How to disable IPv6 on Debian Stretch 9.1?

Banana Pi SBCs design BPI-M2 Ultra / BPI-M2 Berry(A40i)
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How to disable IPv6 on Debian Stretch 9.1 ?

change: /etc/sysctl.conf

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

change: /proc/sys/net/ipv6/conf/all/disable_ipv6 to 1

result:

# netstat -tulpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      2594/sshd
tcp6       0      0 :::22                   :::*                    LISTEN      2594/sshd
udp        0      0 0.0.0.0:68              0.0.0.0:*                           2560/dhclient
udp        0      0 172.16.0.55:123         0.0.0.0:*                           2650/ntpd
udp        0      0 127.0.0.1:123           0.0.0.0:*                           2650/ntpd
udp        0      0 0.0.0.0:123             0.0.0.0:*                           2650/ntpd
udp        0      0 0.0.0.0:8472            0.0.0.0:*                           -
udp6       0      0 :::123                  :::*                                2650/ntpd