febootstrap-to-initramfs (8) - Linux Manuals

febootstrap-to-initramfs: Convert febootstrap root to initramfs (cpio) file.


febootstrap-to-initramfs - Convert febootstrap root to initramfs (cpio) file.


 febootstrap-to-initramfs [--files=filelist] DIR > initrd.img


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.


"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.

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.


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:



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.


Richard W.M. Jones <rjones @ redhat . com>


(C) Copyright 2009 Red Hat Inc., <http://et.redhat.com/~rjones/febootstrap>.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.


febootstrap(8), cpio(1).