How to Expand an Unpartitioned Data Disk on CentOS 7.4 Without Reboot

The article uses a CentOS 7.4 64‑bit example where the data disk /dev/sdb originally has 5 GB, no partitions, and only a filesystem. After expanding the disk to 10 GB in the cloud console, the guide shows how to make the additional space usable.

Ext* filesystem expansion

Run the resize2fs command on the device to grow the filesystem.

# 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 new size with df -TH .

# df -Th
Filesystem              Type      Size  Used Avail Use% Mounted on
/dev/mapper/centos-root xfs        17G  1.7G   16G  10% /
/dev/sda1               xfs      1014M  138M  877M  14% /boot
/dev/sdb                ext4      9.8G   23M  9.3G   1% /data

XFS filesystem expansion

Run xfs_growfs on the XFS device.

# xfs_growfs /dev/vdb
meta-data=data=/dev/vdb isize=512 agcount=4, agsize=655360 blks
... (truncated output) ...
data blocks changed from 2621440 to 15728640.

Check the expanded size with df -TH .

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

Before and after the operations, lsblk can be used to view the disk layout and confirm that the device now shows the increased size (e.g., sdb 10G instead of 5G).