Upgrade docker images to Ubuntu Focal

Closes gh-23492

ci/images/ci-image-jdk11/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:bionic-20200903
+FROM ubuntu:focal-20200916
 
 ADD setup.sh /setup.sh
 ADD get-jdk-url.sh /get-jdk-url.sh

ci/images/ci-image/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:bionic-20200903
+FROM ubuntu:focal-20200916
 
 ADD setup.sh /setup.sh
 ADD get-jdk-url.sh /get-jdk-url.sh

ci/images/setup.sh

@@ -5,8 +5,11 @@ set -ex
 # UTILS
 ###########################################################
 
+export DEBIAN_FRONTEND=noninteractive
 apt-get update
-apt-get install --no-install-recommends -y ca-certificates net-tools libxml2-utils git curl libudev1 libxml2-utils iptables iproute2 jq
+apt-get install --no-install-recommends -y tzdata ca-certificates net-tools libxml2-utils git curl libudev1 libxml2-utils iptables iproute2 jq
+ln -fs /usr/share/zoneinfo/UTC /etc/localtime
+dpkg-reconfigure --frontend noninteractive tzdata
 rm -rf /var/lib/apt/lists/*
 
 curl https://raw.githubusercontent.com/spring-io/concourse-java-scripts/v0.0.2/concourse-java.sh > /opt/concourse-java.sh

ci/scripts/detect-ubuntu-image-updates.sh

@@ -2,7 +2,7 @@
 
 ISSUE_TITLE="Upgrade Ubuntu version in CI images"
 
-ubuntu="bionic"
+ubuntu="focal"
 latest=$( curl -s "https://hub.docker.com/v2/repositories/library/ubuntu/tags/?page_size=1&page=1&name=$ubuntu" | jq -c -r '.results[0].name' | awk '{split($0, parts, "-"); print parts[2]}' )
 current=$( grep "ubuntu:$ubuntu" git-repo/ci/images/spring-boot-ci-image/Dockerfile | awk '{split($0, parts, "-"); print parts[2]}' )