[Guide] How to re-enable IPv6 if you disabled it during CT creation

[Quba1]

The described process can be deducted from the scripts, but I put it all here in one place to make it easier for others.

This guide shows how to re-enable IPv6 in your Proxmox container if you have disabled it during container creation using helper scripts.

Basically, the script disables IPv6 in the container by appending net.ipv6.conf.all.disable_ipv6 = 1 line in the /etc/sysctl.conf file inside your container. So to enable IPv6 again you just need to remove that line. Steps below describe how to do that.

0. (recommended) Backup or snapshot you container, if anything goes wrong you can restore it.
1. Enter your container shell. You can do that via SSH to go directly into the container or connect to your Proxmox node shell (via website or SSH) and then use pct enter <your_ct_id> command.
2. Open /etc/sysctl.conf in an editor. You can do that using command like vi /etc/sysctl.conf or nano /etc/sysctl.conf or whatever you prefer. Note that you need root/superuser access to edit that file, so use sudo (with caution!) as necessary.
3. Go to the end of the file and find line net.ipv6.conf.all.disable_ipv6 = 1. Then remove that line or add # in front of it to comment it out.
4. Save the file and close the editor.
5. (optional) Configure global IPv6 address. At that point, your container will most likely not have any global IPv6 address configured. If you need it, go to the Network page of your container on your Proxmox server website and configure the network interfaces as needed - either add a static address or select DHCPv6 or SLAAC.
6. Reboot your container - it will now have IPv6 connection if it's enabled in your network.