vgmknodes

vgmknodes [VolumeGroupName]

VolumeGroupName
    Specifies the name of the Volume Group for which to create device nodes. If no Volume Group is specified, it creates device nodes for all active Volume Groups.

The `vgmknodes` command is a utility for creating device nodes in `/dev` for Logical Volumes (LVs) and Volume Groups (VGs). It ensures that the necessary device nodes exist so that LVM (Logical Volume Manager) can properly access the logical volumes. Device nodes are special files that provide an interface to hardware devices. When LVM creates or activates a volume group or logical volume, it relies on these device nodes to interact with the underlying physical volumes. If the device nodes are missing or incorrect, LVM operations might fail. `vgmknodes` automatically generates the necessary device nodes by scanning the active volume groups. It is often run automatically during system startup or when new physical volumes are added. It can also be run manually to resolve issues with missing or incorrect device nodes, but usually this process is handled automatically.
This command is especially useful in environments with complex device naming schemes or when the device nodes have been inadvertently removed or corrupted.
Using `vgmknodes` ensures that the logical volumes can be accessed by the system.

It's usually not necessary to run this command manually unless there are issues with device node creation. Incorrect use might lead to inconsistencies if run at the wrong time or on the incorrect volume groups. Also, direct modification of `/dev/mapper` nodes is strongly discouraged; use LVM tools to manage them.

A typical usage scenario is during system startup where the LVM initialization scripts call `vgmknodes` to ensure all logical volumes are accessible. It is also used after adding new physical volumes or after encountering errors related to device node access.

The `vgmknodes` command basically scans the active volume groups, determines the necessary device nodes and uses `mknod(1)` to create nodes if they don't exist.

The `vgmknodes` command is part of the LVM2 suite, which is a more advanced and flexible successor to the original LVM. Its introduction was necessary to handle the complexities of modern storage systems and to provide a more robust mechanism for managing logical volumes. The command evolved alongside LVM, adapting to changes in kernel device management and storage technologies. Early versions aimed at ensuring device node integrity and accessibility. The command saw heavy usage when LVM was still a new paradigm.

lvm(8), vgcreate(8), lvcreate(8), pvcreate(8), mknod(1)