Backup Postgres databases with Kubernetes CronJobs
A key part of operating any safe and reliable system is ensuring that there is a way to recover deleted or lost data in a prompt and consistent way. One key part of that is to maintain automatic backups that are recoverable and verifiable.
This is a quick and easy way to accomplish that goal, by using existing pieces of infrastructure that are common in production networks. There are countless ways to perform a backup, this is simply one of the “easiest” given these ingredients are available.
┌───────────┐ ┌─────────────┐
│ │ │ │
│ Postgres │ │ Backup S3 │
│ Database │ │ Bucket │
│ │ │ │
└───┬───────┘ └──────────▲──┘
│ │
│ │
│ │
│ │
│ │
┌──┼───────────────────────────┼──┐
│ │ Kubernetes Cluster │ │
│ │ │ │
│ │ ┌────────────────────┐ │ │
│ │ │ Backup-Worker │ │ │
│ └──► (CronJob) ┼───┘ │
│ │ │ │
│ └────────────────────┘ │
│ │
└─────────────────────────────────┘
Assumptions:
- You have a Kubernetes cluster
- You have a Postgres database
- You have access to an S3-like storage repository
- Most, or all, of this is in AWS
If these assumptions are not true, it’s still possible to get some value from this, though you’ll have to make some adjustments.
An important caveat: This should only really be done with small-ish databases, where having a complete export is particularly advantageous. If it takes longer than about 15 minutes to run a sqldump, you should consider more advanced techniques to accomplish this.
Also, while there are backup & restore tools inside of RDS, Aurora, and other managed database solutions, I still find it massively valuable to have access to a true SQL dump at times. Your milage may vary, of course.
To get this all working:
It takes a few steps to wire everything up just right:
- Build a container with the required tools for the backup
- Provision the bucket and lifecycle policy for data retention
- Set up service account & permissions to allow the Pod to upload backups
- Generate an encryption key to encrypt backups
- Configure the backup script
- Set up the CronJob to execute the backup on a daily schedule
Security and data integrity will be the foremost priorities throughout this process, so principles of least privilege and encryption at rest are fundamentally important concepts.
Build a custom container image
Whenever working with a container orchestration system like Kubernetes, it’s always best to use purpose-built tools whenever possible. Not only does this reduce image pull times, it also reduces the number of possible vulnerabilities, and therefore the number of times your “security guy” nags you. 😉
This toolbox image, backup-worker has tools for Postgresql and Kafka, as well as AWS utilities.
FROM debian:12-slim
RUN apt update && \
apt install -y curl gnupg openssl awscli postgresql-client-15 kcat
A basic build task in GitHub Actions can build and push the image:
...
- name: Docker Login - GitHub Container Repo
uses: docker/login-action@v1
with:
registry: ghcr.io
username: ${{ github.repository_owner }}
password: ${{ secrets.GITHUB_TOKEN }}
- name: Push image
run: |
IMAGE_ID=ghcr.io/${{ github.repository }}/backup-worker
docker tag image $IMAGE_ID:latest
docker push $IMAGE_ID:latest
docker tag image $IMAGE_ID:$GITHUB_SHA
docker push $IMAGE_ID:$GITHUB_SHA
A full config is out of scope for this post, but there are plenty of examples for building and uploading a docker image to the registry of your choice.
Create the required AWS Resources
When creating a simple backup like this, I like to configure the permissions such that the backup process itself cannot delete the backup files. Instead, S3’s lifecycle rules will rotate out old backups, in this case after 90 days.
The importance of this setup is that it prevents a malicious or accidental process within the kubernetes cluster from deleting historic backups. This has long been a key pillar of ransomware attacks, and one that is not possible here by compromising the backup worker process.
More sophisticated rules are also possible with this config, like adding prefix rules for daily/weekly/monthly retention. For simplicity, this will just delete any files older than 90 days:
resource "aws_s3_bucket" "db_backups" {
bucket = "my-database-backups-bucket"
tags = local.tags
}
resource "aws_s3_bucket_lifecycle_configuration" "db_backups_lifecycle" {
bucket = aws_s3_bucket.db_backups.id
rule {
id = "1"
filter {
prefix = ""
}
status = "Enabled"
expiration {
days = 90
}
}
}
Set up the AWS Permissions
This cluster has IAM Roles for Service Accounts (IRSA) enabled, so mapping individual pods identities to AWS identities is very simple. In this case, the Pod’s ServiceAccount has access to only read & write data to the bucket created in the previous step.
