Documentation and Helper Scripts to Install Debian with active LACP

This is basically what I did and wrote when I had to install a server via the manufacture-provided Remote Console whereas the server's only network connection were two bonded/teamed network interfaces which were configured to use LACP on the switch side.

And since the Debian Installer doesn't support LACP, we need to reorder some stuff and trick the netinst installer image into configuring the network, but not using it.

And since usually the only option to get files on to the new server via Remote Console but without network is via some local ISO image mounted via the web interface of the Remote Console, the script in this repo creates an ISO image which contains all the .deb files needed to get LACP up and running, including some tools to debug low-level networking as well as the possibility to add additional packages for your own convenience.

Prerequisites

• Debian Installer images, either the free version without non-free firmware blobs or the non-free version with non-free firmware blobs

• Needs to be run on the same Debian (or Derivative) release as the target release. (Most of the documentation assumes this to be Debian Stable in general and Debian 11 Bullseye specifically.)

• The following packages need to installed:

  • genisoimage

• Clone this repo: git clone https://github.com/xtaran/create-ifenslave-iso.git

• Change into the newly checked out working copy: cd create-ifenslave-iso.

• Have look at the script and the create a packages.local file if you want additional packages in your ISO image. See packages.local.example for an example for such a file.

  I recommend to add your favourite editor (in case it isn't one of Debian's default editors, namely vim-tiny or nano) and its non-default dependencies.

• Run ./create-ifenslave-iso.sh

You should have gotten a file named e.g. ifenslave-bullseye.iso if you ran the script on Debian 11 Bullseye.

Workflow

Basic Installation

Use the installer as you're used to do, but:

• Either just configure one interface statically, or
• Don't configure network at all.

Finish everything else.

Reboot into the newly installed system which still has no working network connection.

Mount the ISO and install all the packages on it.

Mount the newly generated ISO image via Remote Console's media management.

Log in as root (or as your user and then use sudo if you prefered that at installation time).

Run these commands with root privileges:

mount -o ro /media/cdrom
dpkg -i /media/cdrom/*.deb

Configure the Network and the APT Mirror

You can either edit the files /etc/network/interfaces and /etc/apt/sources.list by hand or use the example files included in the ISO (i.e. /media/cdrom/interfaces and /media/sources.list) and modify them as needed:

You can safely overwrite /etc/apt/sources.list with the file included in the ISO as the generated one won't contain anything useful which isn't in here, too (except maybe if you didn't want security updates — and you do want them ;-) or if you enabled the updates repo.

cp -v /media/sources.list /etc/apt
editor /etc/apt/sources.list

You might want to change the used generic mirror with a local mirror.

Be more careful with the /etc/network/interfaces file. I recommend to only append the file included in the ISO:

cat /media/cdrom/interfaces >> /etc/network/interfaces
editor /etc/network/interfaces

You especially need to edit the following sections:

• If you've configured a static IP address, copy the parts from the configured hardware interface to the section of the bond0 interface and remove or comment our the remaining original interface section.

• If you've configured DHCP, just remove or comment out the full original interface section.

• In any case edit the file and make sure the line with the keyword slaves lists the actual interface names on which the LACP is configured.

Check if ifup bond0 gives you a working network connection. If not, check what part of the configuration might be wrong. tcpdump and ethtool were installed before for debugging such cases.

Apply Security Updates

Run e.g.

apt update
apt upgrade
reboot

(Reboot only necessary if there were security updates to the init system, kernel or libc.)

Author

Axel Beckert [email protected] for the ETH Zurich IT Security Center.

Copyright

© 2022 Axel Beckert [email protected], ETH Zurich IT Security Center

License

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 3 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, see https://www.gnu.org/licenses/.