问题

LVM 命令显示以下错误：

# pvs
WARNING: Failed to connect to lvmetad. Falling back to device scanning.    <<<
警告：无法连接到 lvmetad。 回退到设备扫描。

PV VG Fmt Attr PSize PFree
/dev/sd[X][partition_number] [vg_name] lvm2 a-- [size]g [available_free_space]g

# vgs
WARNING: Failed to connect to lvmetad. Falling back to device scanning.    <<<
VG #PV #LV #SN Attr VSize VFree
[vg_name] [number_of_pvs]  [number of lvs] 0 wz--n- [size]g [available_free_space]g

# lvs
WARNING: Failed to connect to lvmetad. Falling back to device scanning.    <<<
LV VG Attr LSize Pool Oroirn Data% Meta% Move Log Cpy%Sync Convert
[lv_name] [vg_name] -wi-ao---- [size]g

/var/log/messages 文件中的错误：

# grep lvmetad /var/log/messages
Sep 8 20:34:29 [hostname] systemd: Cannot add dependency job for unit lvm2-lvmetad.socket, ignoring: Unit is masked.
Sep 8 20:34:31 [hostname]t lvm: pvscan[642] activating all directly (lvmetad unused) 8:17
Sep 8 20:34:31 [hostname] lvm: WARNING: Autoactivation reading from disk instead of lvmetad.
Sep 8 20:34:31 [hostname] lvm: WARNING: Failed to connect to lvmetad. Falling back to device scanning.
lvm：警告：从磁盘而不是 lvmetad 读取自动激活。
lvm：警告：无法连接到 lvmetad。 回退到设备扫描。

解决方案

lvm2-lvmetad.service 和 lvm2-lvmetad.socket 服务在没有遵循正确步骤的情况下被禁用。
/etc/lvm/lvm.conf 配置为使用 use_lvmetad，其中 lvm2-lvmetad.service 和 lvm2-lvmetad.socket 服务被屏蔽。

# grep "use_lvmetad =" /etc/lvm/lvm.conf
use_lvmetad = 1

# systemctl status lvm2-lvmetad.service
● lvm2-lvmetad.service
Loaded: masked (/dev/null; bad)      >>>>> Masked      
Active: inactive (dead)
Warning: lvm2-lvmetad.service changed on disk. Run 'systemctl daemon-reload' to reload units.

# systemctl status lvm2-lvmetad.socket
● lvm2-lvmetad.socket
Loaded: masked (/dev/null; bad)      >>>>> Masked
Active: inactive (dead)
Sep 08 20:34:32  systemd[1]: Cannot add dependency job for unit lvm2-lvmetad.socket, ignoring: Invalid request descriptor
Sep 08 20:34:38  systemd[1]: Cannot add dependency job for unit lvm2-lvmetad.socket, ignoring: Unit is masked.
Warning: lvm2-lvmetad.socket changed on disk. Run 'systemctl daemon-reload' to reload units.

首先取消屏蔽 lvm2-lvmetad.socket 和 lvm2-lvmetad.service。
然后使用以下命令在启动时启动并启用服务。

# systemctl unmask lvm2-lvmetad.service lvm2-lvmetad.socket
# systemctl start lvm2-lvmetad.service lvm2-lvmetad.socket
# systemctl enable lvm2-lvmetad.service lvm2-lvmetad.socket

如果需要禁用 lvm2-lvmetad.socket 和 lvm2-lvmetad.service，则需要将 /etc/lvm/lvm.conf 配置为不使用“use_lvmetad”。
（即 use_lvmetad = 0）