actually, this is about 1/2 of exactly how it should be explained. just like your steps, only have the appropriate links and xterm codes with each.
sudo gainroot cd MyDocs
cp 00_disable_apn_ipv6 /etc/network/if-down.d
cp 00_enable_apn_ipv /etc/network/if-up.d
leafpad /etc/network/if-up.d/00_enable_apn_ipv6
### IPv4 APN value to hook up when activating IPv6 APN ### MY_IPv4_APN="sip.indt.intra"
### IPv6 APN value ### MY_IPv6_APN="ipv6.indt.intra"
### IPv6 APN username ### MY_IPv6_USERNAME="indt" ### IPv6 APN password ### MY_IPv6_PASSWORD="indt"
### Add prioritary IPv6-specific DNS server? ### ADD_IPv6_DNS="no"
### Prioritary IPv6-specific DNS server ### IPv6_DNS="2607:FB90:beef:3::2"
chmod ugo+x /etc/network/if-up.d/00_enable_apn_ipv6 chmod ugo+x /etc/network/if-down.d/00_disable_apn_ipv6