Live Resize of Logical Volume in RHEL/CentOS

The default installation of RHEL 6 and CentOS 6 will create separate LVM volumes for /home. This means much of your disk is allocated to /home when it could be used for something else. Keeping /home on a separate partition is a good idea for multi-user systems, but for machines that act as a service box, it may be wasted disk space. For example, here’s a system that has 50G partitioned for /home when it’s really not needed.

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$ df -h

2	Filesystem                  Size  Used Avail Use% Mounted on

3	/dev/mapper/vg_repo-lv_root 148G  113G   29G  80% /

4	tmpfs                       499M     0  499M   0% /dev/shm

5	/dev/sda1                   485M  156M  304M  34% /boot

6	/dev/mapper/vg_repo-lv_home 47G  181M   45G   1%  /home

To remove the logical volume that stores /home and add the free space to the root partition, follow these steps:

Note: Make sure you’re logged into the system at the console as a user whose homedir isn’t in /home. Logging in as root usually works.

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cd /

2	cp -Ra /home /home.bak  # Make a backup of home

3	umount /home

4	lvm lvremove /dev/vg_<hostname>/lv_home  # Remove the logical volume for home

5	lvm lvresize -l+100%FREE /dev/vg_<hostname>/lv_root  # Resize the root logical volume so it uses 100% of the now free space

6	resize2fs /dev/vg_<hostname>/lv_root  # Resize the filesystem to use the whole logical volume

7	mv /home.bak /home  # Restore the backup.

More Notes:

• This can be done on a live system as long as /home is not in use when you try to unmount it.
• You can also follow these steps to resize another logical volume if it has another name and isn’t in use.
• This may work with some adjustments on a RHEL/CentOS 5 system, I haven’t tried it though.
• you should definitly remove auto-mount information from /etc/fstab before rebooting the server.
• You’ll have to remove /home from /etc/fstab afterwards.