ELBE Quickstart

You have probably received a root-filesystem, which has been built with ELBE. Additionally you should have an XML file describing the root-filesystem.

This quickstart guide describes the steps necessary to rebuild the root-filesystem from the XML file and to simple modifications.

Steps necessary

  1. install Debian 8 (Jessie) on your Host
  2. install ELBE on Host Linux
  3. generate the initvm running the buildenvironment
  4. build the root-filesystem inside the initvm

Steps 1 and 2 need only be performed once.

Note

When Debian is running inside a VM (vmware etc), you need to make sure, that nested KVM is working.

Customisation of the build

The ELBE XML can contain an archive, which can contain configuration files, and additional software. This archive is extracted onto the target-image during the buildprocess. It allows you to override any file, which needs to be different from the default Debian Install.

This guide also explains how the archive can be extracted from the XML file, and vice versa.

ELBE allows to manipulate the generated root-filesystem through a set of <finetuning> rules. We also describe, how these can be used to add a user, change directory permissions, and remove files from the root-filesystem.

Installing ELBE

There are several possibilities to install ELBE. The simplest method is by installing prebuilt binary packages via Linutronix package repository on a Debian 8 (Jessie) system.

But ELBE can also be installed from git.

Binary Debian packages

The latest packages for elbe reside in the following repository

http://debian.linutronix.de/elbe
http://debian.linutronix.de/elbe-common

Create the file /etc/apt/sources.list.d/elbe.list with the following contents:

deb http://debian.linutronix.de/elbe stretch main
deb http://debian.linutronix.de/elbe-common stretch main

Add a repository key to the list of trusted keys (as root):

$ wget -q -O - http://debian.linutronix.de/elbe-common/elbe-repo.pub | apt-key add -

Then run (as root):

$ apt-get update
$ apt-get install elbe

Git Version

If you can not use Debian Jessie, you can also checkout the current ELBE source-code via git from github.

$ git clone https://github.com/Linutronix/elbe.git
Cloning into 'elbe'...
remote: Counting objects: 5435, done.
remote: Compressing objects: 100% (8/8), done.
remote: Total 5435 (delta 1), reused 0 (delta 0), pack-reused 5427
Receiving objects: 100% (5435/5435), 1.94 MiB | 1.92 MiB/s, done.
Resolving deltas: 100% (3943/3943), done.
Checking connectivity... done.
$ cd elbe
$ ls
AUTHORS  ChangeLog  COPYING  debian  dockerfile  docs  elbe   elbepack
examples INSTALL    Makefile README  setup.py    test  THANKS TODO

ELBE can run without being installed from the git checkout. Just note that file paths are different under this situation.

elbe -> ./elbe
/usr/share/doc/elbe-doc/examples -> examples/

Create initvm and submit XML files

The first thing you need to do is set up a virtual-machine for generating root-filesystems.

This virtual-machine is referred to as “initvm”. You will want your initvm to be the same architecture as your workstation. This allows using hardware accelerated virtualization implemented by kvm.

In order to be able to work with virtual machines as a regular user, that user needs to be added to some groups depending on Debian version:

For Debian/stretch, jessie-backports, and newer:

$ adduser <youruser> libvirt $ adduser <youruser> libvirt-qemu

For jessie and older:

$ adduser <youruser> kvm $ adduser <youruser> libvirt

$ elbe initvm create --directory=initvm
/home/torbenh/elbe/elbe/initvm
gpg: keyring `/tmp/tmpPfPXt4/secring.gpg' created
gpg: keyring `/tmp/tmpPfPXt4/etc/apt/trusted.gpg.d/linutronix-elbe.gpg' created
gpg: key 22BB8F84: public key "ELBE Devel (Linutronix ELBE developers) <elbe-devel@linutronix.de>" imported
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)
--2015-08-17 15:26:26--  http://debian.linutronix.de/elbe/elbe-repo.pub
Resolving debian.linutronix.de (debian.linutronix.de)... 2001:470:1f0b:db:abcd:42:0:1, 62.245.132.108
Connecting to debian.linutronix.de (debian.linutronix.de)|2001:470:1f0b:db:abcd:42:0:1|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1763 (1.7K)
Saving to: ‘/tmp/tmpPfPXt4/tmpkey.gpg’

/tmp/tmpPfPXt4/tmpkey.gpg             100%[========================================================================>]   1.72K  --.-KB/s   in 0s

2015-08-17 15:26:26 (346 MB/s) - ‘/tmp/tmpPfPXt4/tmpkey.gpg’ saved [1763/1763]

...

