This flag seems to only disable ipv6 on the default Docker bridge network, not daemon-wide. At least per this discussion.

It’s in the dnsutils package.

Well crap. Do you have no ipv6 address now in ip addr?

Guess I gave Docker too much benefit of the doubt and assumed it should failover to v4 once v6 was disabled. Bad assumption on my part.

Could it be a DNS problem? If you dig registry-1.docker.io +short does it return an ipv4 or v6 address?

It looks like there have been sporadic reports of problems from people since last year.

Ok, so it’s probably using NetworkManager. I would try disabling it in /etc/NetworkManager/NetworkManager.conf by adding a block like:

[ipv6]
addr-gen-mode=stable-privacy
method=disabled

Then sudo systemctl restart NetworkManager. Can’t say for sure if this will work. I dislike using NetworkManager on my servers so I can’t test if this works. But hopefully the before/after of ip addr is different.

Although it looks like your ip addr output posted an hour or so ago doesn’t show any ipv6 addressing. Maybe the problem is solved now.

Different programs have different defaults.

But in your situation which would be more helpful - prevent this one docker command from using ipv6 (likely more difficult), or preventing all commands from using your broken ipv6 config (likely easier)?

I have no idea about the first. Maybe some people know this detail. But I’m sure that with a distro and version that you’re running, there are lots of people who could help with the second. Raspberry Pi 3B+ is the hardware. What software are you using?

Docker is a distraction in your problem description.

It’s like if you asked why the top gear in your car isn’t working and gave the model of car and engine type and gearbox. But it’s really that you’re stuck in slow traffic. Focus on the road name and destination to find a faster route.

For your problem, search for how to disable ipv6 for the Linux distribution and version that you have installed. You will find lots of guidance. Or share those details here for someone to help.

Or, better might be to see if there is a way to get ipv6 tunneling working on your connection. It may be possible even if the ISP is unhelpful.

Some routers advertise a routable link local.