Ubuntu 20.04 when I tried to install RabbitMQ it showing this error

Solution 1:

Please follow the official documentation: https://www.rabbitmq.com/install-debian.html#apt-quick-start-packagecloud

with a simple script, you can easily install rabbitmq on ubuntu.

for example:

#!/usr/bin/sh

sudo apt-get install curl gnupg apt-transport-https -y

## Team RabbitMQ's main signing key
curl -1sLf "https://keys.openpgp.org/vks/v1/by-fingerprint/0A9AF2115F4687BD29803A206B73A36E6026DFCA" | sudo gpg --dearmor > /usr/share/keyrings/com.rabbitmq.team.gpg
## Launchpad PPA that provides modern Erlang releases
curl -1sLf "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0xf77f1eda57ebb1cc" | sudo gpg --dearmor > /usr/share/keyrings/net.launchpad.ppa.rabbitmq.erlang.gpg
## PackageCloud RabbitMQ repository
curl -1sLf "https://packagecloud.io/rabbitmq/rabbitmq-server/gpgkey" | sudo gpg --dearmor > /usr/share/keyrings/io.packagecloud.rabbitmq.gpg

## Add apt repositories maintained by Team RabbitMQ
sudo tee /etc/apt/sources.list.d/rabbitmq.list <<EOF
## Provides modern Erlang/OTP releases
##
## "focal" as distribution name should work for any reasonably recent Ubuntu or Debian release.
## See the release to distribution mapping table in RabbitMQ doc guides to learn more.
deb [signed-by=/usr/share/keyrings/net.launchpad.ppa.rabbitmq.erlang.gpg] http://ppa.launchpad.net/rabbitmq/rabbitmq-erlang/ubuntu focal main
deb-src [signed-by=/usr/share/keyrings/net.launchpad.ppa.rabbitmq.erlang.gpg] http://ppa.launchpad.net/rabbitmq/rabbitmq-erlang/ubuntu focal main

## Provides RabbitMQ
##
## "focal" as distribution name should work for any reasonably recent Ubuntu or Debian release.
## See the release to distribution mapping table in RabbitMQ doc guides to learn more.
deb [signed-by=/usr/share/keyrings/io.packagecloud.rabbitmq.gpg] https://packagecloud.io/rabbitmq/rabbitmq-server/ubuntu/ focal main
deb-src [signed-by=/usr/share/keyrings/io.packagecloud.rabbitmq.gpg] https://packagecloud.io/rabbitmq/rabbitmq-server/ubuntu/ focal main
EOF

## Update package indices
sudo apt-get update -y

## Install Erlang packages
sudo apt-get install -y erlang-base \
                        erlang-asn1 erlang-crypto erlang-eldap erlang-ftp erlang-inets \
                        erlang-mnesia erlang-os-mon erlang-parsetools erlang-public-key \
                        erlang-runtime-tools erlang-snmp erlang-ssl \
                        erlang-syntax-tools erlang-tftp erlang-tools erlang-xmerl

## Install rabbitmq-server and its dependencies
sudo apt-get install rabbitmq-server -y --fix-missing

and ..

root@ubuntu-focal:/home/vagrant# rabbitmqctl status
Status of node rabbit@ubuntu-focal ...
Runtime

OS PID: 4038
OS: Linux
Uptime (seconds): 14
Is under maintenance?: false
RabbitMQ version: 3.9.4
Node name