In RedHat systems, single user mode is often used for system recovery, file system repair and resetting lost root password. Here we will resetting lost root password.
Step 1: In your boot menu press e for editing the boot options, and find your kernel parameter start with vmlinuz.
Step 3 : find ro and replace it with rw init=/sysroot/bin/sh. Press ctrl+x for proceeding.
Step 4 : chroot your Linux System and reset root password.