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.
--property=NAME
When showing device properties using the
--query=property option, limit display to properties specified in the
argument. The argument should be a comma-separated list of property names. If
not specified, all known properties are shown.
Added in version 250.
--value
When showing device properties using the
--query=property option, print only their values, and skip the property
name and "=".
Cannot be used together with -x/--export or
-P/--export-prefix.
Added in version 250.
-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.
This switch supports JSON output mode (see --json= below).
Note that because this switch generates multiple JSON objects, JSON-SEQ mode
is automatically enabled (RFC7464). (Note: tools such as jq[1]
natively support JSON-SEQ via the --seq switch.)
-t, --tree
Display a sysfs tree. This recursively iterates through
the sysfs hierarchy and displays it in a tree structure. If a path is
specified only the subtree below and its parent directories are shown. This
will show both device and subsystem items.
Added in version 251.
-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.
Added in version 243.
--subsystem-match[=SUBSYSTEM],
--subsystem-nomatch[=SUBSYSTEM]
When used with
--export-db, only show devices of
or not of the given subsystem respectively.
Added in version 255.
--attr-match[=FILE[=VALUE]],
--attr-nomatch[=FILE[=VALUE]]
When used with
--export-db, only show devices
matching or not matching the given attribute respectively.
Added in version 255.
--property-match[=KEY=VALUE]
When used with
--export-db, only show devices
matching the given property and value.
Added in version 255.
--tag-match[=TAG]
When used with
--export-db, only show devices with
the given tag.
Added in version 255.
--sysname-match[=NAME]
When used with
--export-db, only show devices with
the given "/sys" path.
Added in version 255.
--name-match[=NAME]
When used with
--export-db, only show devices with
the given name in "/dev".
Added in version 255.
--parent-match[=NAME]
When used with
--export-db, only show devices with
the given parent device.
Added in version 255.
--initialized-match, --initialized-nomatch
When used with
--export-db, only show devices that
are initialized or not initialized respectively.
Added in version 255.
--json=MODE
Shows output formatted as JSON. Expects one of
"short" (for the shortest possible output without any redundant
whitespace or line breaks), "pretty" (for a pretty version of the
same, with indentation and line breaks) or "off" (to turn off JSON
output, the default).
-h, --help
Print a short help text and exit.
--no-pager
Do not pipe output into a pager.
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/ |
| "M:" |
Device name in /sys/ (i.e. the last component of "P:") |
| "R:" |
Device number in /sys/ (i.e. the numeric suffix of the last component of
"P:") |
| "J:" |
Device ID |
| "U:" |
Kernel subsystem |
| "B:" |
Driver subsystem |
| "T:" |
Kernel device type within subsystem |
| "D:" |
Kernel device node major/minor |
| "I:" |
Network interface index |
| "N:" |
Kernel device node name |
| "L:" |
Device node symlink priority |
| "S:" |
Device node symlink |
| "Q:" |
Block device sequence number (DISKSEQ) |
| "V:" |
Attached driver |
| "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.
Added in version 248.
-t, --type=TYPE
Trigger a specific type of devices. Valid types are
"all", "devices", and "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".
--prioritized-subsystem=SUBSYSTEM[,SUBSYSTEM...]
Takes a comma separated list of subsystems. When
triggering events for devices, the devices from the specified subsystems and
their parents are triggered first. For example, if
--prioritized-subsystem=block,net, then firstly all block devices and
their parents are triggered, in the next all network devices and their parents
are triggered, and lastly the other devices are triggered. This option can be
specified multiple times, and in that case the lists of the subsystems will be
merged. That is,
--prioritized-subsystem=block
--prioritized-subsystem=net is equivalent to
--prioritized-subsystem=block,net.
Added in version 251.
-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.
Added in version 218.
-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.
--initialized-match, --initialized-nomatch
When
--initialized-match is specified, trigger
events for devices that are already initialized by
systemd-udevd, and
skip devices that are not initialized yet.
When --initialized-nomatch is specified, trigger events for
devices that are not initialized by systemd-udevd yet, and skip
devices that are already initialized.
Typically, it is essential that applications which intend to use
such a match, make sure a suitable udev rule is installed that sets at least
one property on devices that shall be matched. See also Initialized Devices
section below for more details.
Warning
--initialized-nomatch can potentially save a significant amount of time
compared to re-triggering all devices in the system and e.g. can be used to
optimize boot time. However, this is not safe to be used in a boot sequence in
general. Especially, when udev rules for a device depend on its parent devices
(e.g. "ATTRS" or "IMPORT{parent}" keys, see
udev(7)
for more details), the final state of the device becomes easily unstable with
this option.
Added in version 251.
-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.
Added in version 238.
--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.
Added in version 249.
--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 invoking
udevadm control --ping before
udevadm trigger.
Added in version 241.
-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. When 0 is specified, then the maximum is determined
based on the system resources.
--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.
Added in version 241.
-t, --timeout=seconds
The maximum number of seconds to wait for a reply from
systemd-udevd.
--load-credentials
When specified, the following credentials are used when
passed in:
udev.conf.*
These credentials should contain valid
udev.conf(5) configuration data. From each matching credential a
separate file is created. Example: a passed credential udev.conf.50-foobar
will be copied into a configuration file /run/udev/udev.conf.d/50-foobar.conf.
