[JENKINS-45888] Image.inside and Agent should use --init with 'docker run'

When Image.Inside() or an "agent { docker ... }" is used to docker run ... cat a docker container, it should always use the --init flag.

```
--init Run an init inside the container that forwards signals and reaps processes
```

This creates a PID 1 --init process that is sometimes needed to properly shutdown a container with multiple processes inside it.

A lot of build containers can start up a bunch of processes that may not be properly reaped or may not properly receive TERM and QUIT signals when trying to shutdown a container.

This should fix problems like JENKINS-37769 and JENKINS-32859

---
Originally reported by docwhat, imported from: Image.inside and Agent should use --init with 'docker run'

• status: Open
  
• priority: Minor
  
• component(s): docker-workflow-plugin
  
• label(s): docker
  
• resolution: Unresolved
  
• votes: 2
  
• watchers: 5
  
• imported: 2025-12-07
  

Raw content of original issue

When Image.Inside() or an "agent { docker ... }" is used to docker run ... cat a docker container, it should always use the --init flag.



--init  Run an init inside the container that forwards signals and reaps processes



This creates a PID 1 --init process that is sometimes needed to properly shutdown a container with multiple processes inside it.


A lot of build containers can start up a bunch of processes that may not be properly reaped or may not properly receive TERM and QUIT signals when trying to shutdown a container.


This should fix problems like JENKINS-37769 and JENKINS-32859