Installing the base system  ... 17%... 20%... 30%... 40%... 50%... 60%... 70%... 83%... 91%... 100%
Configuring apt  ... 16%... 25%... 32%... 41%... 50%... 66%... 75%... 83%... 91%... 100%
Select and install software  ... 10%... 26%... 31%... 40%... 50%... 61%... 70%... 80%... 90%... 100%
Installing GRUB boot loader  ... 16%... 33%... 50%... 66%... 83%... 100%
The system is going down NOW!.. 14%... 23%... 33%... 42%... 52%... 61%... 71%... 80%... 90%
Sent SIGTERM to all processes
Sent SIGKILL to all processes
Requesting system reboot
[  589.432092] Restarting system.
mkdir -p .stamps
touch .stamps/stamp-install-initial-image

This creates an “initvm” subdirectory and builds the initvm inside this directory.

Submitting an XML file

Submitting an XML file triggers an image build inside the initvm. Once the initvm has been created and is running, you can submit XML files using

$ elbe initvm submit --directory=initvm /usr/share/doc/elbe-doc/examples/rescue.xml
Build started, waiting till it finishes
project still busy, waiting
project still busy, waiting

...

project still busy, waiting
project still busy, waiting
project still busy, waiting

Build finished !


ELBE Package validation
=======================


Package List validation
 ----------------------

No Errors found

Getting generated Files

Saving generated Files to /home/torbenh/elbe/elbe/elbe-build-20150817-155038
source.xml      (Current source.xml of the project)
rescue.cpio     (Image)
validation.txt  (Package list validation result)
elbe-report.txt         (Report)
log.txt         (Log file)

The result of the build is stored in elbe-build-<TIMESTAMP> below your current working directory.

Ports opened by initvm

The initvm will open port 7587 on localhost. This is used by the elbe tools on your host to communicate with the initvm.

Advanced usage

ELBE Archive

The ELBE XML file contains an archive which is extracted into the root-filesystem during the image generation phase.

It is acessed with the following commands:

$ elbe get_archive fun.xml archive.tar.bz2

It is a normal tar.bz2 which can be manipulated and reinjected into the XML:

$ mkdir arch
$ tar xvfj archive.tar.bz2 -C arch
$ echo hello > arch/hello
$ elbe chg_archive fun.xml arch

Adding packages to the “list of packages to install”

The XML file contains a list of packages to install <pkg-list> in the <target> XML node. Inserting a line containing

<pkg>util-linux</pkg>

will add the util-linux package to the target-rfs.

Using the finetuning rules

An ELBE XML file can contain a set of finetuning rules. Finetuning is used to customize the target-rfs, e.g. remove man-pages. Here is an example finetuning from /usr/share/doc/elbe-doc/examples/elbe-desktop.xml:

<finetuning>
        <rm>var/cache/apt/archives/*.deb</rm>
        <adduser passwd="elbe" shell="/bin/bash">elbe</adduser>
</finetuning>

rm

The <rm> node removes files from the target-rfs.

adduser

The adduser node allows to create a user. The following example creates the user elbe with the password foo.

It is also possible to specify groups the new user should be part of:

<adduser passwd="foo" shell="/bin/bash" groups="audio,video,dialout">elbe</adduser>

Changing ownership of directories or files

There is currently no special finetuning node for chmod and chown. These commands needs to be specified via the command tag, which allows running any command that is available in the target-rfs.

