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

Background

The original log server was set up with an improperly sized partition layout, leaving the /home filesystem consuming excessive space while the root partition ( /) lacked room for growth.

Goal

Reduce the /home partition to about 100 GB.

Expand the root filesystem to use the freed space.

Unmount /home safely, handling the "target busy" error.

Step 1 – Identify and Stop Processes Using /home

Attempting to unmount /home yields:

# umount /home
umount: /home：目标忙。

Use fuser (or lsof) to locate the processes. On a minimal CentOS 7 installation the fuser command may be missing, so install it first: # yum install psmisc -y After installation, run: # fuser -m /home Kill the listed processes (example PID 11757): # kill -9 11757 Now the filesystem can be unmounted:

# umount /home

Step 2 – Resize the /home Filesystem

Assuming /home is an ext4 logical volume, shrink it with: # resize2fs -p /dev/mapper/centos-home 100G Verify the filesystem type; if it is XFS, the approach differs (XFS cannot be shrunk directly). Check the /etc/fstab entry:

# cat /etc/fstab | grep centos-home

Step 3 – Prepare for XFS Expansion (if applicable)

If the partition uses XFS, install the xfsdump utility, which is required for certain XFS operations:

# yum install xfsdump -y

Step 4 – Re‑mount and Verify

After shrinking, attempt to mount /home again:

# mount /home
mount: /dev/mapper/centos-home：不能读超级块

The error indicates the filesystem needs to be recreated; therefore, back up any data from /home before proceeding.

Once the backup is complete, format and mount the resized partition:

# mkfs.xfs /dev/mapper/centos-home
# mount /home

Result

The /home partition is now limited to 100 GB, freeing space for the root filesystem to be expanded. Remember to always back up critical data before resizing or reformatting partitions.