====== Problem with  LVM ======

===== A filesystem is automaticaly unmounted after 15 min ====

I got the problem, when moving an LV to a new VG (/var/log/messages)
<code>
Aug 19 16:53:44 xxxxxxx systemd: Removed slice User Slice of root.
Aug 19 16:57:03 xxxxxxx rsyslogd: -- MARK --
Aug 19 16:57:27 xxxxxxx systemd: Stopped target Local File Systems.
Aug 19 16:57:27 xxxxxxx systemd: Unmounting /ispd1/db/arclog...
Aug 19 16:57:28 xxxxxxx kernel: XFS (dm-25): Unmounting Filesystem
Aug 19 16:57:28 xxxxxxx systemd: Unmounted /ispd1/db/arclog.
Aug 19 16:57:28 xxxxxxx systemd: Stopped File System Check on /dev/mapper/vg_ispd1db-lv_ispd1arc.
Aug 19 17:00:01 xxxxxxx systemd: Created slice User Slice of root.
Aug 19 17:00:01 xxxxxxx systemd: Started Session 5395 of user root.
</code>

**solution:** systemd is not aware of the change of logical volume/volume group\\
Reload the systemd daemon
<cli prompt='#'>
[root@xxxxxxx] ~ # systemctl daemon-reload
[root@xxxxxxx] ~ # systemctl status ispd1-db-arclog.mount
● ispnprd1-db-arclog.mount - /ispd1/db/arclog
   Loaded: loaded (/etc/fstab; bad; vendor preset: disabled)
   Active: active (mounted) since Wed 2020-08-19 17:33:21 CEST; 19h ago
    Where: /ispd1/db/arclog
     What: /dev/mapper/vg_ispd1arc-lv_ispd1arc
     Docs: man:fstab(5)
           man:systemd-fstab-generator(8)
[root@xxxxxxx]) ~ # systemctl show ispd1-db-arclog.mount
Where=/ispd1/db/arclog
What=/dev/mapper/vg_ispd1arc-lv_ispd1arc
...
</cli>

you can also check using
  systemctl show dev-mapper-vg_ispd1arc.lv_ispd1arc.device
  systemctl show dev-mapper-vg_ispd1arc
  
===== Recovering Physical Volume Metadata =====

Symptom:
<cli prompt='#'>
[root@lnx001] ~ # pvs
  PV         VG      Fmt  Attr PSize    PFree
  /dev/sda2  vg_root lvm2 a--   <49.51g <25.26g
  [unknown]  vg_root lvm2 a--   <49.51g <25.26g
</cli>

The VG is not active

You should not attempt this procedure with a working LVM logical volume. You will lose your data if you specify the incorrect UUID.

<cli prompt='#'>
[root@lnx001] ~ # vgchange -an --partial
Partial mode. Incomplete volume groups will be activated read-only.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
</cli>

Restore the PVID on disk partition 
<cli prompt='#'>
[root@lnx001] ~ # pvcreate --uuid "FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk" --restorefile /etc/lvm/archive/vg_root_00050.vg /dev/sda3
  Physical volume "/dev/sda3" successfully created
</cli>  

Restore the VG
<cli prompt='#'>
[root@lnx001] ~ # vgcfgrestore vg_root
  Restored volume group vg_root
</cli>

List the LVs
<cli prompt='#'>
[root@lnx001] ~ # lvs -a -o +devices
  LV              VG      Attr       LSize    Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices
  lv_home         vg_root -wi-------    2.00g                                                     /dev/sda2(3712)
  lv_opt          vg_root -wi-------  512.00m                                                     /dev/sda3(1536)
  lv_opt_tivoli   vg_root -wi-------    2.00g                                                     /dev/sda3(1024)
</cli>

Activate the LVs
<cli prompt='#'>
[root@lnx001] ~ # lvchange -ay /dev/vg_root/lv_home 
[root@lnx001] ~ # lvs -a -o +devices
  LV              VG      Attr       LSize    Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices
  lv_home         vg_root -wi-a-----    2.00g                                                     /dev/sda2(3712)
  lv_opt          vg_root -wi-------  512.00m                                                     /dev/sda3(1536)
  lv_opt_tivoli   vg_root -wi-------    2.00g                                                     /dev/sda3(1024)
</cli>

===== Recovering Volume Group Metadata =====

Restore VG metadata
<cli prompt='#'>
# vgcfgrestore VG
  Restored volume group VG
</cli>

Assign a random UUID to VG
<cli prompt='#'>
# vgchange -an vg-name
# vgchange --uuid <vg-name>
# vgchange -an vg-name
</cli>