How can I edit a chef attribute of an ec2 node using knife

Question

I want to edit ec2 node's node_data using a knife node command.
I can manually do it by using below command.
knife node edit NODE_NAME
It will generate a json which I need to edit.

"name": "NODE-1",
  3   "chef_environment": "test",
  4   "normal": {
  5     "node_data": {
  6       "version": "23690ecc9c572e47db242bfad1296388f91da1e9",
  7       "depot_path": "https://s3.amazonaws.com/builds/",
  8       "source_repo": "softwares/"
  9     },
 10     "tags": [
 11 
 12     ]
 13   },
 14   "run_list": [
 15     "role[my-role]"
 16   ]
 17 }

I want to edit node_data in that json.
If I had to edit run_list the there is a command for that
knife node run_list add node 'role[ROLE_NAME]'
I need something similar to this command.

Answer 1

It sounds like you want a scriptable/non-interactive way to set an attribute of a given node. You can use knife exec for this.

For your given example, suppose you want to get and set the value of source_repo in node_data for "NODE-1". You could achieve this by running:

knife exec -E "nodes.find(:name => 'NODE-1') { |node| node['node_data']['source_repo'] = '/new/path/softwares/'; node.save; }"

Note the node.save at the end: this will make the chef server save your changes. If this is missing in the command, then it's a temporary change that is not saved on the chef server.

To confirm that the attribute has indeed changed on the chef server, you can get the current value like this:

knife exec -E "nodes.find(:name => 'NODE-1') { |node| puts node['node_data']['source_repo'] }"

You should see: /new/path/softwares/ as the output of the above command.

By the way, note that node['node_data']['source_repo'] is equivalent to (and can be replaced with) node.node_data.source_repo