How to Expand a CentOS Data Disk Without Partitions Using resize2fs and xfs_growfs

When a data disk has no partitions and only a filesystem (or has been formatted directly), it can be mounted and used immediately.

In this example, a CentOS 7.4 64‑bit system has a data disk /dev/sdb of 5 GB with no partitions, only a filesystem. After expanding the disk size to 10 GB in the console, the following steps demonstrate how to extend the filesystem so the additional space becomes usable.

Extending an ext* filesystem

Run the resize command: resize2fs /dev/sdb

# resize2fs /dev/sdb
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/sdb is mounted on /data; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 2
The filesystem on /dev/sdb is now 2621440 blocks long.

Verify the result: df -TH

# df -Th
Filesystem              Type      Size  Used Avail Use% Mounted on
device/tmpfs            devtmpfs  475M     0  475M   0% /dev
tmpfs                  tmpfs     487M     0  487M   0% /dev/shm
... (other mounts) ...
/dev/sdb                ext4      9.8G   23M  9.3G   1% /data

Extending an XFS filesystem

Run the XFS grow command: xfs_growfs /dev/vdb

# xfs_growfs /dev/vdb
meta-data=... (output omitted for brevity)
data blocks changed from 2621440 to 15728640.

Verify the result: df -TH

# df -TH
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/vdb       xfs        60G   34M   60G   1% /mnt/sdc

These commands allow the newly added disk space to be utilized without recreating partitions or reformatting.