How to add an username when create a k8s pod - kubernetes

Question

I have a yaml file for creating k8s pod with just one container. Is it possible to pre-add an username and its password from yaml file during k8s pod creation?
I searched many sites and found the env variable. However, I could not make the pod as my wish. The pod's status is always showing Crashoff after pod creation.
Is it possible to pre-add an username and its password from yaml file during k8s pod creation?
Following are my yaml file:
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: centos610-sp-v1
spec:
replicas: 1
template:
metadata:
labels:
app: centos610-sp-v1
spec:
containers:
- name: centos610-pod-v1
image: centos-done:6.10
env:
- name: SSH_USER
value: "user1"
- name: SSH_SUDO
value: "ALL=(ALL) NOPASSWD:ALL"
- name: PASSWORD
value: "password"
command: ["/usr/sbin/useradd"]
args: ["$(SSH_USER)"]
ports:
- containerPort: 22
resources:
limits:
cpu: "500m"
memory: "1G"
---
apiVersion: v1
kind: Service
metadata:
name: centos610-sp-v1
labels:
app: centos610-sp-v1
spec:
selector:
app: centos610-sp-v1
ports:
- port: 22
protocol: TCP
nodePort: 31022
type: NodePort
---
Should I use specific command as
env:
- name: MESSAGE
value: "hello world"
command: ["/bin/echo"]
args: ["$(MESSAGE)"]
or
command: ["/bin/sh"]
args: ["-c", "while true; do echo hello; sleep 10;done"]
pod's status after get
root#zero:~/k8s-temp# kubectl get pod
NAME READY STATUS RESTARTS AGE
centos610-sp-v1-6689c494b8-nb9kv 0/1 CrashLoopBackOff 5 3m
pod's status after describe
root#zero:~/k8s-temp# kubectl describe pod centos610-sp-v1-6689c494b8-nb9kv
Name: centos610-sp-v1-6689c494b8-nb9kv
Namespace: default
Node: zero/10.111.33.15
Start Time: Sat, 16 Mar 2019 01:16:59 +0800
Labels: app=centos610-sp-v1
pod-template-hash=2245705064
Annotations: <none>
Status: Running
IP: 10.233.127.104
Controlled By: ReplicaSet/centos610-sp-v1-6689c494b8
Containers:
centos610-pod-v1:
Container ID: docker://5fa076c5d245dd532ef7ce724b94033d93642dc31965ab3fbde61dd59bf7d314
Image: centos-done:6.10
Image ID: docker://sha256:26362e9cefe4e140933bf947e3beab29da905ea5d65f27fc54513849a06d5dd5
Port: 22/TCP
Host Port: 0/TCP
Command:
/usr/sbin/useradd
Args:
$(SSH_USER)
State: Terminated
Reason: Completed
Exit Code: 0
Started: Sat, 16 Mar 2019 01:17:17 +0800
Finished: Sat, 16 Mar 2019 01:17:17 +0800
Last State: Terminated
Reason: Completed
Exit Code: 0
Started: Sat, 16 Mar 2019 01:17:01 +0800
Finished: Sat, 16 Mar 2019 01:17:01 +0800
Ready: False
Restart Count: 2
Limits:
cpu: 500m
memory: 1G
Requests:
cpu: 500m
memory: 1G
Environment:
SSH_USER: user1
SSH_SUDO: ALL=(ALL) NOPASSWD:ALL
PASSWORD: password
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-qbd8x (ro)
Conditions:
Type Status
Initialized True
Ready False
PodScheduled True
Volumes:
default-token-qbd8x:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-qbd8x
Optional: false
QoS Class: Guaranteed
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 22s default-scheduler Successfully assigned centos610-sp-v1-6689c494b8-nb9kv to zero
Normal SuccessfulMountVolume 22s kubelet, zero MountVolume.SetUp succeeded for volume "default-token-qbd8x"
Normal Pulled 5s (x3 over 21s) kubelet, zero Container image "centos-done:6.10" already present on machine
Normal Created 5s (x3 over 21s) kubelet, zero Created container
Normal Started 4s (x3 over 21s) kubelet, zero Started container
Warning BackOff 4s (x3 over 19s) kubelet, zero Back-off restarting failed container
2019/03/18 UPDATE
Although pre-add username and password from pod's yaml is not suggested but I just want to clarify how to use command & args from yaml file. Finally, I use following yaml file to create a username "user1" and its password "1234" successfully. Thank you all of you guys' great answer to make me more familiar with k8s about configMap, RBAC, container's behavior.
Actually, this link gave me a reference on how to use command & args
How to set multiple commands in one yaml file with Kubernetes?
Here are my final yaml file content:
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: centos610-sp-v1
spec:
replicas: 1
template:
metadata:
labels:
app: centos610-sp-v1
spec:
containers:
- name: centos610-pod-v1
image: centos-done:6.10
env:
- name: SSH_USER
value: "user1"
- name: SSH_SUDO
value: "ALL=(ALL) NOPASSWD:ALL"
- name: PASSWORD
value: "password"
command: ["/bin/bash", "-c"]
args: ["useradd $(SSH_USER); service sshd restart; echo $(SSH_USER):1234 | chpasswd; tail -f /dev/null"]
ports:
- containerPort: 22
resources:
limits:
cpu: "500m"
memory: "1G"
---
apiVersion: v1
kind: Service
metadata:
name: centos610-sp-v1
labels:
app: centos610-sp-v1
spec:
selector:
app: centos610-sp-v1
ports:
- port: 22
protocol: TCP
nodePort: 31022
type: NodePort
---

Answer 1

Keep username and password in a configMap or in a secret object. Load those values into container as environment variables
Follow the reference
https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/

Answer 2

If you want to add the user anyway , regardless of the fact that you can achive the same thing using A kubernetes native way , then
Please setup your user in the Docker image ( Dockerfile and then build it) instead.
Hope this helps.

Answer 3

2019/03/18 UPDATE
Although pre-add username and password from pod's yaml is not suggested but I just want to clarify how to use command & args from yaml file. Finally, I use following yaml file to create a username "user1" and its password "1234" successfully. Thank you all of you guys' great answer to make me more familiar with k8s about configMap, RBAC, container's behavior.
Actually, this link gave me a reference on how to use command & args
How to set multiple commands in one yaml file with Kubernetes?
Here are my final yaml file content:
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: centos610-sp-v1
spec:
replicas: 1
template:
metadata:
labels:
app: centos610-sp-v1
spec:
containers:
- name: centos610-pod-v1
image: centos-done:6.10
env:
- name: SSH_USER
value: "user1"
- name: SSH_SUDO
value: "ALL=(ALL) NOPASSWD:ALL"
- name: PASSWORD
value: "password"
command: ["/bin/bash", "-c"]
args: ["useradd $(SSH_USER); service sshd restart; echo $(SSH_USER):1234 | chpasswd; tail -f /dev/null"]
ports:
- containerPort: 22
resources:
limits:
cpu: "500m"
memory: "1G"
---
apiVersion: v1
kind: Service
metadata:
name: centos610-sp-v1
labels:
app: centos610-sp-v1
spec:
selector:
app: centos610-sp-v1
ports:
- port: 22
protocol: TCP
nodePort: 31022
type: NodePort
---