#IAM policy for S3 access - Allows read/write only
resource "aws_iam_policy" "s3_backup_service" {
name = "s3_backup_service"
policy = jsonencode({
Version = "2012-10-17"
Statement = [
{
Effect = "Allow"
Action = [
"s3:GetObject",
"s3:PutObject"
]
Resource = [
"${aws_s3_bucket.db_backups.arn}/*"
]
},
{
Effect = "Allow"
Action = [
"s3:ListBucket"
]
Resource = [
aws_s3_bucket.db_backups.arn
]
}
]
})
}
# IAM role for backup-service
resource "aws_iam_role" "s3_backup_service" {
name = "s3_backup_service"
assume_role_policy = jsonencode({
Version = "2012-10-17"
Statement = [
{
Effect = "Allow"
Principal = {
Federated = module.eks.oidc_provider_arn
}
Action = "sts:AssumeRoleWithWebIdentity"
Condition = {
StringEquals = {
"${module.eks.oidc_provider}:aud" = "sts.amazonaws.com",
"${module.eks.oidc_provider}:sub" = "system:serviceaccount:default:backup-service"
}
}
},
]
})
}
resource "aws_iam_role_policy_attachment" "s3_backup_service" {
role = aws_iam_role.s3_backup_service.name
policy_arn = aws_iam_policy.s3_backup_service.arn
}
Note that this references some specific pre-existing pieces of infrastructure. If you have not built your cluster using Terraform, replace module.eks.oidc_provider_arn and module.eks.oidc_provider with the correct values.
The ServiceAccount is also created by Terraform:
# The Service Account in Kubernetes
resource "kubernetes_service_account" "backup-service" {
metadata {
name = "backup-service"
namespace = "default"
annotations = {
"eks.amazonaws.com/role-arn" = aws_iam_role.s3_backup_service.arn
}
}
}
Secrets
For good security hygiene, secrets should always be kept safe and out of cleartext.
For simplicity, we’ll put all of the configuration in this Secret. In a real cluster, these would likely be pulled from multiple Secrets, and ideally managed by an external secrets provider!
---
apiVersion: v1
kind: Secret
metadata:
name: backup-secrets
stringData:
S3_BUCKET: "my-database-backups-bucket"
AES_KEY: "super-secure-aes-key"
PGHOST: "example.123456789012.ca-central-1.rds.amazonaws.com"
PGPORT: "5432"
PGUSER: "backup-role"
PGPASSWORD: "super-secure-password"
Database Backup script
Note that this script will backup multiple databases on the same server or RDS cluster. Simply replace database1 database2 ... with your database name(s).
As an additional security measure, all backup files are symmetrically encrypted with AES before being uploaded to the bucket.
This script takes two variables as inputs:
S3_BUCKETAES_KEY
Both are passed in by Secrets via the Pod’s configuration.
#!/bin/bash
set -euo pipefail
trap 'echo "[!] Error executing backup!"' ERR
AES_KEY_HASH=$(echo -n "${AES_KEY}" | sha256sum)
echo "[+] Encryption key sha256: ${AES_KEY_HASH}"
NOW=$(date +"%Y-%m-%d-%H-%M-%S")
mkdir /backups
echo "[+] Backing up data from server: ${PGHOST}"
for db in database1 database2 database3; do
backup_file_path="/backups/${db}_${NOW}.enc"
echo "[+] Backing up database ${db}..."
pg_dump ${db} | gzip | \
gpg --batch -c --passphrase "${AES_KEY}" - > ${backup_file_path}
if [ ! -s "$backup_file_path" ]; then
echo "[!] Error backing up. File is 0kb or does not exist"
exit 1
fi
echo "[+] Done."
done
echo "[+] List of backups:"
ls -lash /backups
echo "[+] Uploading backup files to S3 bucket: ${S3_BUCKET}"
aws s3 sync /backups/ s3://${S3_BUCKET}/
The script is put inline inside the ConfigMap manifest, backup-database .
---
apiVersion: v1
kind: ConfigMap
metadata:
name: backup-database
data:
backup.sh: |
#Script in-line here!
