Add additional space to ext4 filesystem in RHEL

 To add additional space to an ext4 filesystem on a Red Hat Enterprise Linux (RHEL) system, you can use the following steps:

1. Use the command df -h to check the current usage and available space on the filesystem.
2. Use the command fdisk -l to check the available disk space on the system.
3. If there is free space on the disk, you can use the command fdisk /dev/sda (replacing /dev/sda with the appropriate device name) to create a new partition with the free space.
4. Use the command mkfs.ext4 /dev/sdaX (replacing /dev/sdaX with the appropriate device name) to create a new ext4 filesystem on the new partition.
5. Use the command mount /dev/sdaX /mnt (replacing /dev/sdaX and /mnt with the appropriate device name and mount point) to mount the new filesystem.
6. Use the command df -h again to check the new available space on the filesystem.
7. If you want to mount this filesystem automatically during boot, you should add an entry in the /etc/fstab file.

Please, be aware that this is a dangerous operation, if any mistake happens, it can cause data lost. It's strongly recommended to backup your data before doing this operation.