根据这篇文章，一直在尝试在 Fedora 20 主机上挂载 qcow2 类型的 QEMU 映像http://docs.openstack.org/image-guide/content/ch_modifying_images.html 看来“vgscan”在 /dev/nbd0 上看不到我链接到我的图像的分区：
% vgscan -vvv
Setting activation/monitoring to 1
Processing: vgscan -vvv
O_DIRECT will be used
Setting global/locking_type to 1
Setting global/wait_for_locks to 1
File-based locking selected.
Setting global/locking_dir to /run/lock/lvm
Setting global/prioritise_write_locks to 1
Locking /run/lock/lvm/P_global WB
_do_flock /run/lock/lvm/P_global:aux WB
_do_flock /run/lock/lvm/P_global WB
_undo_flock /run/lock/lvm/P_global:aux
Metadata cache has no info for vgname: "#global"
Wiping cache of LVM-capable devices
/dev/sda: Added to device cache
/dev/disk/by-id/ata-WDC_WD10EZEX-75M2NA0_WD-WCC3F4935054: Aliased to /dev/sda in device cache
/dev/disk/by-id/wwn-0x50014ee25f867e03: Aliased to /dev/sda in device cache
/dev/sda1: Added to device cache
/dev/disk/by-id/ata-WDC_WD10EZEX-75M2NA0_WD-WCC3F4935054-part1: Aliased to /dev/sda1 in device cache
/dev/disk/by-id/wwn-0x50014ee25f867e03-part1: Aliased to /dev/sda1 in device cache
/dev/disk/by-uuid/1c1a9d75-070a-4c5b-8d66-24cae1141dd7: Aliased to /dev/sda1 in device cache
/dev/sda2: Added to device cache
/dev/disk/by-id/ata-WDC_WD10EZEX-75M2NA0_WD-WCC3F4935054-part2: Aliased to /dev/sda2 in device cache
/dev/disk/by-id/lvm-pv-uuid-DnkMt8-bu1E-7dJo-Sdcc-GlT6-sKec-FjFj1o: Aliased to /dev/sda2 in device cache
/dev/disk/by-id/wwn-0x50014ee25f867e03-part2: Aliased to /dev/sda2 in device cache
/dev/sr0: Added to device cache
/dev/cdrom: Aliased to /dev/sr0 in device cache (preferred name)
/dev/disk/by-id/ata-ASUS_DRW-24F1ST_a_S10K68EF300J0B: Aliased to /dev/cdrom in device cache
/dev/nbd0: Added to device cache
/dev/nbd0p1: Added to device cache
/dev/nbd0p2: Added to device cache
/dev/nbd1: Added to device cache
/dev/nbd10: Added to device cache
/dev/nbd11: Added to device cache
/dev/nbd12: Added to device cache
/dev/nbd13: Added to device cache
/dev/nbd14: Added to device cache
/dev/nbd15: Added to device cache
/dev/nbd2: Added to device cache
/dev/nbd3: Added to device cache
/dev/nbd4: Added to device cache
/dev/nbd5: Added to device cache
/dev/nbd6: Added to device cache
/dev/nbd7: Added to device cache
/dev/nbd8: Added to device cache
/dev/nbd9: Added to device cache
/dev/dm-0: Added to device cache
/dev/disk/by-id/dm-name-fedora_nfv--s1-swap: Aliased to /dev/dm-0 in device cache (preferred name)
/dev/disk/by-id/dm-uuid-LVM-KisoyqxG0iu1uFiZsLL7nVSSX0Ow8qwTYdLBLM9aOVskeq2PlKwTefSpNK2tdqi2: Aliased to /dev/disk/by-id/dm-name-fedora_nfv--s1-swap in device cache
/dev/disk/by-uuid/fd91acd1-1ff8-4db9-a070-f999a387489c: Aliased to /dev/disk/by-id/dm-name-fedora_nfv--s1-swap in device cache
/dev/fedora_nfv-s1/swap: Aliased to /dev/disk/by-id/dm-name-fedora_nfv--s1-swap in device cache (preferred name)
/dev/mapper/fedora_nfv--s1-swap: Aliased to /dev/fedora_nfv-s1/swap in device cache
/dev/dm-1: Added to device cache
/dev/disk/by-id/dm-name-fedora_nfv--s1-root: Aliased to /dev/dm-1 in device cache (preferred name)
/dev/disk/by-id/dm-uuid-LVM-KisoyqxG0iu1uFiZsLL7nVSSX0Ow8qwTQy5rPQnLskMuc0luyn5HeUAJcC4sHz0t: Aliased to /dev/disk/by-id/dm-name-fedora_nfv--s1-root in device cache
/dev/disk/by-uuid/44fd9e97-274d-4536-b8f2-9a0d6e33a33a: Aliased to /dev/disk/by-id/dm-name-fedora_nfv--s1-root in device cache
/dev/fedora_nfv-s1/root: Aliased to /dev/disk/by-id/dm-name-fedora_nfv--s1-root in device cache (preferred name)
/dev/mapper/fedora_nfv--s1-root: Aliased to /dev/fedora_nfv-s1/root in device cache
/dev/dm-2: Added to device cache
/dev/disk/by-id/dm-name-fedora_nfv--s1-home: Aliased to /dev/dm-2 in device cache (preferred name)
/dev/disk/by-id/dm-uuid-LVM-KisoyqxG0iu1uFiZsLL7nVSSX0Ow8qwTtNmpzJ9SfcvKnnvdlfdseL6QLUnvP5vA: Aliased to /dev/disk/by-id/dm-name-fedora_nfv--s1-home in device cache
/dev/disk/by-uuid/c6b30418-b427-430d-916b-dceb4d08b5d9: Aliased to /dev/disk/by-id/dm-name-fedora_nfv--s1-home in device cache
/dev/fedora_nfv-s1/home: Aliased to /dev/disk/by-id/dm-name-fedora_nfv--s1-home in device cache (preferred name)
/dev/mapper/fedora_nfv--s1-home: Aliased to /dev/fedora_nfv-s1/home in device cache
Wiping internal VG cache
Metadata cache has no info for vgname: "#global"
Metadata cache has no info for vgname: "#orphans_lvm1"
Metadata cache has no info for vgname: "#orphans_lvm1"
lvmcache: initialised VG #orphans_lvm1
Metadata cache has no info for vgname: "#orphans_pool"
Metadata cache has no info for vgname: "#orphans_pool"
lvmcache: initialised VG #orphans_pool
Metadata cache has no info for vgname: "#orphans_lvm2"
Metadata cache has no info for vgname: "#orphans_lvm2"
lvmcache: initialised VG #orphans_lvm2
Reading all physical volumes. This may take a while...
