[Kubernetes cronjob] pg_isready only works interactively (pod user permissions maybe?)

Summary

TL;DR: pg_isready only seems to work when executed interactively in the pod, as opposed to when the pod is executed. This happens after I had to manually add the PGSSLMODE=require env variable because it was throwing a /root/.postgresql/postgresql.crt: Permission denied error.

Steps to reproduce

What I did was I:

Created the k8s job
Followed the steps here
After just setting the env variables listed above (MODE=MANUAL, MANUAL_RUN_FOREVER=FALSE, CONTAINER_ENABLE_SCHEDULING, and CONTAINER_ENABLE_MONITORING), it wouldn't start on its own (was waiting on user input).
Adding /etc/services.available/10-db-backup/run to the "command" field of the container definition resulted in a "no such file or directory" error.
I took inspiration from this comment which had me add the ['/init', 'backup-now'] commands which worked.
At that point, with all the envs loaded, I was getting a failed connection to my postgres server with /root/.postgresql/postgresql.crt: Permission denied being cited as the issue.
I added PGSSLMODE=require to the env list, and the error went away.
Now, I am facing the issue where pg_isready won't see that the server is ready. In order to debug, I grabbed the command that was being executed in the debug logs and ran it interactively in the pod with pg_isready --host=$DB01_HOST --port=$DB01_PORT --dbname=$DB01_NAME --username=$DB01_USER and it worked perfectly.

I suspect that this is a permissions issue with how the commands are being executed, but I'm not entirely sure.

I have the following k8s config:

apiVersion: batch/v1
kind: CronJob
metadata:
  name: postgres-storage-backup
  namespace: mastodon
spec:
  schedule: "30 1 * * *"
  concurrencyPolicy: Forbid
  suspend: false
  successfulJobsHistoryLimit: 1
  failedJobsHistoryLimit: 1
  jobTemplate:
    spec:
      template:
        metadata:
          name: postgres-storage-backup
        spec:
          volumes:
            - name: postgres-completion
              configMap:
                name: postgres-completion
                defaultMode: 0500
          containers:
            - name: postgres-storage-backup
              image: tiredofit/db-backup:4.1.3
              imagePullPolicy: IfNotPresent
              command:
                - /init
                - backup-now
              volumeMounts:
                - name: postgres-completion
                  mountPath: "/script"
              env:
                - name: DEBUG_MODE
                  value: "TRUE"
                - name: PGSSLMODE
                  value: "require"
                - name: MODE
                  value: "MANUAL"
                - name: MANUAL_RUN_FOREVER
                  value: "FALSE"
                - name: CONTAINER_ENABLE_SCHEDULING
                  value: "FALSE"
                - name: CONTAINER_ENABLE_MONITORING
                  value: "FALSE"
                - name: DEFAULT_POST_SCRIPT
                  value: "/script/postgres.sh"
                - name: DEFAULT_BACKUP_LOCATION
                  value: 'S3'
                - name: DEFAULT_S3_BUCKET
                  valueFrom:
                    configMapKeyRef:
                      name: storage-backup
                      key: postgres_bucket
                - name: DEFAULT_S3_KEY_ID
                  valueFrom:
                    configMapKeyRef:
                      name: storage-backup
                      key: DEFAULT_S3_KEY_ID
                - name: DEFAULT_S3_KEY_SECRET
                  valueFrom:
                    configMapKeyRef:
                      name: storage-backup
                      key: DEFAULT_S3_KEY_SECRET
                - name: DEFAULT_S3_REGION
                  valueFrom:
                    configMapKeyRef:
                      name: storage-backup
                      key: DEFAULT_S3_REGION
                - name: DEFAULT_S3_HOST
                  valueFrom:
                    configMapKeyRef:
                      name: storage-backup
                      key: DEFAULT_S3_HOST
                - name: DB01_TYPE
                  value: "pgsql"
                - name: DB01_HOST
                  valueFrom:
                    configMapKeyRef:
                      name: mastodon-env-tf
                      key: DB_HOST
                - name: DB01_PORT
                  valueFrom:
                    configMapKeyRef:
                      name: mastodon-env-tf
                      key: DB_PORT
                - name: DB01_NAME 
                  valueFrom:
                    configMapKeyRef:
                      name: mastodon-env-tf
                      key: DB_NAME
                - name: DB01_USER
                  valueFrom:
                    configMapKeyRef:
                      name: mastodon-env-tf
                      key: DB_USER
                - name: DB01_PASS 
                  valueFrom:
                    configMapKeyRef:
                      name: mastodon-env-tf
                      key: DB_PASS
          restartPolicy: OnFailure
  successfulJobsHistoryLimit: 1
  failedJobsHistoryLimit: 1

What is the expected correct behavior?

pg_isready sees that the server is up and backs it up

Relevant logs and/or screenshots

I've attached the debug logs with everything sensitive scrubbed: private-logs.txt

Environment

Image version / tag: tiredofit/db-backup:4.1.3
Host OS: k8s 1.30.2-do.0

Possible fixes

I've spent a fair amount of time debugging this, so I felt like there was just a point where it would be best to track my progress with a bug open

tiredofit / docker-db-backup