docs/debian9.md

Upgrading Debian 8 -> 9

Steps

Don't use tinc or any other VPN to connect to your server when doing a system upgrade.

1. Create backup (/etc, /home, /root, /var/lib/mysql, mysqldump, ...)
2. Update sources in /etc/apt/sources.list and /etc/apt/sources.list.d/ to stretch
3. apt update
4. apt upgrade
5. apt dist-upgrade
6. Fix errors and warnings and only then reboot
7. dpkg -l | grep -v ^ii should be empty or packages should be removed
8. reboot
9. test

Known problems

fail2ban

Some configuration changes, e.g. multiple ignore directives are no longer allowed, so

ignore = 127.0.0.1/8
ignore = 10.0.0.1/8

becomes

ignore = 127.0.0.1/8 10.0.0.1/8

IPv6

/etc/rc.local

/sbin/ip -6 addr add <ipv6-address>/64 dev eth0
/sbin/ip -f inet6 route add <ipv6-gateway> dev eth0		# this one is new
/sbin/route -A inet6 add default gw <ipv6-gateway> dev eth0

dnscrypt

Switch from init.d script to systemd. Systemd script can be obtained from the Arch Wiki