The Anaconda installation program’s rescue mode is a minimal Linux environment that can be booted from the Red Hat Enterprise Linux 7 (RHEL/CentOS) DVD or other boot media. It contains command-line utilities for repairing a wide variety of issues. This rescue mode can be accessed from the Troubleshooting submenu of the boot menu. In this mode, you can mount file systems as read-only or even to not mount them at all, blacklist or add a driver provided on a driver disc, install or upgrade system packages, or manage partitions.

How to boot a system into rescue mode using ISO DVD (RHEL / CentOS 7)

NOTE:
Anaconda rescue mode is different from rescue mode (an equivalent to single-user mode) and emergency mode, which are provided as parts of the systemd, system and service manager

To boot into Anaconda rescue mode, you must be able to boot the system using one Red Hat Enterprise Linux (RHEL) boot media, such as a minimal boot disc or USB drive, or a full installation DVD.

 

Booting into Anaconda Rescue Mode (Emergency Mode) in RHEL/CentOS 7

Boot the system from either minimal boot media, or a full installation DVD or USB drive, and wait for the boot menu to appear.

How to boot a system into rescue mode using ISO DVD (RHEL / CentOS 7)

 

In the boot menu for the installation media, select the Rescue an installed system option, or edit the kernel command line to include the word rescue.

How to boot a system into rescue mode using ISO DVD (RHEL / CentOS 7)

 

When prompted about mounting the disks for the target system to be rescued, select option 1 (Continue). This will mount the system under /mnt/sysimage.

How to boot a system into rescue mode using ISO DVD (RHEL / CentOS 7)

 

Press Enter to obtain a shell when prompted. This shell will live inside the installation/rescue environment, with the target system mounted under /mnt/sysimage.
This shell has a number of tools available for rescuing a system, such as all common file system, disk, LVM, and networking tools. The various bin directories of the target
system are added to the default executable search path (${PATH}) as well.

How to boot a system into rescue mode using ISO DVD (RHEL / CentOS 7)

 

Even if your file system is mounted, the default root partition while in Anaconda rescue mode is a temporary root partition, not the root partition of the file system used during normal user mode (multi-user.target or graphical.target). If you selected to mount your file system and it mounted successfully, you can change the root partition of the Anaconda rescue mode environment to the root partition of your file system by executing the following command:

How to boot a system into rescue mode using ISO DVD (RHEL / CentOS 7)

 

This is useful if you need to run commands, such as rpm, that require your root partition to be mounted as /. To exit the chroot environment, type exit to return to the prompt.

 

Lastly I hope the steps from the article to boot into rescue mode or emergency mode using DVD ISO image in RHEL or CentOS 7 Linux was helpful. So, let me know your suggestions and feedback using the comment section.

 

References:
Anaconda boot into rescue mode

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