==== Konfigurcja VPNa na potrzeby zajęć ====
(Dla zainteresowanych i dla mnie, żebym pamiętał co ustawiałem.)

Serwer działa na kontenerze LXC z system devuan (wersja beowulf):
  lxc create -n sieci-vpn -t download

Konfiguracja kontenera:
<code - /var/lib/lxc/sieci-vpn/config>
# Template used to create this container: /usr/share/lxc/templates/lxc-download
# Parameters passed to the template:
# Template script checksum (SHA-1): 1ba3a6d6544626d6e64c7b8f1a51f6022c5e5f8f
# For additional config options, please look at lxc.container.conf(5)

# Uncomment the following line to support nesting containers:
#lxc.include = /usr/share/lxc/config/nesting.conf
# (Be aware this has security implications)

# Distribution configuration
lxc.include = /usr/share/lxc/config/common.conf
lxc.arch = linux64

# Container specific configuration
lxc.rootfs.path = dir:/var/lib/lxc/sieci-vpn/rootfs
lxc.uts.name = sieci-vpn

# Network configuration
lxc.net.0.type = veth
lxc.net.0.link = br0
lxc.net.0.flags = up
lxc.net.0.hwaddr = 02:00:00:00:00:09

# this allows creating taps
lxc.cgroup.devices.allow = c 10:200 rwm

# let graphics work
lxc.mount.entry = /dev/dri dev/dri none bind,optional,create=dir
lxc.mount.entry = /tmp/.X11-unix tmp/.X11-unix none bind,optional,create=dir
</code>

Dodatkowe pliki wewnątrz kontenera:
<code - /etc/init.d/enable_tuntap>
#! /bin/sh
### BEGIN INIT INFO
# Provides:          enable_tuntap
# Required-Start:
# Required-Stop:
# Default-Start:     2 3 4 5
# Default-Stop:
# Short-Description:
### END INIT INFO

PATH=/sbin:/usr/sbin:/bin:/usr/bin

. /lib/init/vars.sh
. /lib/lsb/init-functions

do_start() {
        if ! [ -c /dev/net/tun ]
        then
                mkdir -p /dev/net
                mknod -m 666 /dev/net/tun c 10 200
        fi
}

case "$1" in
    start)
        do_start
        ;;
    restart|reload|force-reload)
        echo "Error: argument '$1' not supported" >&2
        exit 3
        ;;
    stop|status)
        # No-op
        exit 0
        ;;
    *)
        echo "Usage: $0 start|stop" >&2
        exit 3
        ;;
esac
</code>

<code - /etc/network/interfaces>
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

auto tap0
iface tap0 inet static
        address 10.0.9.1
        netmask 255.255.255.0
</code>

Pakiedy wewnątrz kontenera:
  apt update
  apt install openvpn
  update-rc.d enable_tuntap defaults
  wget https://multivnc-linux.surge.sh/multivnc-prerelease.deb
  apt install ./multivnc-prerelease.deb

Konfiguracja serwera:
<code - /etc/openvpn/sk2.conf>
mode server
tls-server

dev tap0

proto udp
port 1194

ping 30
push "ping 30"
ping-exit 180
push "ping-restart 120"

topology subnet
ifconfig 10.0.9.1 255.255.255.0
ifconfig-pool 10.0.9.2 10.0.9.99
client-to-client

log-append /var/log/openvpn-sk2.log

script-security 2
verify-client-cert none
auth-user-pass-verify /etc/openvpn/verify.pl via-file

## self sign:
## openssl genrsa -out sk2.key 4096
## openssl req -new -key sk2.key -out sk2.csr
## openssl x509 -signkey sk2.key -req -in sk2.csr -out sk2.crt
ca   /etc/openvpn/sk2.crt
cert /etc/openvpn/sk2.crt
key  /etc/openvpn/sk2.key
dh /etc/openvpn/dh2048.pem
</code>

Po uruchomieniu kontener startuje VPNa (debianopodobne systemy automatycznie uruchamiają każdy zainstalowany skrypt startowy).
Uruchomienie multivnc na komputerze hosta:
  xhost +
  LANG= lxc-attach sieci-vpn -- multivnc