Java – Chef Java Cookbook – JDK Upgrades

I'm not so keen on the total_memory idea it's somewhat of an indirect quantity. Maybe it makes more sense in the context of whatever the magical daemon is though.

For tunable attributes like total memory, I pretty much would do as you have laid out in the question by adding a sensible default value to attributes/default.rb (cuts down on support questions when someone forgets to explicitly set a value) and override with environment, role or node-specific values where necessary.

It's possible to do arithmetic inside the ERB file like this:

memory = <%= (node['memory']['total'][0..-3].to_i / 1024) * 
             node['magical-daemon']['memory'] %>

Ohai makes available the statistics from free(1) which includes the total memory in kB. node['memory']['total'] = '12312432kB' on my workstation.

I also try and use attributes with the lowest priority as much as possible, i.e prefer default over normal attributes, and normal attributes over override attributes. So,

• choose a sensible recipe default where possible
• use a default environment attribute (you use an override attribute in the example)
• use a role attribute for groups of nodes (again you use an override attribute)
• and finally default node attribute

See the attribute precedence link in the Chef wiki) for the order in which attributes override each other.

Using the lowest precedence default attributes where possible allows you to set the attribute value depending on the environment, role and node, but frees up the upper levels of precedence when you need to do something tricky.

After you unpack the linux bin, You have to let system know.

alternatives --install /usr/bin/java java /path/to/your/java 10

then you can config it with

alternatives --config java