# Example - Using Fluid to access non-root user's data

If the user data could only be access by specific uid, Runtime's 'RunAs' parameter should be set to let specific user run distributed data caching engine, to access underlying data.

This document demonstrates the above features with a simple example.

# Prerequisites

Please refer to Fluid installation documentation (opens new window) to complete installation.

# Running Example

Create a non-root user

$ groupadd -g 1201 fluid-user-1 && \
useradd -u 1201 -g fluid-user-1 fluid-user-1

The above command creates a non-root userfluid-user-1

Create a directory that belongs to the user

$ mkdir -p /mnt/nonroot/user1_data && \
echo "This is fluid-user-1's data" > /mnt/nonroot/user1_data/data1 && \
chown -R fluid-user-1:fluid-user-1 /mnt/nonroot/user1_data && \
chmod -R 0750 /mnt/nonroot/user1_data

The above command creates a directory user1_data belonging to fluid-user-1 in the /mnt/nonroot directory, We will use the data1 file in the user1_data directory to represent the data owned by fluid-user-1

$ ls -ltR /mnt/nonroot

Using the above command, you will see the following results

/mnt/nonroot/:
total 4
drwxr-x--- 2 fluid-user-1 fluid-user-1 4096 9月  27 16:45 user1_data

/mnt/nonroot/user1_data:
total 4
-rwxr-x--- 1 fluid-user-1 fluid-user-1 28 9月  27 16:45 data1

Create Dataset and AlluxioRuntime resource object

$ cat<<EOF >dataset.yaml
apiVersion: data.fluid.io/v1alpha1
kind: Dataset
metadata:
  name: nonroot
spec:
  mounts:
    # Specify the directory you just created as the mount point
    - mountPoint: local:///mnt/nonroot/
      name: nonroot
  # Ensure that the data cache is placed at the node where the /mnt/nonroot directory exists
  nodeAffinity:
    required:
      nodeSelectorTerms:
        - matchExpressions:
            - key: nonroot
              operator: In
              values:
                - "true"
---
apiVersion: data.fluid.io/v1alpha1
kind: AlluxioRuntime
metadata:
  name: nonroot
spec:
  replicas: 1
  tieredstore:
    levels:
      - mediumtype: SSD
        path: /var/lib/docker/alluxio
        quota: 2Gi
        high: "0.95"
        low: "0.7"
  # start Alluxio as the fluid-user-1 user
  runAs:
    uid: 1201
    gid: 1201
    user: fluid-user-1
    group: fluid-user-1
  fuse:
    args:
    - fuse
    - --fuse-opts=kernel_cache,ro,max_read=131072,attr_timeout=7200,entry_timeout=7200,max_readahead=0
EOF

In the above yaml configuration file, we will mount the directory we just created (/mnt/nonroot ') in the same way as the Fluid host directory. For more information about Fluid mount host directory, please refer to example - use Fluid to accelerate host directory

In addition, in spec.runAs we have set user information such as uid, which means that we are going to start the caching engine as a fluid-user-1 user to provide distributed caching capabilities

Log into the Application

$ kubectl exec -it nginx -- bash

$ id

Using the above command, you will see the following results:

uid=1201 gid=1201 groups=1201

This indicates that we started the application as a user with uid of 1201

Access Data

$ ls -ltR /data

Using the above command, you will see the following results:

/data/:
total 1
drwxr-xr-x 1 root root 1 Sep 27 08:45 nonroot

/data/nonroot:
total 1
drwxr-x--- 1 1201 1201 1 Sep 27 08:45 user1_data

/data/nonroot/user1_data:
total 1
-rwxr-x--- 1 1201 1201 28 Sep 27 08:45 data1

As you can see, Fluid exposes data belonging to a non-root user to applications that require it in the manner of passthrough, and the file information for the user's data does not change

Of course, the user is free to access the data:

$ cat /data/nonroot/user1_data/data1

Using the above command, you will see the following results:

This is fluid-user-1's data

# Environment Cleanup

$ kubectl delete -f .
$ rm -rf /mnt/nonroot
$ userdel fluid-user-1

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