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Documentation / device-mapper / dm-uevent.txt




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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:00 EST.

1	The device-mapper uevent code adds the capability to device-mapper to create
2	and send kobject uevents (uevents).  Previously device-mapper events were only
3	available through the ioctl interface.  The advantage of the uevents interface
4	is the event contains environment attributes providing increased context for
5	the event avoiding the need to query the state of the device-mapper device after
6	the event is received.
7	
8	There are two functions currently for device-mapper events.  The first function
9	listed creates the event and the second function sends the event(s).
10	
11	void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
12	                    const char *path, unsigned nr_valid_paths)
13	
14	void dm_send_uevents(struct list_head *events, struct kobject *kobj)
15	
16	
17	The variables added to the uevent environment are:
18	
19	Variable Name: DM_TARGET
20	Uevent Action(s): KOBJ_CHANGE
21	Type: string
22	Description:
23	Value: Name of device-mapper target that generated the event.
24	
25	Variable Name: DM_ACTION
26	Uevent Action(s): KOBJ_CHANGE
27	Type: string
28	Description:
29	Value: Device-mapper specific action that caused the uevent action.
30		PATH_FAILED - A path has failed.
31		PATH_REINSTATED - A path has been reinstated.
32	
33	Variable Name: DM_SEQNUM
34	Uevent Action(s): KOBJ_CHANGE
35	Type: unsigned integer
36	Description: A sequence number for this specific device-mapper device.
37	Value: Valid unsigned integer range.
38	
39	Variable Name: DM_PATH
40	Uevent Action(s): KOBJ_CHANGE
41	Type: string
42	Description: Major and minor number of the path device pertaining to this
43	event.
44	Value: Path name in the form of "Major:Minor"
45	
46	Variable Name: DM_NR_VALID_PATHS
47	Uevent Action(s): KOBJ_CHANGE
48	Type: unsigned integer
49	Description:
50	Value: Valid unsigned integer range.
51	
52	Variable Name: DM_NAME
53	Uevent Action(s): KOBJ_CHANGE
54	Type: string
55	Description: Name of the device-mapper device.
56	Value: Name
57	
58	Variable Name: DM_UUID
59	Uevent Action(s): KOBJ_CHANGE
60	Type: string
61	Description: UUID of the device-mapper device.
62	Value: UUID. (Empty string if there isn't one.)
63	
64	An example of the uevents generated as captured by udevmonitor is shown
65	below.
66	
67	1.) Path failure.
68	UEVENT[1192521009.711215] change@/block/dm-3
69	ACTION=change
70	DEVPATH=/block/dm-3
71	SUBSYSTEM=block
72	DM_TARGET=multipath
73	DM_ACTION=PATH_FAILED
74	DM_SEQNUM=1
75	DM_PATH=8:32
76	DM_NR_VALID_PATHS=0
77	DM_NAME=mpath2
78	DM_UUID=mpath-35333333000002328
79	MINOR=3
80	MAJOR=253
81	SEQNUM=1130
82	
83	2.) Path reinstate.
84	UEVENT[1192521132.989927] change@/block/dm-3
85	ACTION=change
86	DEVPATH=/block/dm-3
87	SUBSYSTEM=block
88	DM_TARGET=multipath
89	DM_ACTION=PATH_REINSTATED
90	DM_SEQNUM=2
91	DM_PATH=8:32
92	DM_NR_VALID_PATHS=1
93	DM_NAME=mpath2
94	DM_UUID=mpath-35333333000002328
95	MINOR=3
96	MAJOR=253
97	SEQNUM=1131
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