febootstrap-to-initramfs8

Usage

Overview

febootstrap-to-initramfs converts the filesystem created by febootstrap(8) into an initramfs image. This allows the new system to be booted on real hardware or inside a QEMU-based virtual machine.

An initramfs image is just a compressed cpio file, so you could uncompress it with gunzip(1) and use cpio(1) to convert it into other formats.

The permissions inside the initrd image are corrected automatically (see the discussion of fakeroot logfile in the febootstrap(8) page). You do not need to run this command as root.

Options

--files=filelist

"filelist" should be a file containing a list of the files to be added to the initramfs (one per line). Only those files are added and any others are ignored.

When the "--files" option is not given, all files in "DIR" are added to the initramfs image.

--nocompress

This prevents the initramfs image from being compressed.

Linux can boot from uncompressed initramfs images (in fact, faster), but they take up a lot more space on disk.

/init

Normal initramfs images start by executing the program or script called "/init". febootstrap does not create this script, so you may wish to, particularly for very minimal bootstraps that don't have the normal SysVinit/upstart machinery. It's also required if the kernel cannot find a "real" root filesystem (the root filesystem that we built and placed in an initramfs doesn't count).

Linux will try to run the following commands in turn, unless you override it using the "init=cmd" kernel option:

Memory requirements

Initramfs images are uncompressed by the kernel into memory. When booting the new system you will need at least enough free RAM to store the uncompressed filesystem plus extra to run any programs. Bear this in mind when creating very large filesystems.