SYS: Extend existing unencrypted ext4-formatted logical volumes.

To extend an unencrypted ext4-formatted logical volume (here /dev/vg/lv_vol) by 1GB, type:

# lvextend --size +1G -r /dev/vg/lv_vol

Note: The file system is automatically extended (-r) without any need to unmount it.

To reduce the size of a logical volume (here by 1GB), you have to follow these steps:
Unmount the file system (here /dev/vg/lv_vol):

# umount /dev/vg/lv_vol

Reduce the logical volume (here /dev/vg/lv_vol) and the associated file system (-r):

# lvreduce --size -1G -r /dev/vg/lv_vol

Mount the file system (here /dev/vg/lv_vol):

# mount /dev/vg/lv_vol /mnt