You shouldn't even need to boot with a LiveCD, simply boot your system with either the string 1
or the word single
at the end of your linux ...
stanza when GRUB2 initially is displayed.
Example
When booting the system if you access the boot menu options for the kernel from the GRUB2 menu, you can append the appropriate string at the end to gain single user mode access to your system.
linux /vmlinuz-3.13.5-101.fc19.x86_64 root=/dev/mapper/fedora_greeneggs-root ro rd.md=0 rd.dm=0 vconsole.keymap=us rd.lvm.lv=fedora_greeneggs/swap
rd.lvm.lv=fedora_greeneggs/root rd.luks=0 vconsole.font=latarcyrheb-sun16 rhgb quiet LANG=en_US.UTF-8 single
NOTE: You typically hit the e key and then arrow down to the linux ...
line adding the string "single" to the end. Then hit the F10 to boot it.
Once booted you should be able to access your /etc/shadow
file and remove the existing password from root's entry, making it blank. If you then reboot the system you should be able to get in with a blank password and use passwd
to reset it.