[root@localhost]# df -h
Filesystem            Size  Used  Avail  Use%  Mounted on
/dev/mapper/centos-root 50G  22G  28G   3%  /
/dev/mapper/centos-home 1857G 33M 1857G  1%  /home
overlay 50G  22G  28G   3%  /var/lib/docker/overlay2/c2952714eb9921fe3ad9bfe4a35bd19b8879f4a9b61e76a50f8619b9a20f0b2b/merged
overlay 50G  22G  28G   3%  /var/lib/docker/overlay2/11f8e2a8da7f087573b35ff382059c233f2082dc6fb16b19f4131819eec18be1/merged

This guide will move space from the /home directory to the root partition.

Step 1: Backup the /home Directory

Before removing and recreating the /home logical volume, all data should be backed up first.

mkdir /mnt/home_backup

Explanation: Create a temporary directory at /mnt/home_backup to store the backup data.

rsync -avx /home/ /mnt/home_backup/

Explanation: Use the rsync tool to back up all data from the /home directory into /mnt/home_backup. The -a option enables archive mode, -v enables verbose output, and -x ensures only data from the current file system is synchronnized.

Step 2: Unmount the /home Logical Volume

Before deleting the logical volume, ensure that the /home volume is not in use.

umount /home

Explanation: Unmount the /home file system so it is no longer in use. If the system reports that the file system is busy, use the following command to force unmounting:

umount -l /home

Explanation: The -l option performs a "lazy" unmount, which immediately removes the mount point from the file system and unmounts it when it is no longer in use.

Step 3: Remove the /home Logical Volume

Once the /home volume has been successfully unmounted, delete the logical volume to free up space.

lvremove /dev/centos/home

Explanation: Delete the /home logical volume from the centos volume group, freeing up the disk space it occupied.

Step 4: Expand the Root Volume (or Another Logical Volume)

Use the freed space from the deleted /home logical volume to expand another logical volume (such as the root volume /).

lvextend -L +<size_to_add> /dev/centos/root</size_to_add>

Explanation: Add the specified <size_to_add></size_to_add> to the root logical volume /dev/centos/root. The + indicates an increase in the existing size, rather than setting a new fixed size.

xfs_growfs /dev/centos/root

Explanation: Extend the XFS file system to utilize the additional space allocated to the logical volume. This step ensures the file system can make use of the expanded space.

Step 5: Create a New /home Logical Volume

After expanding the other volume, use the remaining available space to create a new /home logical volume.

lvcreate -l 100%FREE -n home centos

Explanation: Create a new logical volume named home, using all the remaining space in the centos volume group. -l 100%FREE indicates using all the unused space in the volume group.

mkfs.xfs /dev/centos/home

Explanation: Format the new /dev/centos/home logical volume as an XFS file system so it can store data.

Step 6: Mount the New /home Logical Volume

Now, the new logical volume can be mounted to the /home directory.

mkdir /home

Explanation: Create the /home directory to serve as the mount point for the new logical volume.

mount /dev/centos/home /home

Explanation: Mount the new logical volume to the /home directory, making it part of the file system.

Step 7: Restore /home Data

Next, restore the previous backed-up /home data to the new logical volume.

rsync -avx /mnt/home_backup/ /home/

Explanation: Copy the backup data from /mnt/home_backup back to the new /home logical volume.

Step 8: Update /etc/fstab

To ensure the new /home logical volume is automatically mounted during boot, update the /etc/fstab file.

nano /etc/fstab

Explanation: Open the /etc/fstab file with the nano editor.

/dev/centos/home /home xfs defaults 0 0

Explanation: Add a line to /etc/fstab to ensure the /dev/centos/home logical volume is automatically mounted to /home on boot.

Save the file and exit the editor.

Step 9: Clean Up Backup Data

After confirming that the /home data has been successfully restored and the system is functioning properly, the backup data can be removed.

rm -rf /mnt/home_backup

Explanation: Delete the /mnt/home_backup directory and its contents to free up temporary storage space.

By following these steps, you can effectively back up the /home directory, remove and recreate the /home logical volume, expend another volume, and restore the data. This process helps manage and optimize system storage resources, ensuring data safety and system stability.