lv extend | lvextend new size matches existing

Logical Volume Management (LVM) is a powerful tool in Linux for managing storage. It allows for flexible partitioning and resizing of storage volumes, making it ideal for dynamic environments where storage needs can change rapidly. One of the core operations in LVM is extending the size of a Logical Volume (LV), which is where the `lvextend` command comes into play. This article provides a comprehensive guide on using `lvextend` to increase the size of your LVs without requiring a system reboot, covering various options, examples, and best practices. We'll also delve into comparisons with related commands like `lvresize`, explore specific scenarios like extending to 100% of available space, and address common issues like mismatched sizes.

Understanding the Basics: LVM and Logical Volumes

Before diving into `lvextend`, let's briefly recap the fundamental concepts of LVM:

* Physical Volumes (PVs): These are the underlying physical storage devices (e.g., hard drives, SSDs, partitions) that form the foundation of LVM.

* Volume Groups (VGs): A VG is a container that groups together one or more PVs. It provides a unified pool of storage from which LVs can be carved out.

* Logical Volumes (LVs): LVs are the virtual partitions that you create within a VG. They are the logical representation of storage that the operating system actually uses. They are analogous to traditional partitions but offer much greater flexibility.

The beauty of LVM lies in its abstraction. You don't directly manage physical partitions; instead, you work with logical volumes, which can be resized, moved, and managed much more easily.

Introducing the `lvextend` Command

The `lvextend` command is specifically designed to increase the size of an existing LV. It works by allocating space from the VG to the LV. The key advantage of `lvextend` is that it can typically be performed online, meaning you don't need to unmount the LV or reboot the system, minimizing downtime.

Syntax of `lvextend`

The general syntax of the `lvextend` command is:

```bash

lvextend [options]

Let's break down the components:

* `lvextend`: The command itself.

* `[options]`: Various options to modify the command's behavior (discussed in detail below).

* ``: The amount of space you want to add to the LV. This can be specified in various units like kilobytes (k), megabytes (m), gigabytes (g), terabytes (t), or as a percentage of the VG's free space.lv extend

* ``: The path to the LV you want to extend. This is typically in the format `/dev/mapper/-` or `/dev//`.

Essential `lvextend` Options

Here's a rundown of the most commonly used options with `lvextend`:

* `-L, --size `: Specifies the new size of the LV. If you use this option, `lvextend` will resize the LV to the *exact* size you specify. Remember to include the unit (e.g., `-L 20G`).

* `+`: Specifies the amount of space to *add* to the LV. This is the more common and generally safer approach. The '+' sign indicates that the size is to be added to the existing LV size.

* `-l, --extents [%{VG|FREE|PVS}]`: Specifies the number of logical extents to add to the LV. Logical extents are the smallest units of storage allocation in LVM. This option is less commonly used directly, but it can be helpful in specific situations.

* `%VG`: Percentage of the total VG size.

* `%FREE`: Percentage of the free space in the VG.

* `%PVS`: Percentage of the size of the PVs in the VG.

* `-r, --resizefs`: Automatically resize the file system after extending the LV. This is a crucial option and highly recommended, as simply extending the LV doesn't automatically expand the file system to fill the new space. If omitted, you'll need to resize the file system manually (see `resize2fs` below).

* `-n, --nofsresize`: Prevents the file system from being resized automatically, even if `-r` is specified. This is useful if you want to postpone the file system resize for later, perhaps during a maintenance window.

* `-v, --verbose`: Enables verbose output, providing more detailed information about the extension process. Helpful for troubleshooting.

* `-t, --test`: Performs a dry run. Shows what *would* happen without actually making any changes. Essential for testing your command before execution.

* `-i, --stripes `: Specifies the number of stripes for the LV. This is more relevant when creating LVs but can be used when extending to influence performance.

* `-I, --stripesize `: Specifies the stripe size. Works in conjunction with `-i`.