Finding all volume groups
Asking lvmetad for complete list of known VGs
Setting response to OK
Setting response to OK
Asking lvmetad for VG Kisoyq-xG0i-u1uF-iZsL-L7nV-SSX0-Ow8qwT (name unknown)
Setting response to OK
Setting response to OK
Setting name to fedora_nfv-s1
Setting metadata/format to lvm2
Metadata cache has no info for vgname: "fedora_nfv-s1"
Setting id to DnkMt8-bu1E-7dJo-Sdcc-GlT6-sKec-FjFj1o
Setting format to lvm2
Setting device to 2050
Setting dev_size to 1952497664
Setting label_sector to 1
/dev/sda2: Device is a partition, using primary device /dev/sda for mpath component detection
Opened /dev/sda2 RO O_DIRECT
/dev/sda2: size is 1952497664 sectors
Closed /dev/sda2
/dev/sda2: size is 1952497664 sectors
Opened /dev/sda2 RO O_DIRECT
/dev/sda2: block size is 4096 bytes
/dev/sda2: physical block size is 4096 bytes
Closed /dev/sda2
lvmcache: /dev/sda2: now in VG #orphans_lvm2 (#orphans_lvm2) with 0 mdas
Setting size to 1044480
Setting start to 4096
Setting ignore to 0
Allocated VG fedora_nfv-s1 at 0x7f985779d4c0.
Metadata cache has no info for vgname: "fedora_nfv-s1"
Metadata cache has no info for vgname: "fedora_nfv-s1"
lvmcache: /dev/sda2: now in VG fedora_nfv-s1 with 1 mdas
lvmcache: /dev/sda2: setting fedora_nfv-s1 VGID to KisoyqxG0iu1uFiZsLL7nVSSX0Ow8qwT
Freeing VG fedora_nfv-s1 at 0x7f985779d4c0.
Finding volume group "fedora_nfv-s1"
Locking /run/lock/lvm/V_fedora_nfv-s1 RB
_do_flock /run/lock/lvm/V_fedora_nfv-s1:aux WB
_undo_flock /run/lock/lvm/V_fedora_nfv-s1:aux
_do_flock /run/lock/lvm/V_fedora_nfv-s1 RB
Asking lvmetad for VG Kisoyq-xG0i-u1uF-iZsL-L7nV-SSX0-Ow8qwT (fedora_nfv-s1)
Setting response to OK
Setting response to OK
Setting name to fedora_nfv-s1
Setting metadata/format to lvm2
Setting id to DnkMt8-bu1E-7dJo-Sdcc-GlT6-sKec-FjFj1o
Setting format to lvm2
Setting device to 2050
Setting dev_size to 1952497664
Setting label_sector to 1
Setting size to 1044480
Setting start to 4096
Setting ignore to 0
Allocated VG fedora_nfv-s1 at 0x7f98577920b0.
/dev/sda2 0: 0 2020: swap(0:0)
/dev/sda2 1: 2020 223521: home(0:0)
/dev/sda2 2: 225541 12800: root(0:0)
Allocated VG fedora_nfv-s1 at 0x7f98577960c0.
Found volume group "fedora_nfv-s1" using metadata type lvm2
Freeing VG fedora_nfv-s1 at 0x7f985779e0e0.
Unlock: Memlock counters: locked:0 critical:0 daemon:0 suspended:0
Syncing device names
Unlocking /run/lock/lvm/V_fedora_nfv-s1
_undo_flock /run/lock/lvm/V_fedora_nfv-s1
Freeing VG fedora_nfv-s1 at 0x7f98577960c0.
Freeing VG fedora_nfv-s1 at 0x7f98577920b0.
Unlocking /run/lock/lvm/P_global
_undo_flock /run/lock/lvm/P_global
Metadata cache has no info for vgname: "#global"
Completed: vgscan -vvv
%
vgscan 是软件包 lvm2-2.02.106-1.fc20.x86_64 的一部分
我想知道可能是什么原因，我还应该尝试什么？谢谢。
答案1
看来 lvm2 软件包中确实存在问题，因此 pvscan 无法从 nbd 设备的 udev 运行。因此，作为一种解决方案/解决方法，应在运行 vgscan 之前禁用进程 lvmetad（通过 Fedora 上的 systemctl 以及在 /etc/lvm/lvm.conf 中设置 use_lvmetad=0）。
之后 vgscan 将在 /dev/nbd* 上找到 LVM 并且可以安装它们。