1SYSTEMD-UDEVD.SERVICE(8)     systemd-udevd.service    SYSTEMD-UDEVD.SERVICE(8)
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NAME

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

10       systemd-udevd.service
11
12       systemd-udevd-control.socket
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14       systemd-udevd-kernel.socket
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16       /usr/lib/systemd/systemd-udevd [--daemon] [--debug] [--children-max=]
17                                      [--exec-delay=] [--event-timeout=]
18                                      [--resolve-names=early|late|never]
19                                      [--version] [--help]
20

DESCRIPTION

22       systemd-udevd listens to kernel uevents. For every event, systemd-udevd
23       executes matching instructions specified in udev rules. See udev(7).
24
25       The behavior of the daemon can be configured using udev.conf(5), its
26       command line options, environment variables, and on the kernel command
27       line, or changed dynamically with udevadm control.
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OPTIONS

30       -d, --daemon
31           Detach and run in the background.
32
33       -D, --debug
34           Print debug messages to standard error.
35
36       -c, --children-max=
37           Limit the number of events executed in parallel.
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39       -e, --exec-delay=
40           Delay the execution of each RUN{program} parameter by the given
41           number of seconds. This option might be useful when debugging
42           system crashes during coldplug caused by loading non-working kernel
43           modules.
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45       -t, --event-timeout=
46           Set the number of seconds to wait for events to finish. After this
47           time, the event will be terminated. The default is 180 seconds.
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49       -s, --timeout-signal=
50           Set the signal which systemd-udevd will send to forked off
51           processes after reaching event timeout. The setting can be
52           overridden at boot time with the kernel command line option
53           udev.timeout_signal=. Setting to SIGABRT may be helpful in order to
54           debug worker timeouts. Defaults to SIGKILL. Note that setting the
55           option on the command line overrides the setting from the
56           configuration file.
57
58       -N, --resolve-names=
59           Specify when systemd-udevd should resolve names of users and
60           groups. When set to early (the default), names will be resolved
61           when the rules are parsed. When set to late, names will be resolved
62           for every event. When set to never, names will never be resolved
63           and all devices will be owned by root.
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65       -h, --help
66           Print a short help text and exit.
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68       --version
69           Print a short version string and exit.
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KERNEL COMMAND LINE

72       Parameters prefixed with "rd." will be read when systemd-udevd is used
73       in an initrd, those without will be processed both in the initrd and on
74       the host.
75
76       udev.log_level=, rd.udev.log_level=
77           Set the log level.
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79       udev.children_max=, rd.udev.children_max=
80           Limit the number of events executed in parallel.
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82       udev.exec_delay=, rd.udev.exec_delay=
83           Delay the execution of each RUN{program} parameter by the given
84           number of seconds. This option might be useful when debugging
85           system crashes during coldplug caused by loading non-working kernel
86           modules.
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88       udev.event_timeout=, rd.udev.event_timeout=
89           Wait for events to finish up to the given number of seconds. This
90           option might be useful if events are terminated due to kernel
91           drivers taking too long to initialize.
92
93       udev.timeout_signal=, rd.udev.timeout_signal=
94           Specifies a signal that systemd-udevd will send to workers on
95           timeout. Note that kernel command line option overrides both the
96           setting in the configuration file and the one on the program
97           command line.
98
99       udev.blockdev_read_only, rd.udev.blockdev_read_only
100           If specified, mark all physical block devices read-only as they
101           appear. Synthetic block devices (such as loopback block devices or
102           device mapper devices) are left as they are. This is useful to
103           guarantee that the contents of physical block devices remains
104           unmodified during runtime, for example to implement fully stateless
105           systems, for testing or for recovery situations where corrupted
106           file systems shall not be corrupted further through accidental
107           modification.
108
109           A block device may be marked writable again by issuing the blockdev
110           --setrw command, see blockdev(8) for details.
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112       net.ifnames=
113           Network interfaces are renamed to give them predictable names when
114           possible. It is enabled by default; specifying 0 disables it.
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116       net.naming-scheme=
117           Network interfaces are renamed to give them predictable names when
118           possible (unless net.ifnames=0 is specified, see above). With this
119           kernel command line option it is possible to pick a specific
120           version of this algorithm and override the default chosen at
121           compilation time. Expects one of the naming scheme identifiers
122           listed in systemd.net-naming-scheme(7), or "latest" to select the
123           latest scheme known (to this particular version of
124           systemd-udevd.service).
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126           Note that selecting a specific scheme is not sufficient to fully
127           stabilize interface naming: the naming is generally derived from
128           driver attributes exposed by the kernel. As the kernel is updated,
129           previously missing attributes systemd-udevd.service is checking
130           might appear, which affects older name derivation algorithms, too.
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132       net.ifname-policy=policy1[,policy2,...][,MAC]
133           Specifies naming policies applied when renaming network interfaces.
134           Takes a list of policies and an optional MAC address separated with
135           comma. Each policy value must be one of the policies understood by
136           the NamePolicy= setting in .link files, e.g.  "onboard" or "path".
137           See systemd.link(5) for more details. When the MAC address is
138           specified, the policies are applied to the interface which has the
139           address. When no MAC address is specified, the policies are applied
140           to all interfaces. This kernel command line argument can be
141           specified multiple times.
142
143           This argument is not directly read by systemd-udevd, but is instead
144           converted to a .link file by systemd-network-generator.service(8).
145           For this argument to take effect, systemd-network-generator.service
146           must be enabled.
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148           Example:
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150               net.ifname-policy=keep,kernel,path,slot,onboard,01:23:45:67:89:ab
151               net.ifname-policy=keep,kernel,path,slot,onboard,mac
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153           This is mostly equivalent to creating the following .link files:
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155               # 91-name-policy-with-mac.link
156               [Match]
157               MACAddress=01:23:45:67:89:ab
158
159               [Link]
160               NamePolicy=keep kernel path slot onboard
161               AlternativeNamePolicy=path slot onboard
162
163           and
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165               # 92-name-policy-for-all.link
166               [Match]
167               OriginalName=*
168
169               [Link]
170               NamePolicy=keep kernel path slot onboard mac
171               AlternativeNamePolicy=path slot onboard mac
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SEE ALSO

175       udev.conf(5), udev(7), udevadm(8)
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177
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179systemd 253                                           SYSTEMD-UDEVD.SERVICE(8)
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