of the output. The number is expressed in 512-k sectors. A 100G file has
    209715200 512-k sectors. If you double this number to 200G, you get
    419430400 512-k sectors.

    d. Reload the thin pool with the new sector number, using the following
    three `dmsetup`  commands.

    ```console
    $ sudo dmsetup suspend docker-8:1-123141-pool
    $ sudo dmsetup reload docker-8:1-123141-pool --table '0 419430400 thin-pool 7:1 7:0 128 32768 1 skip_block_zeroing'
    $ sudo dmsetup resume docker-8:1-123141-pool
    ```

#### Resize a direct-lvm thin pool

To extend a `direct-lvm` thin pool, you need to first attach a new block device
to the Docker host, and make note of the name assigned to it by the kernel. In
this example, the new block device is `/dev/xvdg`.

Follow this procedure to extend a `direct-lvm` thin pool, substituting your
block device and other parameters to suit your situation.

1.  Gather information about your volume group.

    Use the `pvdisplay` command to find the physical block devices currently in
    use by your thin pool, and the volume group's name.

    ```console
    $ sudo pvdisplay |grep 'VG Name'

    PV Name               /dev/xvdf
    VG Name               docker
    ```

    In the following steps, substitute your block device or volume group name as
    appropriate.

2.  Extend the volume group, using the `vgextend` command with the `VG Name`
    from the previous step, and the name of your **new** block device.

    ```console
    $ sudo vgextend docker /dev/xvdg

    Physical volume "/dev/xvdg" successfully created.
    Volume group "docker" successfully extended
    ```

3.  Extend the `docker/thinpool` logical volume. This command uses 100% of the
    volume right away, without auto-extend. To extend the metadata thinpool
    instead, use `docker/thinpool_tmeta`.

    ```console
    $ sudo lvextend -l+100%FREE -n docker/thinpool

    Size of logical volume docker/thinpool_tdata changed from 95.00 GiB (24319 extents) to 198.00 GiB (50688 extents).
    Logical volume docker/thinpool_tdata successfully resized.
    ```

4.  Verify the new thin pool size using the `Data Space Available` field in the
    output of `docker info`. If you extended the `docker/thinpool_tmeta` logical
    volume instead, look for `Metadata Space Available`.

    ```bash
    Storage Driver: devicemapper
     Pool Name: docker-thinpool
     Pool Blocksize: 524.3 kB
     Base Device Size: 10.74 GB
     Backing Filesystem: xfs
     Data file:
     Metadata file:
     Data Space Used: 212.3 MB
     Data Space Total: 212.6 GB
     Data Space Available: 212.4 GB
     Metadata Space Used: 286.7 kB
     Metadata Space Total: 1.07 GB
     Metadata Space Available: 1.069 GB
    <...>
    ```

### Activate the `devicemapper` after reboot

If you reboot the host and find that the `docker` service failed to start,
look for the error, "Non existing device". You need to re-activate the
logical volumes with this command:

```console
$ sudo lvchange -ay docker/thinpool
```

## How the `devicemapper` storage driver works

> [!WARNING]
> Do not directly manipulate any files or directories within
> `/var/lib/docker/`. These files and directories are managed by Docker.

Use the `lsblk` command to see the devices and their pools, from the operating
system's point of view:

```console
$ sudo lsblk

NAME                    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
xvda                    202:0    0    8G  0 disk
└─xvda1                 202:1    0    8G  0 part /
xvdf                    202:80   0  100G  0 disk
├─docker-thinpool_tmeta 253:0    0 1020M  0 lvm
│ └─docker-thinpool     253:2    0   95G  0 lvm
└─docker-thinpool_tdata 253:1    0   95G  0 lvm
  └─docker-thinpool     253:2    0   95G  0 lvm
```

Use the `mount` command to see the mount-point Docker is using:

```console
$ mount |grep devicemapper
/dev/xvda1 on /var/lib/docker/devicemapper type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
```

When you use `devicemapper`, Docker stores image and layer contents in the