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Using Nextcloud as front end for Allas storage system

Motivation: Allas is a general purpose storage system for research data. It can be used with tools based on Swift and S3 protocols. However, in many cases, using Allas directly trough S3 or Swift is limited by the rather plain structure of user management and by the fact that the access is based on personal CSC user accounts.

Using Nextcloud server as a front end allows you to create and manage your own user base for your Allas storage area and control the access to different datasets and storage areas. Further, Nextcloud provides several user interfaces (including a WWW-interface and a cell phone app) that are often easier to use and more flexible to use that native Swift or S3 applications.

In this document we show a simple use case with the following steps:

  1. Launch a new Ubuntu18 Virtual Machine
  2. Install a Nextcloud server into the new VM
  3. Link The Nextcloud server is linked to a data bucket in Allas
  4. New Nextcloud user account is created for an external user

1. Launch a new Ubuntu18 Virtual Machine

First, launch a new Ubuntu18 based server in cPouta service. See instructions in the cPouta documentation and in tutorial video.

In most cases the combination of “standard small” flavor and Ubuntu18.04 image is sufficient.

When you create the security group for the VM, the instructions above show how port 22 is opened for ssh access. In this case, use the same procedure to open port 443 (https), too, as it will be used to access the Nextcloud server.

2. Setting up a Next Cloud sever in the VM

Open a terminal connection to your server (ssh or Putty) to install the Nextcloud server. First, it is good to update the Ubuntu system:

sudo apt-get update
In this example we use snap as it provides an easy way to install Nextcloud. You can do the installations with just few commands.

First do the next-cloud installation with command: 

sudo snap install nextcloud
Then, Nextcloud administration account is created. In the command below the account name is defined to be ncadmin with password 1Hu9kgFsN. 
sudo nextcloud.manual-install ncadmin 1Hu9kgFsN
Next you need to enable https with self signed certificate. Self signed certificates are sufficient for testing, but for production you should use real certificates (e.g. lets-encrypt instead of self-signed). 
sudo nextcloud.enable-https self-signed

As a last step. add the IP-address of your Nextcloud server to the list of trusted domains. The IP-address is the Floating IP address that you assigned for the VM and that you used to open the terminal connection. For example the case of IP:86.50.252.77 the definition could be done with command: 

sudo nextcloud.occ config:system:set trusted_domains 1 --value=86.50.252.77

Now you should be able to connect your Nextcoud server running in https://ip-of-your-VM

So in this example: https://86.50.252.77

If the connection web interface fails check that:

  • you are using the right protocol and ip address
  • port number 443 and your local IP address (not the server IP) is defined in the cPouta security group and that this security group is in use
  • your browser accepts self-signed certificates

Nextcloud software is modular, it can be extended with Nextcloud Apps. Once you have the Nextcloud up and running, it is a good practise to check what Apps are enabled and how different features are configured to work. You can do this in the Nextcloud user interface when you are loggind in as admin. If you wish, you can also start this by running a CSC provided script that disables a few and configures some Apps in order to make the Nextcloud less overloaded with features for this kind of Allas front end testing. The script can be downloaded and run like this:

curl https://raw.githubusercontent.com/CSCfi/allas-cli-utils/master/nextcloud_snap/clean_nextcloud_snap >clean_nextcloud_snap
chmod +x clean_nextcloud_snap
./clean_nextcloud_snap

To be able to link Allas to your Nextcloud server, you must have a valid S3 key pair and a ready made data bucket in Allas. The bucket can be empty or it can already contain some data objects.

You can do this things for example in puhti.csc.fi with commands:

1. Setting up the connection:

   module load allas
   allas-conf --mode s3cmd

2. Creating a new empty bucket

s3cmd mb s3://your-proj-num-nextcloud
In this example we are using project 2001234 so the bucket name could be:

2001234-nextcloud

3. Printing out the keys

grep key $HOME/.s3cfg

Now return to the Nextcloud WWW-interface and log in as the admin. Click the round symbol on the right end of the blue menu bar and select +Apps from the pop-up menu.

From the appearing application list enable External storage support.

Then click the round symbol again and open settings .

In the settings panel on the left side, scroll to the Administration section add select: External storages .

Open the Add storage menu and select : Amazon S3

This opens a definition menu here you need to file following parameters:

  • Folder name: display name for the allas bucket (2001234-nextcloud)
  • Bucket: The bucket you just created or some older bucket.
  • Host:a3s.fi
  • Port: 443
  • Region: US
  • Enable SSL
  • Access key: from the output of the grep command above
  • Secret key: from the output of the grep command above

Then go to the External storages in your Personal settings and click the line containing the external folder name just created to ensure that the storage works.

If you now move to the Files tool in the main menu (blue bar on the top), you should see an new external storage folder named as defined above.

Now you can click this folder and start uploading and downloading data from and to this Allas bucket using the Nextcloud interface.

4. Create new Nextcloud user account for an external user

The Nextcloud admin account can create new users and user groups to the Nextcloud server. Click the round symbol on the right end of the blue menu bar and select Users from the pop-up menu.

First we create a new user group by clicking Add group. Here we name the group as “users” and confirm the creation request by typing the password of Nextcloud admin.

Then a new user is created by clicking add user User name and password needs to be defined for the user and the new account is added to group Users.

Finally, we need to allow this new user to access the External storage (the bucket from Allas). To do that, go back to the Settings view and reopen the External storages settings from the Administration tools.

Now in the “Available for” column, click the definition field. This lists the users and user groups. Choose either the user or user group to allow the new user to access the Allas bucket. You can define both read and write permissions or you can also give just read-only access to a user or user group. These options are set with the menu that opens from the three dots next to the definition field.

Now you can send the account information to the new user and he/she will be able to use Nextcloud to upload and download data to the data bucket that was linked to the Nextcloud server. Note, that this user doesn't need to have CSC account, a Nextcloud account is enough.