logging in triggering events.

       -t, --type=TYPE
           Trigger a specific type of devices. Valid types are: devices,
           subsystems. The default value is devices.

       -c, --action=ACTION
           Type of event to be triggered. Possible actions are "add",
           "remove", "change", "move", "online", "offline", "bind", and
           "unbind". Also, the special value "help" can be used to list
           the possible actions. The default value is "change".

       -s, --subsystem-match=SUBSYSTEM
           Trigger events for devices which belong to a matching
           subsystem. This option supports shell style pattern matching.
           When this option is specified more than once, then each
           matching result is ORed, that is, all the devices in each
           subsystem are triggered.

       -S, --subsystem-nomatch=SUBSYSTEM
           Do not trigger events for devices which belong to a matching
           subsystem. This option supports shell style pattern matching.
           When this option is specified more than once, then each
           matching result is ANDed, that is, devices which do not match
           all specified subsystems are triggered.

       -a, --attr-match=ATTRIBUTE=VALUE
           Trigger events for devices with a matching sysfs attribute.
           If a value is specified along with the attribute name, the
           content of the attribute is matched against the given value
           using shell style pattern matching. If no value is specified,
           the existence of the sysfs attribute is checked. When this
           option is specified multiple times, then each matching result
           is ANDed, that is, only devices which have all specified
           attributes are triggered.

       -A, --attr-nomatch=ATTRIBUTE=VALUE
           Do not trigger events for devices with a matching sysfs
           attribute. If a value is specified along with the attribute
           name, the content of the attribute is matched against the
           given value using shell style pattern matching. If no value
           is specified, the existence of the sysfs attribute is
           checked. When this option is specified multiple times, then
           each matching result is ANDed, that is, only devices which
           have none of the specified attributes are triggered.

       -p, --property-match=PROPERTY=VALUE
           Trigger events for devices with a matching property value.
           This option supports shell style pattern matching. When this
           option is specified more than once, then each matching result
           is ORed, that is, devices which have one of the specified
           properties are triggered.

       -g, --tag-match=TAG
           Trigger events for devices with a matching tag. When this
           option is specified multiple times, then each matching result
           is ANDed, that is, devices which have all specified tags are
           triggered.

       -y, --sysname-match=NAME
           Trigger events for devices for which the last component (i.e.
           the filename) of the /sys/ path matches the specified PATH.
           This option supports shell style pattern matching. When this
           option is specified more than once, then each matching result
           is ORed, that is, all devices which have any of the specified
           NAME are triggered.

       --name-match=NAME
           Trigger events for devices with a matching device path. When
           this option is specified more than once, then each matching
           result is ORed, that is, all specified devices are triggered.

       -b, --parent-match=SYSPATH
           Trigger events for all children of a given device. When this
           option is specified more than once, then each matching result
           is ORed, that is, all children of each specified device are
           triggered.

       -w, --settle
           Apart from triggering events, also waits for those events to
           finish. Note that this is different from calling udevadm
           settle.  udevadm settle waits for all events to finish. This
           option only waits for events triggered by the same command to
           finish.

       --uuid
           Trigger the synthetic device events, and associate a
           randomized UUID with each. These UUIDs are printed to
           standard output, one line for each event. These UUIDs are
           included in the uevent environment block (in the
           "SYNTH_UUID=" property) and may be used to track delivery of
           the generated events.

       --wait-daemon[=SECONDS]
           Before triggering uevents, wait for systemd-udevd daemon to
           be initialized. Optionally takes timeout value. Default
           timeout is 5 seconds. This is equivalent to invoke invoking
           udevadm control --ping before udevadm trigger.

       -h, --help
           Print a short help text and exit.

       In addition, optional positional arguments can be used to specify
       device names or sys paths. They must start with /dev/ or /sys/
       respectively.

   udevadm settle [options]
       Watches the udev event queue, and exits if all current events are
       handled.

