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The systemd System and Service Manager
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Kay Sievers 12a7c14b86 rules: add SUBSYSTEM match to scsi rules 
On Fri, May 22, 2009 at 16:15, Alan Jenkins <alan-jenkins@tuffmail.co.uk> wrote:
> I've been looking at what is responsible for all the path lookup activity in
> coldplug.  On my debian stable system, it looks like every device gets its
> parent looked up in sysfs.  I think this is due to SUBSYSTEMS matches.
>
> I see the udev default rules are different, but it looks like they still
> test for SUBSYSTEMS on every single device. Should we add SUBSYSTEM="scsi_generic"
> to these three rules?
2009-05-22 16:44:53 +02:00
docs/writing_udev_rules doc: writing udev rules - refer to 'udevadm info' instead of 'udevinfo' 2009-01-24 15:24:01 +01:00
extras edd_id: use openat() 2009-05-20 18:10:26 +02:00
m4 add m4/ subdir 2009-02-26 14:11:43 +01:00
rules rules: add SUBSYSTEM match to scsi rules 2009-05-22 16:44:53 +02:00
test use more efficient string copying 2009-05-20 17:57:52 +02:00
udev udevadm: settle - make --timeout=0 working 2009-05-21 23:49:53 +02:00
.gitignore gitignore: move *.8 to subdirs 2008-09-29 05:03:43 +02:00
autogen.sh autogen.sh: add more warnings 2009-02-05 19:01:27 +01:00
ChangeLog release 142 2009-05-13 02:35:37 +02:00
configure.ac udevd: implement a more efficient queue file format 2009-05-21 22:22:37 +02:00
COPYING update source file headers 2006-08-28 00:29:11 +02:00
INSTALL update INSTALL 2008-08-28 22:58:03 +02:00
Makefile.am add m4/ subdir 2009-02-26 14:11:43 +01:00
Makefile.am.inc libudev: get rid of selinux 2008-10-02 18:48:40 +02:00
NEWS update NEWS 2009-05-21 23:52:09 +02:00
README update NEWS 2009-01-04 17:38:33 +01:00
TODO update TODO 2009-05-20 19:43:26 +02:00
udev.conf udevadm: control - use getopt_long() 2008-09-03 21:56:47 +02:00

README 

udev - userspace device management

For more information see the files in the docs/ directory.

Important Note:
  Integrating udev in the system has complex dependencies and differs from distro
  to distro. All major distros depend on udev these days and the system may not
  work without a properly installed version. The upstream udev project does not
  recommend to replace a distro's udev installation with the upstream version.

Requirements:
  - Version 2.6.22 of the Linux kernel for reliable operation of this release of
    udev. The kernel must not use the CONFIG_SYSFS_DEPRECATED* option.

  - The kernel must have sysfs, unix domain sockets and networking enabled.
    Unix domain sockets (CONFIG_UNIX) as a loadable kernel module is not
    supported.

  - The proc filesystem must be mounted on /proc/, the sysfs filesystem must
    be mounted at /sys/. No other locations are supported by udev.

  - The system must have the following group names resolvable at udev startup:
      disk, cdrom, floppy, tape, audio, video, lp, tty, dialout, kmem.
    Especially in LDAP setups, it is required, that getgrnam() is able to resolve
    these group names with only the rootfs mounted, and while no network is
    available.

Operation:
  Udev creates and removes device nodes in /dev/, based on events the kernel
  sends out on device discovery or removal.

  - Very early in the boot process, the /dev/ directory should get a 'tmpfs'
    filesystem mounted, which is populated from scratch by udev. Created nodes
    or changed permissions will not survive a reboot, which is intentional.

  - The content of /lib/udev/devices/ directory which contains the nodes,
    symlinks and directories, which are always expected to be in /dev, should
    be copied over to the tmpfs mounted /dev, to provide the required nodes
    to initialize udev and continue booting.

  - The old hotplug helper /sbin/hotplug should be disabled on bootup, before
    actions like loading kernel modules are taken, which may cause a lot of
    events.

  - The udevd daemon must be started on bootup to receive netlink uevents
    from the kernel driver core.

  - All kernel events are matched against a set of specified rules in
    /lib/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 exports a major/minor number, udev will create a
    device node with the default kernel name, or the one specified by a
    matching udev rule.

Please direct any comment/question/concern to the linux-hotplug mailing list at:
  linux-hotplug@vger.kernel.org