Icingadb-redis install

I want to install icinga2 on ubuntu docker.

docker run -ti ubuntu:bionic bash

apt-get install icingadb-redis

But no package was found.

ubuntu :

lsb_release -a

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.6 LTS
Release: 18.04
Codename: bionic

vi /etc/apt/sources.list.d/bionic-icinga.list

deb Index of /ubuntu icinga-bionic main
deb-src Index of /ubuntu icinga-bionic main

apt-get update

Have I miss some steps?
I see the ‘icingadb-redis package provided by Icinga, which ships a current Redis Server version and is preconfigured for the Icinga DB components’ in doc.
If there has be a redis database on the monitored host, can I configure it connect to Icinga DB?
Or I install a redis alone, how to configure for the Icinga DB component? Is there some instruction? Thanks a lot!

Icinga DB is not officially supported on Ubuntu 18 Bionic. (Only the last two LTS releases are) Hence Icinga does not provide packages for it.

use ubuntu 20 or 22 lts
and add the official repository:

https://icinga.com/docs/icinga-2/latest/doc/02-installation/02-Ubuntu/

apt-get update
apt-get -y install apt-transport-https wget gnupg

wget -O - https://packages.icinga.com/icinga.key | apt-key add -

. /etc/os-release; if [ ! -z ${UBUNTU_CODENAME+x} ]; then DIST="${UBUNTU_CODENAME}"; else DIST="$(lsb_release -c| awk '{print $2}')"; fi; \
 echo "deb https://packages.icinga.com/ubuntu icinga-${DIST} main" > \
 /etc/apt/sources.list.d/${DIST}-icinga.list
 echo "deb-src https://packages.icinga.com/ubuntu icinga-${DIST} main" >> \
 /etc/apt/sources.list.d/${DIST}-icinga.list

apt-get update

If there has be a redis database on the monitored host, can I configure it connect to Icinga DB?

icingadb is not for the monitored hosts (agents)

if you setup you icinga server you can choose between ido and icingadb
if you setup a agent there is no need for that

the confusing part is that the icinga2 package for icinga2 is the same one.