It is possible to upgrade to Debian 9 from Debian 8 using ssh.
This tutorial shows how to upgrade from Debian 8 Jessie Linux to Debian 9 Stretch using command line.
Using your country code in the file will speed up the package download.
Make sure you read the page before typing any one of the following commands.
Make a backup (I am using Rsnapshot) – it cannot be stressed enough how important it is to make a backup of your system before you do this.
Before you start with the upgrade, backup all critical data.
Thats especially the config data in the /etc directory and the user data in /home.
Done Building dependency tree Reading state information... sysv-rc sysvinit-utils tar task-english task-ssh-server tasksel tasksel-data tcpd telnet texinfo time traceroute tzdata ucf udev util-linux util-linux-locales vim vim-common vim-runtime vim-tiny w3m wget whiptail whois xauth xdg-user-dirs xkb-data xml-core xz-utils zlib1g .... Deferring configuration of apt-listchanges until python3 is available (Reading database ... He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector.