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96 lines
3.8 KiB
Plaintext
96 lines
3.8 KiB
Plaintext
udev - userspace device management
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For more information see the files in the docs/ directory.
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Important Note:
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Integrating udev in the system is a whole lot of work, has complex dependencies
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and differs a lot from distro to distro. All reasonable distros depend on udev
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these days and the system will not work without it.
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The upstream udev project does not support or recomend to replace a distro's udev
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installation with the upstream version. The installation of a unmodified upstream
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version may render your system unusable! There is no "default" setup or a set
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of "default" rules provided by the upstream udev version.
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Requirements:
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- 2.6 version of the Linux kernel.
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- The kernel must have sysfs, netlink, and hotplug enabled.
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- The proc filesystem must be mounted on /proc.
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- The sysfs filesystem must be mounted at /sys. No other location
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is supported.
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Operation:
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- Udev creates and removes device nodes in /dev based on events
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the kernel sends out on device discovery or removal
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- Directly after mounting the root filesystem, the udevd daemon must be
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started by an init script.
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- From kernel version 2.6.15 on, the hotplug helper /sbin/hotplug should
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be disabled with an init script before kernel modules are loaded.
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- During bootup, /dev usually gets a tmpfs filesystem mounted which is
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populated from scratch by udev (created nodes don't survive a reboot,
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the /lib/udev/devices directory should be used for "static nodes").
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- Udev replaces the hotplug event management invoked from /sbin/hotplug
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by the udevd daemon, which receives the kernel events over netlink.
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- All kernel events are matched against a set of specified rules which
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make it possible to hook into the event processing.
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- Copies of the rules files for all major distros are in the etc/udev
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directory (you may look there how others distros are doing it).
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Compile Options:
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prefix
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Set this to the default root that you want to use only override
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this if you really know what you are doing even then, you probably
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don't do the right thing.
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DESTDIR
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Prefix for install target, used for package building.
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USE_LOG
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if set to 'true', udev is able to pass errors or debug information
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to syslog. This is very useful to see what udev is doing or not doing,
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it is enabled by default.
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DEBUG
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If set to 'true', very verbose debugging messages will be compiled
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into the udev binaries. The actual level of debugging is specified
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in the udev config file.
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STRIPCMD
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If udev is compiled for packaging an empty string can be passed
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to disable the stripping of the binaries.
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USE_SELINUX
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If set to 'true', udev will be built with SELinux support
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enabled. This is disabled by default.
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USE_KLIBC
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If set to 'true', udev is built and linked against klibc.
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Default value is 'false'. KLCC specifies the klibc compiler
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wrapper, usually located at /usr/bin/klcc.
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EXTRAS
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If set, will build the "extra" helper programs as specified
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as listed (see below for an example).
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If you want to build the udev helper program cdrom_id and scsi_id:
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make EXTRAS="extras/cdrom_id extras/scsi_id"
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Installation:
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- The install target intall the udev binaries in the default locations,
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all at boot time reqired binaries will be installed in /sbin.
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- The default location for scripts and binaries that are called from
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rules is /lib/udev.
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- It is recommended to use the /lib/udev/devices directory to place
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device nodes and symlinks in, which are copied to /dev at every boot.
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That way, nodes for broken subsystems or devices which can't be
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detected automatically by the kernel will always be available.
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Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
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linux-hotplug-devel@lists.sourceforge.net
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