Rootless installer doesn't handle kernels without module support

[mhofman]

I'm trying to install docker rootless on a Chromebook.

The Linux environment runs inside an lxd container, itself inside a VM running a hardened kernel without module support. See https://chromium.googlesource.com/chromiumos/docs/+/master/containers_and_vms.md for more info.

The installer script checks for iptables support by checking if the module is loaded. This doesn't work on chromebooks because modules aren't available. However iptables is there and works (at least when run as root in the lxd container).

PS: regular docker runs perfectly fine, so I'll keep using that for the time being.

[tonistiigi]

Could you make a PR with extra detection for your system, or just override the validation for your system.

[halfninja]

I was in this situation and found the --skip-iptables option which is all that's needed to complete setup and have rootless working in Chrome OS.