Injecting files in Ironic

Hello world

Let us start with the case from the tutorial. Imaging we want to change the message of the day to something positive:

Hello Ironic World!

For the list of deploy steps we'll use this file (inject_files.json):

[
  {
    "interface": "deploy",
    "step": "inject_files",
    "args": {
      "files": [
        {
          "path": "/etc/motd",
          "content": "SGVsbG8gSXJvbmljIFdvcmxkIQo="
        }
      ]
    },
    "priority": 50
  }
]

What is the priority and why 50? Read the deploy steps tutorial! Everything else should be more or less self-explanatory.

The metalsmith CLI does not have support for deploy steps yet, so start the deployment manually using the new --deploy-steps argument:

$ SSH_KEY=$(cat ~/.ssh/id_ed25519.pub)
$ baremetal node set <node> --instance-info image_source=file:///httpboot/centos8.qcow2
$ baremetal node deploy <node> \
    --config-drive '{"meta_data": {"public_keys": {"0": "'"$SSH_KEY"'"}}}' \
    --deploy-steps inject_files.json
$ watch baremetal node show <node> --fields provision_state deploy_step last_error

$ DIB_RELEASE=8 disk-image-create -o centos8-uefi centos vm openssh-server block-device-efi
$ sudo cp centos8-uefi.qcow2 /httpboot

Once the provision state is active, we can figure out the IP address and log into the instance:

$ ssh centos@<IP>
<..>
Hello Ironic World!
[centos@localhost ~]$

Target partition

What if we need to specify where to put the file? I'm struggling to invent an actual real-life example for it, so let us write a file to the EFI partition just because we can!

But how do we know where it will be located? Your image will probably give you a clue. We will use the virt-filesystems tool (which on my CentOS 8 system comes from the libguestfs-tools-c package):

$ virt-filesystems -a centos8-uefi.qcow2 --filesystems --long --uuids
Name      Type       VFS  Label           Size       Parent UUID
/dev/sda1 filesystem vfat MKFS_ESP        576716800  -      93C3-C214
/dev/sda3 filesystem ext4 cloudimg-rootfs 3293577216 -      3ef8f8c2-439f-4aad-86e1-6d2457364c24

Looking great! We can use both labels and UUIDs. Labels will probably be the same for any image created with diskimage-builder (I haven't verified this statement), UUIDs are more reliable within the same image.

Let us update our inject_files.json adding a new hello-world quality file and some parent directories to create:

[
  {
    "interface": "deploy",
    "step": "inject_files",
    "args": {
      "files": [
        {
          "path": "/etc/motd",
          "content": "SGVsbG8gSXJvbmljIFdvcmxkIQo="
        },
        {
          "path": "nonEFI/hello",
          "partition": "/dev/disk/by-uuid/93C3-C214",
          "content": "SGVsbG8gSXJvbmljIFdvcmxkIQo="
        }
      ]
    },
    "priority": 50
  }
]

After deploying and logging into the system, we see the file in place:

[centos@localhost ~]$ cat /boot/efi/nonEFI/hello
Hello Ironic World!

Node-specific content

Imagine you're using deploy templates, but still want the file content to be node-specific. How can we achieve that? Through passing a URL to content. Not only does it allow to fetch content remotely, it also supports simple Python formatting with node and ports parameters, for example:

• Fetch file based on UUID: http://host/{node[uuid]}.bin.

• Access a remote service with the first MAC: http://host/?mac={ports[0][address]}.

We will generate static files based on node names (which on a Bifrost testing environment look like testvm<N> where <N> is a number starting with 1):

$ find /httpboot/ -name testvm\* -print -exec cat {} \;
/httpboot/testvm1.txt
I am node 1
/httpboot/testvm2.txt
And I am node 2

Update the deploy steps again:

[
  {
    "interface": "deploy",
    "step": "inject_files",
    "args": {
      "files": [
        {
          "path": "/etc/motd",
          "content": "http://192.168.122.1:8080/{node[name]}.txt"
        }
      ]
    },
    "priority": 50
  }
]

Then create a deploy template and declare all nodes compatible with it:

$ baremetal deploy template create CUSTOM_INJECT_FILES --steps inject_files.json --max-width 100
+------------+-------------------------------------------------------------------------------------+
| Field      | Value                                                                               |
+------------+-------------------------------------------------------------------------------------+
| created_at | 2021-02-17T15:43:34.660443+00:00                                                    |
| extra      | {}                                                                                  |
| name       | CUSTOM_INJECT_FILES                                                                 |
| steps      | [{'interface': 'deploy', 'step': 'inject_files', 'args': {'files': [{'path':        |
|            | '/etc/motd', 'content': 'http://192.168.122.1:8080/{node[name]}.txt'}]},            |
|            | 'priority': 50}]                                                                    |
| updated_at | None                                                                                |
| uuid       | 3ebf8dac-896b-4633-b965-d6e2830ff5cc                                                |
+------------+-------------------------------------------------------------------------------------+
$ for node in $(baremetal node list -f value --fields uuid); do baremetal node add trait $node CUSTOM_INJECT_FILES; done
Added trait CUSTOM_INJECT_FILES
Added trait CUSTOM_INJECT_FILES

Now we can use metalsmith to pick any suitable node and deploy on it:

$ metalsmith deploy --resource-class baremetal --trait CUSTOM_INJECT_FILES \
      --image file:///httpboot/centos8.qcow2 --ssh-public-key ~/.ssh/id_ed25519.pub
+--------------------------------------+-----------+--------------------------------------+----------+--------+--------------+
| UUID                                 | Node Name | Allocation UUID                      | Hostname | State  | IP Addresses |
+--------------------------------------+-----------+--------------------------------------+----------+--------+--------------+
| 4e41df61-84b1-5856-bfb6-6b5f2cd3dd11 | testvm1   | f1be9ff3-965b-4500-bb7b-59673faba68a | testvm1  | ACTIVE |              |
+--------------------------------------+-----------+--------------------------------------+----------+--------+--------------+

As you see, this is node number 1, and as expected it greets us with:

I am node 1