openthread/environment docker rsyslogd: imklog: cannot open kernel log (/proc/kmsg): Operation not permitted

You will also get rid of this warning if you just comment out the line

module(load="imklog")

inside your Docker container (edit /etc/rsyslog.conf).

I doubt you want to read the kernel messages inside a container ;-)

@Reto's answer will work, but you will be editing that file every time you build your container. Put this in your Dockerfile and you're all set. The edit will be performed automatically while the container is being built.

RUN sed -i '/imklog/s/^/#/' /etc/rsyslog.conf