3 Major changes happened with this release. The goal is to take over the
4 complete kernel-event handling and provide a more efficient way to dispatch
5 kernel events. Replacing most of the current shell script logic and the
6 kernel forked helper with a netlink-daemon and a rule-based event handling.
8 o udevd listens to netlink events now. The first valid netlink event
9 will make udevd ignore any message from udevsend that contains a
10 SEQNUM, to avoid duplicate events. The forked events can be disabled
12 echo "" > /proc/sys/kernel/hotplug
13 For full support, the broken input-subsytem needs to be fixed, not to
14 bypass the driver core.
16 o /etc/dev.d/ + /etc/hotplug.d/ directory multiplexing is completely
17 removed from udev itself and must be emulated by calling small
18 helper binaries provided in the extras folder:
19 make EXTRAS=extras/run_directory/
20 will build udev_run_devd and udev_run_hotplugd, which can be called
21 from a rule if needed:
22 RUN+="/sbin/udev_run_hotplugd"
23 The recommended way to handle this is to convert all the calls from
24 the directories to explicit udev rules and get completely rid of the
25 multiplexing. (To catch a ttyUSB event, you now no longer need to
26 fork and exit 300 tty script instances you are not interested in, it
27 is just one rule that matches exactly the device.)
29 o udev handles now _all_ events not just events for class and block
30 devices, this way it is possible to control the complete event
31 behavior with udev rules. Especially useful for rules like:
32 ACTION="add", DEVPATH="/devices/*", MODALIAS=="?*", RUN+="/sbin/modprobe $modalias"
34 o As used in the modalias rule, udev supports now textual
35 substitution placeholder along with the usual format chars. This
36 needs to be documented, for now it's only visible in udev_rules_parse.c.
38 o The rule keys support now more operations. This is documented in the
39 man page. It is possible to add values to list-keys like the SYMLINK
40 and RUN list with KEY+="value" and to clear the list by assigning KEY="".
41 Also "final"-assignments are supported by using KEY:="value", which will
42 prevent changing the key by any later rule.
44 o kernel 2.6.12 has the "detached_state" attribute removed from
45 sysfs, which was used to recognize sysfs population. We switched that
46 to wait for the "bus" link, which is only available in kernels after 2.6.11.
47 Running this udev version on older kernels may cause a short delay for
50 o To provide infrastructure for persistent device naming, the id programs:
51 scsi_id, vol_id (former udev_volume_id), and ata_id (new) are able now
52 to export the probed data in environment key format:
53 pim:~ # /sbin/ata_id --export /dev/hda
54 ID_MODEL=HTS726060M9AT00
55 ID_SERIAL=MRH401M4G6UM9B
59 KERNEL="hd*[!0-9]", IMPORT="/sbin/ata_id --export $tempnode"
60 KERNEL="hd*[!0-9]", ENV{ID_SERIAL}=="?*", SYMLINK+="disk/by-id/$env{ID_MODEL}_$env{ID_SERIAL}"
63 kay@pim:~> tree /dev/disk
66 | |-- HTS726060M9AT00_MRH401M4G6UM9B -> ../../hda
67 | `-- IBM-Memory_Key -> ../../sda
69 | |-- swap -> ../../hda1
70 | |-- date -> ../../sda1
71 | `-- home -> ../../hda3
73 |-- 2E08712B0870F2E7 -> ../../hda3
74 |-- 9352cfef-7687-47bc-a2a3-34cf136f72e1 -> ../../hda1
75 |-- E845-7A89 -> ../../sda1
76 `-- b2a61681-3812-4f13-a4ff-920d70604299 -> ../../hda2
78 The IMPORT= operation will import these keys in the environment and make
79 it available for later PROGRAM= and RUN= executed programs. The keys are
80 also stored in the udevdb and can be queried from there with one of the
83 o A few binaries are silently added to the repository, which can be used
84 to replay kernel events from initramfs instead of using coldplug. udevd
85 can be instructed now to queue-up events while the stored events from
86 initramfs are filled into the udevd-queue. This code is still under
87 development and there is no documentation now besides the code itself.
88 The additional binaries get compiled, but are not installed by default.
90 o There is also a temporary fix for a performance problem where too many
91 events happen in parallel and every event needs to parse the rules.
92 udev can now read precompiled rules stored on disk. This is likely to be
93 replaced by a more elegant solution in a future udev version.
97 With kernel version 2.6.12, the sysfs file "detached_state" was removed.
98 Fix for libsysfs not to expect this file was added.
102 All rules are applied now, but only the first matching rule with a NAME-key
103 will be applied. All later rules with NAME-key are completely ignored. This
104 way system supplied symlinks or permissions gets applied to user-defined
108 Please check your rules setup, if you may need to add OPTIONS="last_rule"
109 to some rules, to keep the old behavior.
111 The rules are read on "remove"-events too. That makes is possible to match
112 with keys that are available on remove (KERNEL, SUBSYSTEM, ID, ENV, ...) to
113 instruct udev to ignore an event (OPTIONS="ignore_device").
114 The new ACTION-key may be used to let a rule act only at a "remove"-event.
116 The new RUN-key supports rule-based execution of programs after device-node
117 handling. This is meant as a general replacement for the dev.d/-directories
118 to give fine grained control over the execution of programs.
120 The %s{}-sysfs format char replacement values are searched at any of the
121 devices in the device chain now, not only at the class-device.
123 We support log priority levels now. The value udev_log in udev.conf is used
124 to determine what is printed to syslog. This makes it possible to
125 run a version with compiled-in debug messages in a production environment
126 which is sometimes needed to find a bug.
127 It is still possible to supress the inclusion of _any_ syslog usage with
128 USE_LOG=false to create the smallest possible binaries if needed.
129 The configured udev_log value can be overridden with the environment variable
134 Possible use of a system-wide klibc:
135 make USE_KLIBC=true KLCC=/usr/bin/klcc all
136 will link against an external klibc and our own version will be ignored.
140 We support an unlimited count of symlinks now.
142 If USE_STATIC=true is passed to a glibc build, we link statically and use
143 a built-in userdb parser to resolve user and group names.
145 The PLACE= key is gone. It can be replaced by an ID= for a long time, cause
146 we walk up the chain of physical devices to find a match.
148 The KEY="<value>" format supports '=', '==', '!=,' , '+=' now. This makes it
149 easy to skip certain attribute matches without composing rules with weird
150 character class negations like:
151 KERNEL="[!s][!c][!d]*"
152 this can now be replaced with:
154 The current simple '=' is still supported, and should work as it does today,
155 but existing rules should be converted if possible, to be better readable.
157 We have new ENV{}== key now, to match against a maximum of 5 environment
160 udevstart is its own binary again, cause we don't need co carry this araound
161 with every forked event.