init4boot

python based initramfs creator that supports NFS, iSCSI, LVM

Introduction

init4boot provides some scripts to generate a generic initramfs for different system. It was desined with debootstrap in mind: alternative implementations like initramfs-tools do - at least - have some problems with this.

Features & Differences to other implementations

There are some features which make init4boot unique. Other implementations handle this in a different way.

Features

• There is only one initrd. One init4boot initrd can be used to boot all. There is no need for creating new initrds for each system.
• Full debootstrap support. init4boot does not make any assumptions about the host or target system.
• Complete control. No assumptions, no heuristics what is or can in the host / target system. Everything can be specified on the command line or via an tftp server.

Drawbacks

• Because everything is in 'the' initrd, it's big. Booting takes longer.

HowTo

Creating

To create an initramfs, call the 'i4b-mkinitramfs' with the options:

• -o : the output file name
• -r : the root directory from which to take modules, libs and binaries.

The rootdir can be an installation done with 'debootstrap' or a copy of some existing system. When using a copy of the existing system, the following directories must be copied over (or must be able to access):

bin etc lib sbin usr

Note: It is very important, that there must no link to the outer world, e. g. lib -> /lib64. In this case the wrong files (from the build host) will be used.

Usage

To use the initrd created by init4boot, there is the need to adapt the boot kernel parameters. The location of the parameters are highly dependend which boot program you are using.

When you are using grub, you can find the kernel parameters typically in the file /boot/grub/grub.cfg. Have a look for menuentry and there for linux.

When you are using 'Das U-Boot' for embedded systems (like Raspberry Pi 2), the parameters are in the u-boot configuration file, like /boot/boot.cfg or /boot/firmware/boot.cfg. Do not forget to call the mkimage after changing this file.

Known to Run

This is a list of all systems where init4boot is known to work:

• Debian Jessie armhf on Raspberry Pi 2 with u-boot

Thanks

Some ideas and parts of the shell scripts are taken from the initramfs-tools. This implementation that can be found at http://anonscm.debian.org/cgit/kernel/initramfs-tools.git