reset root pw

rpm-based Distros(RedHat,CentOS,Fedora)
deb-baesd Distros(Debian,Ubuntu,Mint)
If you enter “passwd”or”vi”or”vim”,then may show “command not found”. because /usr isn’t mount.
If you /usr is in LVM, you can’t mount it because lvm is in /usr not in kernel. You need use nano,which is included in initramfs.

rpm-based Distros(RedHat,CentOS,Fedora)
boot to GRUB menu,choose the bar,push “e”,change “ro” to “rw init=/sysroot/bin/sh”,push ‘Ctrl+X’or’F10’ to boot as root

#chroot /sysroot
#passwd              ## enter root password
#touch /.autorelabel ## update SELinux info
#exit
#reboot

deb-baesd Distros(Debian,Ubuntu,Mint)
boot to GRUB menu,choose the bar,push “e”,change “ro” to “rw init=/bin/bash”,then push ‘Ctrl+X’or’F10’ to boot as root
then enter passwd to reset root password

If you enter “passwd”or”vi”or”vim”,then may show “command not found”. because /usr isn’t mount.

#cat /etc/fstab              ## (find the paratition with /usr
#mount /dev/"para_name" /usr ## (mount /usr;para_name like sda8
#passwd root                 ## (reset root password
#sync                        ## (update info

If you /usr is in LVM, you can’t mount it because lvm is in /usr not in kernel. Then you need use the very lightweight(about 200KB) editor nano,which is included in initramfs.

#cd /etc
#cp shadow shadow.bak ## (backup the shadows file
#nano shadow          ## (edit shadow with nano

the root’s info on the first line,del the shadow,push ‘Ctrl+X’,choose yes to save reboot,then the root can be log without password.Remenber run passwd!