What purpose does using exec in docker entrypoint scripts serve?

Question

For example in the redis official image:

https://github.com/docker-library/redis/blob/master/2.8/docker-entrypoint.sh

#!/bin/bash
set -e

if [ \"$1\"         


        

Answer 1

Without exec, the parent shell process survives and waits for the child to exit. With exec, the child process replaces the parent process entirely so when there's nothing for the parent to do after forking the child, I would consider exec slightly more precise/correct/efficient. In the grand scheme of things, I think it's probably safe to classify it as a minor optimization.

without exec

• parent shell starts
• parent shell forks child
  • child runs
  • child exits
• parent shell exits

with exec

• parent shell starts
• parent shell forks child, replaces itself with child
• child program runs taking over the shell's process
• child exits