If you are using GRUB, use the following steps to boot into single-user mode:
1. If you have a GRUB password configured, type p and enter the password.
2. Select Red Hat Linux with the version of the kernel that you wish to boot and type e for edit. You will be presented with a list of items in the configuration file for the title you just selected.
3. Select the line that starts with kernel and type e to edit the line.
4. Go to the end of the line and type single as a separate word (press the [Spacebar] and then type single). Press [Enter] to exit edit mode.
5. Back at the GRUB screen, type b to boot into single user mode.
type # linux single