Fixing IPv6 on my Home Server

I have a home server to host several services for me and a few friends. I was setting up Passbolt, and it told me that IPv6 was not enabled on my machine. This issue hadn’t come up before while I had the server set up, so I was confused about why it came up now.

As is often the case with troubleshooting, I looked my problem up, searched through forums and blog posts, and even chatted with ChatGPT.

I first checked to see if Netplan had disabled DHCPv6. After looking, it didn’t explicitly say that DHCPv6 was disabled. However, I added the dhcp6: true line anyway.

I restarted my server to apply the changes, but the problem still persisted. I then went to see if the kernel was configured to have IPv6 enabled.

aura in 🌐 space in ~ on ☁️
➜ cat /boot/config-$(uname -r) | grep CONFIG_IPV6
CONFIG_IPV6=y
CONFIG_IPV6_ROUTER_PREF=y
CONFIG_IPV6_ROUTE_INFO=y
[...]

It sure looks to me like it was set to be enabled. The module must’ve not started correctly. I went to go check that too.

aura in 🌐 space in ~ on ☁️
➜ lsmod | grep ipv6
nf_defrag_ipv6         24576  1 nf_conntrack

Oh. So it’s loaded. Then why can’t I do anything with IPv6? I then reached out to a few of my friends on Discord because, at this point, I’ve exhausted what ChatGPT and forums have said to check and test. We rechecked everything aforementioned.

I got asked to check what /proc/cmdline said, and you wouldn’t guess what it output.

aura in 🌐 space in ~ on ☁️
➜ cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-5.15.0-78-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv ro ipv6.disable=1

We found the issue. A simple line was added to grub somehow. After a quick edit to /etc/default/grub, we were back on our way to setting up Passbolt.