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CONFIGURATION
udev configuration files are placed in /etc/udev/ and /lib/udev/. All empty lines, or lines beginning with '#' will be
ignored.
Configuration file
udev expects its main configuration file at /etc/udev/udev.conf. It consists of a set of variables allowing the user to
override default udev values. The following variables can be set:
udev_root
Specifies where to place the device nodes in the filesystem. The default value is /dev.
udev_log
The logging priority. Valid values are the numerical syslog priorities or their textual representations: err, info
and debug.
Rules files
The udev rules are read from the files located in the default rules directory /lib/udev/rules.d/, the custom rules
directory /etc/udev/rules.d/ and the temporary rules directory /dev/.udev/rules.d/. All rule files are sorted and
processed in lexical order, regardless in which of these directories they live. Files in /etc/udev/rules.d/ have
precedence over files with the same name in /lib/udev/rules.d/. This can be used to ignore a default rules file if
needed.
Rule files must end in .rules, other extensions are ignored.
Every line in the rules file contains at least one key value pair. There are two kind of keys, match and assignment
keys. If all match keys are matching against its value, the rule gets applied and the assign keys get the specified
value assigned.
A matching rule may rename a network interface, add symlinks pointing to the device node, or run a specified program as
part of the event handling.
A rule consists of a list of one or more key value pairs separated by a comma. Each key has a distinct operation,
depending on the used operator.
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