run a shell in the docker host (use on dOckeR for mac or windoze)

a.sh

#!/bin/sh
# (in kubernetes, you'd use AllowPrivilegeEscalation probably, idk. exercise for the reader)

docker run -it \
    --privileged \
    --pid=host \
    alpine \
    nsenter -t 1 -m -u -n -i bash

# nsenter  # exec something in a namespace (analogous to su -c)
# -t 1   # take contexts from pid 1 (ie when we enter namespaces later, we are using the ones seen by pid 1)
# -m     # enter the pid 1 mount ns
# -u     # enter the pid 1 uts ns
# -n     # enter the pid 1 net ns
# -i     # enter the pid 1 ipc ns