Also from: 8.5.4 → 8.5.5, 9.0.1 → 9.1.0

cd /root/
cp /var/lib/confluence/bin/setenv.sh /root/setenv.sh.bak_$(date +%F) && cp -r /var/lib/confluence/conf/ /root/confluence_conf_dir.bak_$(date +%F)
wget https://product-downloads.atlassian.com/software/confluence/downloads/atlassian-confluence-8.5.4-x64.bin && chmod +x atlassian-confluence-8.5.4-x64.bin

./atlassian-confluence-8.5.4-x64.bin

wget https://cdn.mysql.com//Downloads/Connector-J/mysql-connector-j-8.2.0.tar.gz

tar -C /var/lib/confluence/confluence/WEB-INF/lib -vxf mysql-connector-j-8.2.0.tar.gz mysql-connector-j-8.2.0/mysql-connector-j-8.2.0.jar --strip-components=1

cp server.xml /var/lib/confluence/conf/server.xml

systemctl restart confluence

• Installing Confluence server

• https://confluence.atlassian.com/doc/upgrading-confluence-4578.html