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authorKay Sievers <kay.sievers@vrfy.org>2009-08-31 10:19:40 +0200
committerKay Sievers <kay.sievers@vrfy.org>2009-08-31 10:19:40 +0200
commita6c5b514d8e698316c57a0cf5183fcd8a7bc6d26 (patch)
treeb5c28c2a1b99d752db577ef5e8cfadd9b08dac3d /README
parent959e8b5decb32fda0a8c8be21aff8bc17382586d (diff)
update README
Diffstat (limited to 'README')
-rw-r--r--README33
1 files changed, 17 insertions, 16 deletions
diff --git a/README b/README
index 591e03a057..f6d1ab5257 100644
--- a/README
+++ b/README
@@ -8,8 +8,8 @@ recommend to replace a distro's udev installation with the upstream version.
Tools and rules shipped by udev are not public API and may change at any time.
Never call any private tool in /lib/udev from any external application, it might
just go away in the next release. Access to udev information is only offered
-by udevadm and libudev. Tools and rules in /lib/udev and the entire content of
-/dev/.udev/ is private to udev.
+by udevadm and libudev. Tools and rules in /lib/udev, and the entire content of
+the /dev/.udev directory is private to udev and does change whenever needed.
Requirements:
- Version 2.6.25 of the Linux kernel with sysfs, procfs, signalfd, inotify,
@@ -25,16 +25,16 @@ Requirements:
CONFIG_INOTIFY=y
CONFIG_SIGNALFD=y
CONFIG_TMPFS_POSIX_ACL=y (user ACLs for device nodes)
- CONFIG_BLK_DEV_BSG=y (SCSI tape devices)
+ CONFIG_BLK_DEV_BSG=y (SCSI devices)
- - For reliable operation, the kernel must not use the CONFIG_SYSFS_DEPRECATED*
+ - For reliable operations, the kernel must not use the CONFIG_SYSFS_DEPRECATED*
option.
- - Unix domain sockets (CONFIG_UNIX) as a loadable kernel module is not
- supported.
+ - Unix domain sockets (CONFIG_UNIX) as a loadable kernel module may work,
+ but it 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 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.
@@ -47,29 +47,30 @@ Requirements:
--disable-extras option.
Operation:
- Udev creates and removes device nodes in /dev/, based on events the kernel
+ Udev creates and removes device nodes in /dev, based on events the kernel
sends out on device discovery or removal.
- - Early in the boot process, the /dev/ directory should get a 'tmpfs'
+ - Early in the boot process, the /dev directory should get a 'tmpfs'
filesystem mounted, which is maintained 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,
+ - 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 in the kernel
- configuration, it is not needed, and may render the system unusable
- because of a fork-bombing behavior.
+ - The deprecated hotplug helper /sbin/hotplug should be disabled in the
+ kernel configuration, it is not needed today, and may render the system
+ unusable because the kernel may create too many processes in parallel
+ so that the system runs out-of-memory.
- 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
+ /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:
+Please direct any comment/question to the linux-hotplug mailing list at:
linux-hotplug@vger.kernel.org