Added in version 256.
udev.rules.*
These credentials should contain valid
udev(7)
rules. From each matching credential a separate file is created. Example: a
passed credential udev.rules.50-foobar will be copied into a configuration
file /run/udev/rules.d/50-foobar.rules.
Added in version 256.
Note, this does not imply --reload option. So, if
systemd-udevd is already running, please consider to also specify
-reload to make the copied udev rules files used by
systemd-udevd.
Added in version 256.
-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|file|unit]¶
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.
Added in version 209.
-h, --help
Print a short help text and exit.
udevadm test-builtin [options] command [devpath|file|unit]¶
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".
Added in version 250.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
udevadm verify [options] [file] ...¶
Verify syntactic, semantic, and stylistic correctness of udev
rules files.
Positional arguments could be used to specify one or more files to
check. If no files are specified, the udev rules are read from the files
located in the same udev/rules.d directories that are processed by the udev
daemon.
The exit status is 0 if all specified udev rules files are
syntactically, semantically, and stylistically correct, and a non-zero error
code otherwise.
-N,
--resolve-names=early|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
never, names will never be resolved.
Added in version 254.
--root=PATH
When looking for udev rules files located in udev/rules.d
directories, operate on files underneath the specified root path
PATH.
Added in version 254.
--no-summary
Do not show summary.
Added in version 254.
--no-style
Ignore style issues. When specified, even if style issues
are found in udev rules files, the exit status is
0 if no syntactic or
semantic errors are found.
Added in version 254.
-h, --help
Print a short help text and exit.
udevadm wait [options] [device|syspath] ...¶
Wait for devices or device symlinks being created and initialized
by systemd-udevd. Each device path must start with "/dev/"
or "/sys/", e.g. "/dev/sda",
"/dev/disk/by-path/pci-0000:3c:00.0-nvme-1-part1",
"/sys/devices/pci0000:00/0000:00:1f.6/net/eth0", or
"/sys/class/net/eth0". This can take multiple devices. This may be
useful for waiting for devices being processed by systemd-udevd after
e.g. partitioning or formatting the devices.
-t, --timeout=SECONDS
Maximum number of seconds to wait for the specified
devices or device symlinks being created, initialized, or removed. The default
value is "infinity".
Added in version 251.
--initialized=BOOL
Check if
systemd-udevd initialized devices.
Defaults to true. When false, the command only checks if the specified devices
exist. Set false to this setting if there is no udev rules for the specified
devices, as the devices will never be considered as initialized in that case.
See Initialized Devices section below for more details.
Added in version 251.
--removed
When specified, the command wait for devices being
removed instead of created or initialized. If this is specified,
--initialized= will be ignored.
Added in version 251.
--settle
When specified, also watches the udev event queue, and
wait for all queued events being processed by
systemd-udevd.
Added in version 251.
-h, --help
Print a short help text and exit.
udevadm lock [options] [command] ...¶
udevadm lock takes an (advisory) exclusive lock on a block
device (or all specified devices), as per Locking Block Device
Access[2] and invokes a program with the locks taken. When the invoked
program exits the locks are automatically released and its return value is
propagated as exit code of udevadm lock.
This tool is in particular useful to ensure that
systemd-udevd.service(8) does not probe a block device while changes
are made to it, for example partitions created or file systems formatted.
Note that many tools that interface with block devices natively support
taking relevant locks, see for example sfdisk(8)'s --lock
switch.
The command expects at least one block device specified via
--device= or --backing=, and a command line to execute as
arguments.
--device=DEVICE, -d
DEVICE
Takes a path to a device node of the device to lock. This
switch may be used multiple times (and in combination with
--backing=)
in order to lock multiple devices. If a partition block device node is
specified the containing "whole" block device is automatically
determined and used for the lock, as per the specification. If multiple
devices are specified, they are deduplicated, sorted by the major/minor of
their device nodes and then locked in order.
This switch must be used at least once, to specify at least one
device to lock. (Alternatively, use --backing=, see below.)
Added in version 251.
--backing=PATH, -b
PATH
If a path to a device node is specified, identical to
--device=. However, this switch alternatively accepts a path to a
regular file or directory, in which case the block device of the file system
the file/directory resides on is automatically determined and used as if it
was specified with
--device=.
Added in version 251.
--timeout=SECS, -t
SECS
Specifies how long to wait at most until all locks can be
taken. Takes a value in seconds, or in the usual supported time units, see
systemd.time(7). If specified as zero the lock is attempted and if not
successful the invocation will immediately fail. If passed as
"infinity" (the default) the invocation will wait indefinitely until
the lock can be acquired. If the lock cannot be taken in the specified time
the specified command will not be executed and the invocation will fail.
Added in version 251.
--print, -p
Instead of locking the specified devices and executing a
command, just print the device paths that would be locked, and execute no
command. This command is useful to determine the "whole" block
device in case a partition block device is specified. The devices will be
sorted by their device node major number as primary ordering key and the minor
number as secondary ordering key (i.e. they are shown in the order they'd be
locked). Note that the number of lines printed here can be less than the
number of
--device= and
--backing= switches specified in case
these resolve to the same "whole" devices.
Added in version 251.
-h, --help
Print a short help text and exit.
