When Ubuntu rancher is installed, the Docker image restarts repeatedly, and the Rancher UI cannot be connected。
1、Ubuntu 18.04、20.04，Linux version 5.4.0-80-generic (buildd@lcy01-amd64-030) (gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04))
2、Docker version 20.10.7, build f0df350
3、docker logs ：Google Drive: Sign-in
As Vincent said this isn’t strictly a Rancher issue but I found a workaround by manually setting nf_conntrack_max to the value that Rancher was trying to set but being denied permission to do.
Looking at the logs for the container, I could see it wanted to set nf_conntrack_max to 327680 so I did
sudo sysctl -w net/netfilter/nf_conntrack_max=327680 then manually stopped and started the Rancher container, which resolved the issue for now.
See this GitHub issue - seems the issue is unresolved.
This solution also worked for me and I included it as part of cloud-init and a Systemd unit to ensure it’s persists across reboots (just bolt and braces).
It’s possible that Rancher Server v2.6.x will resolve this.