UDEVADM(8) udevadm UDEVADM(8)
NAME
udevadm - udev management tool
SYNOPSIS
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
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
-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.
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.
-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=PROPERTY
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.
--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.
-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-priority=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.
-h, --help
Print a short help text and exit.
SEE ALSO
udev(7), systemd-udevd.service(8)
systemd 245 UDEVADM(8)