How to Shrink /home and Expand the Root Partition on CentOS 7

Phenomenon

The log server was originally set up with an unreasonable partition layout, leaving the /home directory oversized.

Goal

Reduce the size of the /home partition and extend the root (/) partition to use the freed space.

Step 1 – Identify why /home cannot be unmounted

Attempting umount /home returns “target busy”. The usual way to find the holding process is fuser -m /home, but the fuser command is missing.

# umount /home
umount: /home: target busy.

Step 2 – Install the missing utility

On CentOS 7 the fuser command is provided by the psmisc package.

# yum install psmisc

Step 3 – Locate and kill the offending process

Run fuser -m /home to list PIDs, then terminate them.

# fuser -m /home   // shows PIDs using /home
# kill -9 11757    // stop the process

After the processes are stopped, unmount the filesystem.

# umount /home

Step 4 – Verify the filesystem type

Check /etc/fstab to confirm that /home uses XFS.

# cat /etc/fstab | grep centos-home

Step 5 – Install XFS tools (if needed)

Resizing an XFS filesystem requires the xfsdump utility.

# yum install xfsdump -y

Step 6 – Shrink the /home partition

Resize the logical volume and filesystem to the desired size (e.g., 100 GB).

# resize2fs -p /dev/mapper/centos-home 100G

Step 7 – Expand the root partition

After freeing space from /home, extend the root logical volume and resize its filesystem accordingly (commands omitted for brevity).

Step 8 – Remount /home

Attempt to mount the resized /home. If the superblock cannot be read, the partition must be reformatted, so back up all data before proceeding.

# mount /home
mount: /dev/mapper/centos-home: cannot read superblock

Backup /home, format if necessary, then mount again.

Important Note

Always back up the contents of /home before shrinking or reformatting the partition.