The CronJob and Pod config
The backup-worker image from earlier can be used here to execute the backup job using a Kubernetes CronJob:
---
apiVersion: batch/v1
kind: CronJob
metadata:
name: database-backup
spec:
schedule: "0 0 * * *" #Midnight UTC
successfulJobsHistoryLimit: 2
failedJobsHistoryLimit: 2
concurrencyPolicy: "Forbid"
jobTemplate:
spec:
backoffLimit: 3
template:
spec:
nodeSelector:
type: "private"
containers:
- name: backup
image: backup-worker:latest
command: ["/bin/bash", "/scripts/backup.sh"]
envFrom:
- secretRef:
name: "backup-secrets"
volumeMounts:
- name: backup-database
mountPath: /scripts
restartPolicy: Never
serviceAccountName: "backup-service"
volumes:
- name: backup-database
configMap:
defaultMode: 0644
name: backup-database
The backup in action
Simply wait until midnight UTC, and the CronJob timer will execute the backup.
Okay, fine, I’m impatient too - Let’s trigger it manually.
kubectl create job --from=cronjob/database-backup database-backup-123456-abcd
Once started, you can follow along with the backup task:
kubectl logs -f database-backup-123456-abcd
The output should look something like this:
[+] Encryption key sha256: 2fb2cfa7bac33a8b02a4b0ce8f85c46feb90f4ea20697c52fb84a855baf9202b -
[+] Backing up data from server: example.123456789012.ca-central-1.rds.amazonaws.com
[+] Backing up database example...
[+] Done.
[+] List of backups:
total 123M
16K drwxr-xr-x. 2 root root 16K Feb 19 00:00 .
0 drwxr-xr-x. 1 root root 70 Feb 19 00:00 ..
123M -rw-r--r--. 1 root root 123M Feb 19 00:00 example_2026-02-19-00-00-01.enc
[+] Uploading backup files to S3 bucket: my-database-backups-bucket
upload: backups/example_2026-02-19-00-00-01.enc to s3://my-database-backups-bucket/example_2026-02-19-00-00-01.enc
Likewise, the file will be present inside the s3 bucket if listed using the awscli tool:
$ aws s3 ls s3://my-database-backups-bucket
...
2026-02-19 19:00:36 12345678 example_2026-02-19-00-00-01.enc
And just like that, future backups will work exactly the same, on a daily schedule.
Bonus: Backup Kafka topic
Using the building blocks laid out above, it’s also quite simple to set up a backup for small Kafka topics. An example script:
Input variables:
S3_BUCKETKAFKA_BROKERSAES_KEY
#!/bin/bash
set -euo pipefail
trap 'echo "[!] Error executing backup!"' ERR
NOW=$(date +"%Y-%m-%d-%H-%M-%S")
mkdir /backups
echo "[+] Backing up topics..."
TOPICS=(
"_schemas"
"Foo.bar.v1"
)
for topic in "${TOPICS[@]}"; do
echo "[+] Backing up topic ${topic}..."
backup_file_path="/backups/${topic}_${NOW}.enc"
kcat -C -b "${KAFKA_BROKERS}" -t "${topic}" -e | \
gpg --batch -c --passphrase "${AES_KEY}" - > ${backup_file_path}
if [ ! -s "$backup_file_path" ]; then
echo "[!] Error backing up. File is 0kb or does not exist"
exit 1
fi
done
echo "[+] List of backups:"
ls -lash /backups
echo "[+] Uploading backup files to S3 bucket: ${S3_BUCKET}"
aws s3 sync /backups/ s3://${S3_BUCKET}/
Be careful with Kafka - only backup topics this way that are relatively small and contain precious data.
What happens when it goes wrong?
There are of course many potential failure modes for any backup system. Fortunately, this has some advantages over some traditional ways of executing a backup.
First, the Kubernetes scheduler will always ensure that the Job is run exactly once on its schedule, no matter how many nodes are running. And if it is interrupted, it will simply start over again reducing the chances of a partial backup run.
Another advantage is that the way failures are reported is consistent with the rest of the kubernetes metrics. Any issue during backup will cause an exit code >1, marking the Job as Failed, and hopefully sending an alert through your monitoring system! Instead of relying on email or slack webhooks, this ties in wonderfully with existing and trusted monitoring tech.
Logging is also a nice bonus - since everything goes through stdout, it will all get picked up by your log monitor and make discovery and troubleshooting a breeze.
All in all, it’s a quick and easy way to get a level of backups working without the fuss of a 3rd party service. All the pieces (probably) already exist, so adding this onto a cluster is basically free. And we love those types of easy wins, don’t we?