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authorKay Sievers <kay.sievers@suse.de>2005-11-17 18:05:29 +0100
committerKay Sievers <kay.sievers@suse.de>2005-11-17 18:05:29 +0100
commitdfc9761d8846a5f6f437fb599bc6817d14efbec2 (patch)
tree28619272104d9af53cecc59d3340e898158bb6a9 /README
parent82de5983ab395df7f59ed53a51517a6066be3a57 (diff)
update README
Signed-off-by: Kay Sievers <kay.sievers@suse.de>
Diffstat (limited to 'README')
-rw-r--r--README75
1 files changed, 46 insertions, 29 deletions
diff --git a/README b/README
index fee078898c..fe56095686 100644
--- a/README
+++ b/README
@@ -13,50 +13,58 @@ Important Note:
of "default" rules provided by the upstream udev version.
Requirements:
- - 2.6 version of the Linux kernel.
+ - 2.6.x version of the Linux kernel. See the RELEASE-NOTES file in the
+ udev tree and the Documentation/Changes in the kernel source tree for
+ the actual dependency.
- - The kernel must have sysfs, netlink, and hotplug enabled.
+ - The kernel must have sysfs and unix domain socket enabled.
+ (unix domain sockets (CONFIG_UNIX) as a loadable kernel module may work,
+ but it is completely silly, don't complain if anything goes wrong.)
- The proc filesystem must be mounted on /proc.
- The sysfs filesystem must be mounted at /sys. No other location
- is supported.
+ will be supported by udev.
Operation:
- - Udev creates and removes device nodes in /dev based on events
- the kernel sends out on device discovery or removal
+ Udev creates and removes device nodes in /dev, based on events the kernel
+ sends out on device discovery or removal.
- - Directly after mounting the root filesystem, the udevd daemon must be
- started by an init script.
+ - Directly after mouting the real root filesystem, wherever that
+ happens, in initramfs or with a directly mounted root, /dev should get
+ a tmpfs filesystem mounted, which is populated from scratch by udev.
+ Created nodes or changed permissions don't survive a reboot.
- - From kernel version 2.6.15 on, the hotplug helper /sbin/hotplug should
- be disabled with an init script before kernel modules are loaded.
+ - The content of /lib/udev/devices directory should be copied over to the
+ tmpfs mounted /dev, to provide the required nodes to initialize udev.
- - During bootup, /dev usually gets a tmpfs filesystem mounted which is
- populated from scratch by udev (created nodes don't survive a reboot,
- the /lib/udev/devices directory should be used for "static nodes").
+ - The udevd daemon must be started to receive netlink events from the kernel
+ driver core.
- - Udev replaces the hotplug event management invoked from /sbin/hotplug
- by the udevd daemon, which receives the kernel events over netlink.
+ - From kernel version 2.6.15 on, the hotplug helper /sbin/hotplug should
+ be disabled with an init script before the boot scripts are run and
+ kernel modules are loaded.
- - All kernel events are matched against a set of specified rules which
- make it possible to hook into the event processing.
+ - All kernel events are matched against a set of specified rules in
+ /etc/udev/rules.d/ which make it possible to hook into the event
+ processing to load required kernel modules and setup devices. For all
+ devices the kernel requests a device node, udev will create one with
+ the default name or the one specified by a matching udev rules.
- - Copies of the rules files for all major distros are in the etc/udev
- directory (you may look there how others distros are doing it).
Compile Options:
prefix
- Set this to the default root that you want to use only override
- this if you really know what you are doing even then, you probably
+ Set this to the default root that you want to use. Only override
+ this if you really know what you are doing, even then, you probably
don't do the right thing.
DESTDIR
Prefix for install target, used for package building.
USE_LOG
- if set to 'true', udev is able to pass errors or debug information
- to syslog. This is very useful to see what udev is doing or not doing,
- it is enabled by default.
+ If set to 'true', udev is able to pass errors or debug information
+ to syslog. This is very useful to see what udev is doing or not doing.
+ It is enabled by default, don't expect any useful answer, if you
+ need to hunt a bug, but you can't enable syslog.
DEBUG
If set to 'true', very verbose debugging messages will be compiled
into the udev binaries. The actual level of debugging is specified
@@ -75,20 +83,29 @@ Compile Options:
If set, will build the "extra" helper programs as specified
as listed (see below for an example).
-If you want to build the udev helper program cdrom_id and scsi_id:
- make EXTRAS="extras/cdrom_id extras/scsi_id"
+If you want to build the udev helper programs:
+ make EXTRAS="extras/cdrom_id extras/scsi_id extras/volume_id"
+
Installation:
- - The install target intall the udev binaries in the default locations,
- all at boot time reqired binaries will be installed in /sbin.
+ - The install target intalls the udev binaries in the default locations,
+ All at boot time reqired binaries will be installed in /sbin.
- The default location for scripts and binaries that are called from
- rules is /lib/udev.
+ rules is /lib/udev. Other packages who install udev rules, should use
+ that diretory too.
- It is recommended to use the /lib/udev/devices directory to place
device nodes and symlinks in, which are copied to /dev at every boot.
That way, nodes for broken subsystems or devices which can't be
- detected automatically by the kernel will always be available.
+ detected automatically by the kernel, will always be available.
+
+ - Copies of the rules files for all major distros are in the etc/udev
+ directory (you may look there how others distros are doing it).
+
+ - The persistent disk links in /dev/disk are the de facto standard
+ on Linux and should be installed with every default udev installation.
+ The devfs naming scheme rules are not recommended and not supported.
Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
linux-hotplug-devel@lists.sourceforge.net