1LVMAUTOACTIVATION(7) LVMAUTOACTIVATION(7)
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6 lvmautoactivation — LVM autoactivation
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9 Autoactivation is the activation of LVs performed automatically by the
10 system in response to LVM devices being attached to the machine. When
11 all PVs in a VG have been attached, the VG is complete, and LVs in the
12 VG are activated.
13 Autoactivation of VGs, or specific LVs, can be prevented using vgchange
15 or lvchange --setautoactivation n. The lvm.conf auto_activation_vol‐
16 ume_list is another way to limit autoactivation.
17 event autoactivation
19 LVM autoactivation is "event based", in which complete VGs are acti‐
20 vated in response to uevents which occur during system startup or at
21 any time after the system has started. An old form of autoactivation
22 was "static" in which complete VGs are activated at a fixed point dur‐
23 ing system startup by a systemd service, and not in response to events.
24 Event based autoactivation is driven by udev, udev rules, and systemd.
26 When a device is attached to a machine, a uevent is generated by the
27 kernel to notify userspace of the new device. systemd-udev runs udev
28 rules to process the new device. Udev rules use blkid to identify the
29 device as an LVM PV and then execute the lvm-specific udev rule for the
30 device, which triggers autoactivation.
31 There are two variations of event based autoactivation that may be used
33 on a system, depending on the LVM udev rule that is installed (found in
34 /lib/udev/rules.d/.) The following summarizes the steps in each rule
35 which lead to autoactivation:
36 69-dm-lvm-metad.rules
38 • device /dev/name with major:minor X:Y is attached to the machine
40 • systemd/udev runs blkid to identify /dev/name as an LVM PV
42 • udev rule 69-dm-lvm-metad.rules is run for /dev/name
44 • the lvm udev rule runs the systemd service lvm2-pvscan@X:Yservice
46 • the lvm2-pvscan service runs:
48 pvscan --cache -aay --major X --minor Y
49 • pvscan reads the device, records that the PV is online (see pvs_on‐
51 line), and checks if the VG is complete.
52 • if the VG is complete, pvscan creates the vgs_online temp file, and
54 activates the VG.
55 • the activation command output can be seen from systemctl status
57 lvm2-pvscan*
58 69-dm-lvm.rules
60 • device /dev/name with major:minor X:Y is attached to the machine
62 • systemd/udev runs blkid to identify /dev/name as an LVM PV
64 • udev rule 69-dm-lvm.rules is run for /dev/name
66 • the lvm udev rule runs:
68 pvscan --cache --listvg --checkcomplete --vgonline
69 --autoactivation event --udevoutput --journal=output /dev/name
70 • pvscan reads the device, records that the PV is online (see pvs_on‐
72 line), and checks if the VG is complete.
73 • if the VG is complete, pvscan creates the vgs_online temp file, and
75 prints the name of the VG for the udev rule to import:
76 LVM_VG_NAME_COMPLETE='vgname'
77 • if the lvm udev rule sees LVM_VG_NAME_COMPLETE from pvscan, it acti‐
79 vates the VG using a transient systemd service named lvm-acti‐
80 vate-<vgname>.
81 • the lvm-activate-<vgname> service runs
83 vgchange -aay --autoactivation event <vgname>
84 • the activation command output can be seen from journalctl -u lvm-ac‐
86 tivate-<vgname>
87 pvscan options
89 --cache
90 Read the <device> arg (and only that device), and record that the PV is
91 online by creating the /run/lvm/pvs_online/<pvid> file containing the
92 name of the VG and the device for the PV.
93 -aay
95 Activate the VG from the pvscan command (includes implicit --checkcom‐
96 plete and --vgonline.)
97 --checkcomplete
99 Check if the VG is complete, i.e. all PVs are present on the system, by
100 checking /run/lvm/pvs_online/<pvid> files.
101 --vgonline
103 Create /run/lvm/vgs_online/<vgname> if the VG is complete (used to en‐
104 sure only one command performs activation.)
105 --autoactivation event
107 Inform the command it is used for event based autoactivation.
108 --listvg
110 Print the name of the VG using the device.
111 --udevoutput
113 Only print output that can be imported to the udev rule, using the udev
114 environment key format, i.e. NAME='value'.
115 --journal=output
117 Send standard command output to the journal (when stdout is reserved
118 for udev output.)
119 run files
121 Autoactivation commands use a number of temp files in /run/lvm (with
122 the expectation that /run is cleared between boots.)
123 pvs_online
125 pvscan --cache creates a file here for each PV that is attached. The
126 file is named with the PVID and contains the VG name and device infor‐
127 mation. The existence of the file is used to determine when all PVs
128 for a given VG are present. The device information in these files is
129 also used to optimize locating devices for a VG when the VG is acti‐
130 vated.
