Kubernetes Plugin: How to run commands within agent container as non-root?

[iris Jasper Orschulko]

I am trying to run a Pipeline in a Kubernetes agent, which needs to execute commands as non-root user. So I tried setting the securityContext of the Pod to 1000 (the default jenkins user) as described here: https://plugins.jenkins.io/kubernetes/. However, the user does not exist in the container within Kubernetes:

[Pipeline] {
[Pipeline] stage
[Pipeline] { (Yocto Build)
[Pipeline] container
[Pipeline] {
[Pipeline] script
[Pipeline] {
[Pipeline] sh

+ set -ex
+ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
_apt:x:100:65534::/nonexistent:/usr/sbin/nologin

However, when running the same image (jenkins/inbound-agent:4.3-4) in docker directly, there is a jenkins user:

sudo docker run -it --rm jenkins/inbound-agent:4.3-4 bash
jenkins@255a3961e41e:~$ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
_apt:x:100:65534::/nonexistent:/usr/sbin/nologin
jenkins:x:1000:1000:Jenkins user:/home/jenkins:/bin/sh

Any ideas why this might be the case? Is this intentional? If so, what would be the right way to run the container as non-root?

Best regards

Mit freundlichen Grüßen

Jasper Orschulko
Build- und Configurationsmanager

Tel. +49 30 58 58 14 265
Fax +49 30 58 58 14 999
Jasper.O...@irisgmbh.de

• • • • • • • • • • • • • • • • • • • • • • • • • •

iris-GmbH
infrared & intelligent sensors
Ostendstraße 1-14 | 12459 Berlin

Geschäftsführer
M.-O. Brammann | R. Bönick | A. Thun
Amtsgericht Berlin-Charlottenburg
HRB 41 448 | USt-ID-Nr. DE 137228225

www.irisgmbh.de

[Vincent Latombe]

> [Pipeline] container

What is your container definition? I really doubt it is the same image as what you're running through docker CLI.

Vincent

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[iris Jasper Orschulko]

Hi Vincent,

I am fairly certain, that the images are identical, as I used to pod image from the jenkins logs (jenkins/inbound-agent:4.3-4). The second image I used in the pipeline for the build process was https://hub.docker.com/r/kasproject/kas which also should have a non-root user (builder, uid 30000). I am not sure how Jenkins handles the containerisation, but unless there is some magic in the background I do not understand, it should be one of those images.

Best regards

Mit freundlichen Grüßen

Jasper Orschulko
Build- und Configurationsmanager

Tel. +49 30 58 58 14 265
Fax +49 30 58 58 14 999
Jasper.O...@irisgmbh.de

• • • • • • • • • • • • • • • • • • • • • • • • • •

iris-GmbH
infrared & intelligent sensors
Ostendstraße 1-14 | 12459 Berlin

Geschäftsführer
M.-O. Brammann | R. Bönick | A. Thun
Amtsgericht Berlin-Charlottenburg
HRB 41 448 | USt-ID-Nr. DE 137228225

www.irisgmbh.de

---

From: jenkins...@googlegroups.com [jenkins...@googlegroups.com] on behalf of Vincent Latombe [vincent...@gmail.com]
Sent: Friday, September 11, 2020 11:50 AM
To: Jenkins Users
Subject: Re: Kubernetes Plugin: How to run commands within agent container as non-root?

To view this discussion on the web visit https://groups.google.com/d/msgid/jenkinsci-users/CAH-zGCiznE%2Bu38q4NJ0Bj2k9PSgZ7iQvLJRemTO5c%2BbypGWYAw%40mail.gmail.com.

[Vincent Latombe]

Your second image runs as root and its /etc/passwd matches what you were seeing in your pipeline.

➭ docker run --entrypoint /bin/bash -ti kasproject/kas
root@ffa3dff671f9:/# cat /etc/passwd

root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
_apt:x:100:65534::/nonexistent:/usr/sbin/nologin

Vincent