#### Beyond Linux® From Scratch (systemd Edition) - Version r13.0-491

### Chapter 3. After LFS Configuration Issues

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# Creating a Custom Boot Device

## Decent Rescue Boot Device Needs

This section is really about creating a rescue device. As the name rescue implies, the host system has a problem, often lost partition information or corrupted file systems, that prevents it from booting and/or operating normally. For this reason, you must not depend on resources from the host being "rescued". To presume that any given partition or hard drive will be available is a risky presumption.

In a modern system, there are many devices that can be used as a rescue device: floppy, cdrom, usb drive, or even a network card. Which one you use depends on your hardware and your BIOS. In the past, a rescue device was thought to be a floppy disk. Today, many systems do not even have a floppy drive.

Building a complete rescue device is a challenging task. In many ways, it is equivalent to building an entire LFS system. In addition, it would be a repetition of information already available. For these reasons, the procedures for a rescue device image are not presented here.

## Creating a Rescue Floppy

The software of today's systems has grown large. Linux 2.6 no longer supports booting directly from a floppy. In spite of this, there are solutions available using older versions of Linux. One of the best is Tom's Root/Boot Disk available at http://www.toms.net/rb/. This will provide a minimal Linux system on a single floppy disk and provides the ability to customize the contents of your disk if necessary.

## Creating a Bootable CD-ROM

There are several sources that can be used for a rescue CD-ROM. Just about any commercial distribution's installation CD-ROMs or DVDs will work. These include RedHat, Ubuntu, and SuSE. One very popular option is Knoppix.

Also, the LFS Community has developed its own LiveCD available at https://www.linuxfromscratch.org/livecd/. This LiveCD, is no longer capable of building an entire LFS/BLFS system, but is still a good rescue CD-ROM. If you download the ISO image, use xorriso to copy the image to a CD-ROM.

The instructions for using GRUB2 to make a custom rescue CD-ROM are also available in LFS Chapter 10.

## Creating a Bootable USB Drive

A USB Pen drive, sometimes called a Thumb drive, is recognized by Linux as a SCSI device. Using one of these devices as a rescue device has the advantage that it is usually large enough to hold more than a minimal boot image. You can save critical data to the drive as well as use it to diagnose and recover a damaged system. Booting such a drive requires BIOS support, but building the system consists of formatting the drive, adding GRUB as well as the Linux kernel and supporting files.

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