<command>chown elbe:elbe /mnt</command>
<command>chmod 777 /mnt</command>

Further Example

A more complete example can be found in the ELBE overview document that is installed at /usr/share/doc/elbe-doc/elbeoverview-en.html

Using the Elbe Pbuilder Feature

Since Version 1.9.2, elbe is able to create a pbuilder Environment. You can create a pbuilder for a specific xml File inside the initvm.

The repositories and architecture specified in the xml File will be used to satisfy build dependencies. Pbuilder will only build debianised Software.

Note

Currently only source formats 3.0 (native) and 3.0 (git) are supported and tested. 3.0 (quilt) does not work.

A pbuilder instance is always associated with a project inside the initvm. The pbuilder create command will write the project uuid to a file, if instructed to do so.

pbuilder build works like pdebuild, in that it uploads the current working directory into the initvm pbuilder project, and then builds it using the pbuilder instance created earlier.

Here is an example:

$ elbe pbuilder create --xmlfile fun.xml --writeproject fun.prj
$ cd program
$ elbe pbuilder build --project `cat ../fun.prj` --output ../out

Custom Repository

You might have your own packages which should be installed into your image. This can be done with a custom repository. You can use reprepro to create your own repository.

Repository Key

Because the repository needs to be signed using gpg, a key needs to be generated.

-> gpg --default-new-key-algo rsa4096 --gen-key
gpg (GnuPG) 2.1.18; Copyright (C) 2017 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Note: Use "gpg --full-generate-key" for a full featured key generation dialog.

GnuPG needs to construct a user ID to identify your key.

Real name: Torben Hohn
Email address: torben.hohn@linutronix.de
You selected this USER-ID:
    "Torben Hohn <torben.hohn@linutronix.de>"

Change (N)ame, (E)mail, or (O)kay/(Q)uit? O
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
gpg: key 68E68615BB6CB47C marked as ultimately trusted
gpg: directory '/home/torbenh/.gnupg/openpgp-revocs.d' created
gpg: revocation certificate stored as '/home/torbenh/.gnupg/openpgp-revocs.d/CF837F1AAAC35E084062AE4468E68615BB6CB47C.rev'
public and secret key created and signed.

Note that this key cannot be used for encryption.  You may want to use
the command "--edit-key" to generate a subkey for this purpose.
pub   rsa4096 2018-10-08 [SC] [expires: 2020-10-07]
      CF837F1AAAC35E084062AE4468E68615BB6CB47C
      CF837F1AAAC35E084062AE4468E68615BB6CB47C
uid                      Torben Hohn <torben.hohn@linutronix.de>

Please note the keyname (here CF837F1AAAC35E084062AE4468E68615BB6CB47C). This keyname can then be used to export the public key into a repo.pub file.

gpg --export --armor CF837F1AAAC35E084062AE4468E68615BB6CB47C > repo.pub

reprepro configuration

To create your own repository with reprepro you need only the distributions configuration file. For an amd64 and source repository for Debian stretch it might look as follows:

Origin: mylocal
Label: mylocal
Suite: stable
Codename: stretch
Architectures: amd64 source
Components: main
Description: my local repo
SignWith: CF837F1AAAC35E084062AE4468E68615BB6CB47C

**Note**

the ``SignWith:`` field needs to be the key of the previously
generated key.

Now place the distributions file in a conf named directory. also put repo.pub into your repo directory.

repo/
├── conf
│   └── distributions
└── repo.pub

insert pkgs into repo

To include packages in your repository you might use the following command from inside the repo directory:

$ reprepro include stretch ../path/to/your/*.changes

To use this repository from ELBE you need a webserver. Simply place the repository inside the document root of your webserver.

If the webserver is running on the same machine as the initvm you can use the following to access the repository:

<url-list>
        <url>
                <binary>http://LOCALMACHINE/repo/ jessie main</binary>
                <source>http://LOCALMACHINE/repo/ jessie main</source>
                <key>http://LOCALMACHINE/repo/repo.pub</key>
        </url>
</url-list>

ELBE replaces the string LOCALMACHINE with the ip address of your machine. If you use an external machine as webserver you need to replace LOCALMACHINE with the name or the ip of it.

Now you can install packages from your custom repository the same way you can install from any other repository.