If volumes are missing on a Linux system, what is the first command to check?

The first command to check when volumes are missing in a Linux system is "pvscan." This command scans for physical volumes in the system and provides information on the status of these volumes. Physical volumes are the actual disk devices or partitions that have been initialized for use by Logical Volume Manager (LVM).

Using pvscan is a logical starting point because it helps to identify any physical volumes that may not be recognized or are missing from the LVM configuration. If there are issues with the physical volumes, this command will allow you to see if they are present and what their status is, which is crucial for diagnosing problems with missing volumes.

The other commands serve different functions within the LVM framework. For instance, lvscan is used to scan and list logical volumes, while vgscan scans for volume groups. The fdisk -l command is a lower-level disk utility that lists partitions but does not specifically target issues related to LVM. Therefore, in the context of missing volumes, starting with pvscan makes the most sense for isolating the problem at the physical volume level.