Creating Debian Backports (snmpd on Bullseye)
Intro
A quick dump about backporting packages for Debian.
The issue was the bug in snmpd on Debian 11, where Docker and its dynamic network interfaces cause a crash.
The idea about a simple backport come from here.
So to create a backport of a package, use a clean VM with the correct Debian version (Debian 11 for this case).
Official documentation on backporting
Howto
# install tools for package creation
apt install packaging-dev debian-keyring devscripts equivs
# Find out which version is available in the Debian archive
rmadison snmpd --architecture amd64
# add the source where you found the package in our case "stable"
vim /etc/apt/sources.list
# update package list
apt update
# download package source
apt source snmpd/stable
# Install build dependencies
cd net-snmp-5.9.3+dfsg/
mk-build-deps --install --remove
# Indicate in the changelog a backport revision number
dch --bpo
# Test if we can successfully build the package
fakeroot debian/rules binary
# Build a package properly, without signing the package
dpkg-buildpackage --build=binary --unsigned-changes
# install
cd ..
dpkg -i snmpd_5.9.3+dfsg-2~bpo11+1_amd64.deb libsnmp40_5.9.3+dfsg-2~bpo11+1_amd64.deb