Understanding session behavior

Author: joshmaCreated Jun 24, 2016Updated Oct 29, 2024

Labelsquestion

I'm trying to understand when running dumb-init under a session (i.e. not using --single-child) is useful, and I'm having a hard time reproducing the problem case. Here's a script I'm running that just runs yes as both background and foreground:

#!/bin/sh
yes > /dev/null &
yes > /dev/null

And then I'm running dumb-init -c -- /script.sh:

$ ps aux | grep sh
...
docker   13014  0.8  0.0   1100     4 pts/0    Ss+  19:57   0:00 dumb-init -c -- /bin/sh script.sh
docker   13020  0.0  0.0   4448   776 pts/0    S+   19:57   0:00 /bin/sh script.sh
docker   13033  0.0  0.0   9760  1028 pts/1    S+   19:57   0:00 grep sh

$ ps aux | grep yes
...
docker   13021 99.2  0.0   4352   640 pts/0    R+   19:57   0:10 yes
docker   13022  101  0.0   4352   692 pts/0    R+   19:57   0:11 yes
docker   13039  0.0  0.0   9620   888 pts/1    R+   19:57   0:00 grep yes

When I run kill 13014, the sh process quits, and all yes processes quit as well. It's immediate, so this isn't the "TERM then wait 10s before KILL" behavior. This looks like good behavior, even though I'm using the -c flag. Am I incorrectly reproducing this?

Source: Yelp/dumb-init

View original on GitHub View discussion on GitHub