Best if important stuff is backed up first and custom apt sources disabled.nnapt updatenapt upgradencp /etc/apt/sources.list /etc/apt/sources.list.orignsed -i ‘s/stretch/buster/g’ /etc/apt/sources.listndiff sources.list.orig sources.list to verify the changenTo kick off the upgrade, apt update && apt upgradenFinally, apt dist-upgradenrebootnafter reboot, verify with lsb_release -a