       -t, --timeout=SECONDS
           Maximum number of seconds to wait for the event queue to
           become empty. The default value is 120 seconds. A value of 0
           will check if the queue is empty and always return
           immediately. A non-zero value will return an exit code of 0
           if queue became empty before timeout was reached, non-zero
           otherwise.

       -E, --exit-if-exists=FILE
           Stop waiting if file exists.

       -h, --help
           Print a short help text and exit.

       See systemd-udev-settle.service(8) for more information.

   udevadm control option
       Modify the internal state of the running udev daemon.

       -e, --exit
           Signal and wait for systemd-udevd to exit. No option except
           for --timeout can be specified after this option. Note that
           systemd-udevd.service contains Restart=always and so as a
           result, this option restarts systemd-udevd. If you want to
           stop systemd-udevd.service, please use the following:

               systemctl stop systemd-udevd-control.socket systemd-udevd-kernel.socket systemd-udevd.service

       -l, --log-level=value
           Set the internal log level of systemd-udevd. Valid values are
           the numerical syslog priorities or their textual
           representations: emerg, alert, crit, err, warning, notice,
           info, and debug.

       -s, --stop-exec-queue
           Signal systemd-udevd to stop executing new events. Incoming
           events will be queued.

       -S, --start-exec-queue
           Signal systemd-udevd to enable the execution of events.

       -R, --reload
           Signal systemd-udevd to reload the rules files and other
           databases like the kernel module index. Reloading rules and
           databases does not apply any changes to already existing
           devices; the new configuration will only be applied to new
           events.

       -p, --property=KEY=value
           Set a global property for all events.

       -m, --children-max=value
           Set the maximum number of events, systemd-udevd will handle
           at the same time.

       --ping
           Send a ping message to systemd-udevd and wait for the reply.
           This may be useful to check that systemd-udevd daemon is
           running.

       -t, --timeout=seconds
           The maximum number of seconds to wait for a reply from
           systemd-udevd.

       -h, --help
           Print a short help text and exit.

   udevadm monitor [options]
       Listens to the kernel uevents and events sent out by a udev rule
       and prints the devpath of the event to the console. It can be
       used to analyze the event timing, by comparing the timestamps of
       the kernel uevent and the udev event.

       -k, --kernel
           Print the kernel uevents.

       -u, --udev
           Print the udev event after the rule processing.

       -p, --property
           Also print the properties of the event.

       -s, --subsystem-match=string[/string]
           Filter kernel uevents and udev events by subsystem[/devtype].
           Only events with a matching subsystem value will pass. When
           this option is specified more than once, then each matching
           result is ORed, that is, all devices in the specified
           subsystems are monitored.

       -t, --tag-match=string
           Filter udev events by tag. Only udev events with a given tag
           attached will pass. When this option is specified more than
           once, then each matching result is ORed, that is, devices
           which have one of the specified tags are monitored.

       -h, --help
           Print a short help text and exit.

   udevadm test [options] [devpath]
       Simulate a udev event run for the given device, and print debug
       output.

       -a, --action=ACTION
           Type of event to be simulated. Possible actions are "add",
           "remove", "change", "move", "online", "offline", "bind", and
           "unbind". Also, the special value "help" can be used to list
           the possible actions. The default value is "add".

       -N, --resolve-names=early|late|never
           Specify when udevadm 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.

   udevadm test-builtin [options] [command] [devpath]
       Run a built-in command COMMAND for device DEVPATH, and print
       debug output.

       -a, --action=ACTION
           Type of event to be simulated. Possible actions are "add",
           "remove", "change", "move", "online", "offline", "bind", and
           "unbind". Also, the special value "help" can be used to list
           the possible actions. The default value is "add".

       -h, --help
           Print a short help text and exit.

SEE ALSO         top

       udev(7), systemd-udevd.service(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 2021-08-27.  (At that
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       (which is not part of the original manual page), send a mail to
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systemd 249                                                   UDEVADM(8)

Pages that refer to this page: systemd.link(5)udev.conf(5)systemd.net-naming-scheme(7)udev(7)dmsetup(8)lvmdump(8)systemd-udevd.service(8)systemd-udev-settle.service(8)