Booting into Single-User Mode
One of the advantages of single-user mode is that you do not need a boot diskette or CD-ROM; however, it does not give you the option to mount the file systems as read-only or not mount them at all.
if your system boots, but does not allow you to log in when it has completed booting, try single-user mode.
In single-user mode, your computer boots to runlevel 1
Your local file systems are mounted, but your network is not activated.
On Linux system using GRUB as the boot loader, 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 Enterprise Linux with the version of the kernel that you wish to boot and type a to append the line.
3. 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.
4. Back at the GRUB screen, type b to boot into single-user mode
On an x86 system using LILO as the boot loader, at the LILO boot prompt (if you are using the graphical LILO, you must press [Ctrl]-[x] to exit the graphical screen and go to the boot: prompt) type:
linux single