S3 Backup Backend (Minio)

Minio can be deployed as a Kuberentes service or as stand-alone in bare-metal environment. Since I want to use Minio Server for backing-up/restoring the cluster itself, I will go with a bare-metal installation, considering Minio as an external service in Kubernetes.

Official documentation can be used for installing stand-alone Minio Server in bare-metal environment.

For a more secured and multi-user Minio installation the instructions of this post can be used.

For installing Minio S3 storage server, I am using a VM (Ubuntu OS) hosted in Public Cloud (Oracle Cloud Infrastructure), but any linux server/VM that is not not part of the cluster can be used.

Minio installation and configuration tasks have been automated with Ansible developing a role: ricsanfre.minio. This role, installs Minio Server and Minio Client and automatically create S3 buckets, and configure users and ACLs for securing the access.

Minio installation (baremetal server)

  • Step 1. Create minio’s UNIX user/group

    sudo groupadd minio
    sudo useradd minio -g minio
  • Step 2. Create minio’s S3 storage directory

    sudo mkdir /storage/minio
    chown -R minio:minio /storage/minio
    chmod -R 750 /storage/minio
  • Step 3. Create minio’s config directories

    sudo mkdir -p /etc/minio
    sudo mkdir -p /etc/minio/ssl
    sudo mkdir -p /etc/minio/policy
    chown -R minio:minio /etc/minio
    chmod -R 750 /etc/minio
  • Step 4. Download server binary (minio) and minio client (mc) and copy them to /usr/local/bin

     wget https://dl.min.io/server/minio/release/linux-<arch>/minio
     wget https://dl.minio.io/client/mc/release/linux-<arch>/mc
     chmod +x minio
     chmod +x mc
     sudo mv minio /usr/local/bin/minio
     sudo mv mc /usr/local/bin/mc

    where <arch> is amd64 or arm64.

  • Step 5: Create minio Config file /etc/minio/minio.conf

    This file contains environment variables that will be used by minio server.

    # Minio local volumes.
    # Minio cli options.
    MINIO_OPTS="--address :9091 --console-address :9092 --certs-dir /etc/minio/ssl"
    # Access Key of the server.
    # Secret key of the server.
    # Minio server region
    # Minio server URL

    Minio is configured with the following parameters:

    • Minio Server API Port 9091 (MINIO_OPTS=”–address :9091”)
    • Minio Console Port: 9092 (MINIO_OPTS=”–console-address :9092”)
    • Minio Storage data dir (MINIO_VOLUMES): /storage/minio
    • Minio Site Region (MINIO_SITE_REGION): eu-west-1
    • SSL certificates stored in (MINIO_OPTS=”–certs-dir /etc/minio/ssl”): /etc/minio/ssl.
    • Minio server URL (MINIO_SERVER_URL): Url used to connecto to Minio Server API
  • Step 6. Create systemd minio service file /etc/systemd/system/minio.service

    ExecStartPre=/bin/bash -c "if [ -z \"${MINIO_VOLUMES}\" ]; then echo \"Variable MINIO_VOLUMES not set in /etc/minio/minio.conf\"; exit 1; fi"
    ExecStart=/usr/local/bin/minio server $MINIO_OPTS $MINIO_VOLUMES
    # Let systemd restart this service always
    # Specifies the maximum file descriptor number that can be opened by this process
    # Specifies the maximum number of threads this process can create
    # Disable timeout logic and wait until process is stopped

    This service start minio server using minio UNIX group, loading environment variables located in /etc/minio/minio.conf and executing the following startup command:

    /usr/local/minio server $MINIO_OPTS $MINIO_VOLUMES
  • Step 7. Enable minio systemd service

    sudo systemctl enable minio.service
  • Step 8. Create Minio SSL certificate

    In case you have your own domain, a valid SSL certificate signed by Letsencrypt can be obtained for Minio server, using Certbot.

    See certbot installation instructions in CertManager - Letsencrypt Certificates Section. Those instructions indicate how to install certbot using DNS challenge with IONOS DNS provider (my DNS provider). Similar procedures can be followed for other DNS providers.

    Letsencrypt using HTTP challenge is avoided for security reasons (cluster services are not exposed to public internet).

    If generating valid SSL certificate is not possible, selfsigned certificates with a custom CA can be used instead.

    Follow this procedure for creating a self-signed certificate for Minio Server

    1. Create a self-signed CA key and self-signed certificate

      openssl req -x509 \
             -sha256 \
             -nodes \
             -newkey rsa:4096 \
             -subj "/CN=Ricsanfre CA" \
             -keyout rootCA.key -out rootCA.crt
    2. Create a SSL certificate for Minio server signed using the custom CA

      openssl req -new -nodes -newkey rsa:4096 \
                  -keyout minio.key \
                  -out minio.csr \
                  -batch \
                  -subj "/C=ES/ST=Madrid/L=Madrid/O=Ricsanfre CA/OU=picluster/CN=s3.picluster.ricsanfre.com"
       openssl x509 -req -days 365000 -set_serial 01 \
             -extfile <(printf "subjectAltName=DNS:s3.picluster.ricsanfre.com") \
             -in minio.csr \
             -out minio.crt \
             -CA rootCA.crt \
             -CAkey rootCA.key

    Once the certificate is created, public certificate and private key need to be installed in Minio server following this procedure:

    1. Copy public certificate minio.crt as /etc/minio/ssl/public.crt

      sudo cp minio.crt /etc/minio/ssl/public.crt
      sudo chown minio:minio /etc/minio/ssl/public.crt
    2. Copy private key minio.key as /etc/minio/ssl/private.key

      cp minio.key /etc/minio/ssl/private.key
      sudo chown minio:minio /etc/minio/ssl/private.key
    3. Restart minio server.

      sudo systemctl restart minio.service

    To connect to Minio console use the URL https://s3.picluster.ricsanfre.com:9091

  • Step 9. Configure minio client: mc

    Configure connection alias to minio server.

    mc alias set minio_alias <minio_url> <minio_root_user> <minio_root_password>

Minio Configuration


The following buckets need to be created for backing-up different cluster components:

  • Longhorn Backup: k3s-longhorn
  • Velero Backup: k3s-velero
  • OS backup: restic

Buckets can be created using Minio’s CLI (mc)

mc mb <minio_alias>/<bucket_name> 

Where: <minio_alias> is the mc’s alias connection to Minio Server using admin user credentials, created during Minio installation in step 9.

Users and ACLs

Following users will be created to grant access to Minio S3 buckets:

  • longhorn with read-write access to k3s-longhorn bucket.
  • velero with read-write access to k3s-velero bucket.
  • restic with read-write access to restic bucket

Users can be created usinng Minio’s CLI

mc admin user add <minio_alias> <user_name> <user_password>

Access policies to the different buckets can be assigned to the different users using the command:

mc admin policy add <minio_alias> <user_name> user_policy.json

Where user_policy.json, contains AWS access policies definition like:

"Version": "2012-10-17",
"Statement": [
      "Effect": "Allow",
      "Action": [
      "Resource": [

This policy grants read-write access to bucket_name. For each user a different json need to be created, granting access to dedicated bucket. Those json files can be stored in /etc/minio/policy directory.

Last Update: Feb 17, 2023