====== Reset root password on Redhat/CentOS ======

===== Solution 1 =====

Instead of starting with a kernel defined on the list, press **c** for command or **e** for edit the current line

add at the end of the line of default kernel: **rd.break**
Ex:
  linux   /boot/vmlinuz-3.16.7-21-default root=UUID=b5f92fce-af22-474c-9996-c66c087e2ea7  ${extra_cmdline}  quiet resume=/dev/system/swap splash=silent quiet showopts psmouse.proto=imps rd.break

then ctrl+x to start

Check the filesystems, you 'll see /sysroot is mounted in readonly (ro)
<cli prompt='#'>
# mount
</cli>

Remount the root filesystem in readwrite:
<cli prompt='#'>
# mount -o remount,rw /sysroot
</cli>

Chroot and change password
<cli prompt='#'>
# chroot /sysroot
# passwd
</cli>

Sometimes it is necessary to relabel the complete filesystem although this should only be necessary when enabling **SELinux** after it has been disabled or when changing the SELinux policy from the default targeted policy to strict. To automatically relabel the complete filesystem upon reboot, do:
<cli prompt='#'>
# touch /.autorelabel

# exit
# exit
</cli>

===== Solution 2 =====

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/sec-terminal_menu_editing_during_boot#sec-Recovering_Root_Password