Step‑by‑Step Guide to Expanding a Mounted Linux Disk with XFS

When a mounted disk (e.g., /dev/sdb mounted at /apps ) reaches high usage (over 85%), you can expand storage by adding a new disk (e.g., /dev/sdc ).

Initial disk list (output of lsblk ) shows existing disks sda , sdb , and sdc .

Environment preparation :

Create the mount point: mkdir /apps

Partition the existing disk: fdisk /dev/sdb

Format the new partition with XFS: mkfs.xfs /dev/sdb1

Verify the filesystem: blkid /dev/sdb1

Edit /etc/fstab to add an entry for automatic mounting.

Disk expansion :

Create a new mount point: mkdir /data

Partition the added disk: fdisk /dev/sdc

Format the new partition: mkfs.xfs /dev/sdc1

Verify the new filesystem: blkid /dev/sdc1

Edit /etc/fstab to mount /dev/sdc1 at /data on boot.

Copy existing data: cp -a /apps/. /data/

Compare sizes to confirm successful copy: du -sh /apps and du -sh /data

Unmount the original mount point: umount /apps

After these steps, the new disk provides additional space (e.g., 30 GB with only 1 % used) and the system continues to operate with the expanded storage.