docker-sleep

#!/bin/sh

# Pause indefinitely, but exit immediately on receipt of SIGTERM, which is used
# by Kubernetes to signal to the container to exit[0].
#
# From the Bash Manual[1]:
#
# > If Bash is waiting for a command to complete and receives a signal for
# > which a trap has been set, the trap will not be executed until the command
# > completes.
#
# Therefore sleep not interrupted by signals. Instead background it and wait:
#
# > When Bash is waiting for an asynchronous command via the wait builtin, the
# > reception of a signal for which a trap has been set will cause the wait
# > builtin to return immediately with an exit status greater than 128,
# > immediately after which the trap is executed.
#
# This behaviour is common amongst POSIX compatible shells including bash,
# dash (debian), ash (alpine), and busybox.
#
# [0] https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#pod-termination
# [1] https://www.gnu.org/software/bash/manual/bash.html#Signals
trap : TERM
sleep infinity & wait