After the installer software loads into your machine RAM, the rescue environment prompt will appear on your screen. Rescue CentOS 7 System Rescue CentOS 7ProcessĤ. Here, just press key again to load the CentOS system to memory.

A new screen will appear with the message ‘ Press the Enter key to begin the installation process’. On the next screen choose Rescue a CentOS system option and press key to move further. From the first menu choose the Troubleshooting option and press key to continue. After the CentOS 7 bootable media has been detected, the first screen will appear in your machine monitor output. While the BIOS performs the POSTs tests, press a special key ( Esc, F2, F11, F12, Del depending on the motherboard instructions) in order to enter BIOS settings and modify the boot sequence so that the bootable DVD/USB image is booted first at machine start-up, as illustrated in the below image. Place the bootable image into your machine appropriate drive and reboot the machine. On the first step, download the latest version of CentOS 7 ISO image and burn it to a DVD or create a bootable USB stick. If from some reason the first 448 bytes are overwritten, the CentOS or Red Hat Enterprise Linux cannot be loaded unless you boot the machine with a CentOS ISO image in rescue mode or using other boot loading methods and reinstall the MBR GRUB boot loader.

Read Also: How to Rescue, Repair and Recover Grub Boot Loader in Ubuntu

The Grub boot loader stage one is installed on the first 448 bytes at the beginning of every hard disk, in an area typically known as the Master Boot Record ( MBR). A corrupted Grub boot loader makes a CentOS/RHEL system unable to boot and transfer the control further to Linux kernel. The GRUB boot loader can sometimes be damaged, compromised or deleted in CentOS due to various issues, such as hardware or software related failures or sometimes can be replaced by other operating systems, in case of dual-booting. In this tutorial we’ll cover the process of rescuing a corrupted boot loader in CentOS 7 or Red Hat Enterprise Linux 7 and recover the a forgotten root password.

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