131 pvs_lookup
133 pvscan --cache creates a file here named for a VG (if one doesn't al‐
134 ready exist.) The file contains a list of PVIDs in the VG. This is
135 needed when a PV is processed which has no VG metadata, in which case
136 the list of PVIDs from the lookup file is used to check if the VG is
137 complete.
138 vgs_online
140 The first activation command (pvscan or vgchange) to create a file
141 here, named for the VG, will activate the VG. This resolves a race
142 when concurrent commands attempt to activate a VG at once.
143 static autoactivation
145 A static autoactivation method is no longer provided by lvm. Setting
146 event_activation=0 still disables event based autoactivation. WARNING:
147 disabling event activation without an alternative may prevent a system
148 from booting. A custom systemd service could be written to run autoac‐
149 tivation during system startup, in which case disabling event autoacti‐
150 vation may be useful.
151
153 VG "vg" contains two PVs:
154 $ pvs -o name,vgname,uuid /dev/sdb /dev/sdc
155 PV VG PV UUID
156 /dev/sdb vg 1uKpaT-lFOZ-NLHX-j4jI-OBi1-QpdE-HZ5hZY
157 /dev/sdc vg 5J3tM8-aIPe-2vbd-DBe7-bvRq-TGj0-DaKV2G
158 use of --cache:
160 $ pvscan --cache /dev/sdb
161 pvscan[12922] PV /dev/sdb online.
162 $ pvscan --cache /dev/sdc
163 pvscan[12923] PV /dev/sdc online.
164 $ cat /run/lvm/pvs_online/1uKpaTlFOZNLHXj4jIOBi1QpdEHZ5hZY
166 8:16
167 vg:vg
168 dev:/dev/sdb
169 $ cat /run/lvm/pvs_online/5J3tM8aIPe2vbdDBe7bvRqTGj0DaKV2G
170 8:32
171 vg:vg
172 dev:/dev/sdc
173 use of -aay:
175 $ pvscan --cache -aay /dev/sdb
176 pvscan[12935] PV /dev/sdb online, VG vg incomplete (need 1).
177 $ pvscan --cache -aay /dev/sdc
178 pvscan[12936] PV /dev/sdc online, VG vg is complete.
179 pvscan[12936] VG vg run autoactivation.
180 1 logical volume(s) in volume group "vg" now active
181 $ cat /run/lvm/pvs_online/1uKpaTlFOZNLHXj4jIOBi1QpdEHZ5hZY
183 8:16
184 vg:vg
185 dev:/dev/sdb
186 $ cat /run/lvm/pvs_online/5J3tM8aIPe2vbdDBe7bvRqTGj0DaKV2G
187 8:32
188 vg:vg
189 dev:/dev/sdc
190 $ ls /run/lvm/vgs_online/vg
191 /run/lvm/vgs_online/vg
192 use of --listvg:
194 $ pvscan --cache --listvg /dev/sdb
195 VG vg
196 $ pvscan --cache --listvg /dev/sdc
197 VG vg
198 $ cat /run/lvm/pvs_online/1uKpaTlFOZNLHXj4jIOBi1QpdEHZ5hZY
200 8:16
201 vg:vg
202 dev:/dev/sdb
203 $ cat /run/lvm/pvs_online/5J3tM8aIPe2vbdDBe7bvRqTGj0DaKV2G
204 8:32
205 vg:vg
206 dev:/dev/sdc
207 use of --checkcomplete:
209 $ pvscan --cache --listvg --checkcomplete --vgonline /dev/sdb
210 pvscan[12996] PV /dev/sdb online, VG vg incomplete (need 1).
211 VG vg incomplete
212 $ pvscan --cache --listvg --checkcomplete --vgonline /dev/sdc
213 pvscan[12997] PV /dev/sdc online, VG vg is complete.
214 VG vg complete
215 use of --udevoutput:
217 $ pvscan --cache --listvg --checkcomplete --vgonline --udevoutput /dev/sdb
218 LVM_VG_NAME_INCOMPLETE='vg'
219 $ pvscan --cache --listvg --checkcomplete --vgonline --udevoutput /dev/sdc
220 LVM_VG_NAME_COMPLETE='vg'
221 use of --listlvs:
223 $ lvs -o name,devices vg
224 LV Devices
225 lvol0 /dev/sdb(0)
226 lvol1 /dev/sdc(0)
227 lvol2 /dev/sdb(1),/dev/sdc(1)
228 $ pvscan --cache --listlvs --checkcomplete /dev/sdb
230 pvscan[13288] PV /dev/sdb online, VG vg incomplete (need 1).
231 VG vg incomplete
232 LV vg/lvol0 complete
233 LV vg/lvol2 incomplete
234 $ pvscan --cache --listlvs --checkcomplete /dev/sdc
235 pvscan[13289] PV /dev/sdc online, VG vg is complete.
236 VG vg complete
237 LV vg/lvol1 complete
238 LV vg/lvol2 complete
239Red Hat, Inc LVM TOOLS 2.03.18(2)-git (2022-11-10)LVMAUTOACTIVATION(7)