CHEF - ArgumentError: could not find a temporary directory

When running chef-client as non root user, you may encounter the following error:

==============================
  Error Syncing Cookbooks:
  =============================
  Unexpected Error:
  -----------------
  ArgumentError: could not find a temporary directory
 
  Platform:
  ---------
  x86_64-linux

In the stacktrace, the error shows up as:
ArgumentError: could not find a temporary directory
/opt/chef/embedded/lib/ruby/2.1.0/tmpdir.rb:34:in `tmpdir'
/opt/chef/embedded/lib/ruby/2.1.0/tmpdir.rb:105:in `tmpdir'
/opt/chef/embedded/lib/ruby/2.1.0/tmpdir.rb:137:in `create'
/opt/chef/embedded/lib/ruby/2.1.0/tempfile.rb:136:in `initialize'
/opt/chef/embedded/lib/ruby/2.1.0/tempfile.rb:320:in `new'
/opt/chef/embedded/lib/ruby/2.1.0/tempfile.rb:320:in `open'

Solution:
This is not a CHEF issue rather a ruby one. Newer versions of ruby do not allow any directory to be used as a temporary directory that has (777) permissions set on it unless setuid of 1 is set on the directory too. As root user do the following:

chmod 1777 /tmp
ls -ld /tmp  drwxrwxrwt. /tmp

notice the "t" in the output.

CHEF - Running chef-client as non-root user

Chef works best when run as root user but there are scenarios when you would want to run a chef-client as non root user. To do that, do the following steps:

Assumption:
It is assumed that you already have bootstrapped the node and/or installed the chef-client.  Also, it assumes that you have access to the client.pem key needed to talk to the CHEF server. For this example, we'll assume the non root user is "oracle".

Step 1:
As root, copy the entire content of /etc/chef folder to "oracle" user's home directory and change permissions.
cp -rf  /etc/chef /home/oracle/.chef
chown -R oracle:oinstall /home/oracle/.chef

Step 2:
Open the /home/oracle/.che/client.rb file and add the following lines:
cache_path "/home/oracle/.chef"
client_key "/home/oracle/.chef/client.pem"
 
If you don't specify cache_path, you will get the error:
Unable to access cache at /var/chef. Switching cache to /home/oracle/.chef
whenever you run the chef-client as oracle user.

If you don't specify the client_key location, chef-client will look at /etc/chef/client.pem file, if the file is not readable (by default it won't), the client will error out with

Private Key Not Found:
----------------------
Your private key could not be loaded. If the key file exists, ensure that it is
readable by chef-client.

Relevant Config Settings:
-------------------------
validation_key "/etc/chef/validation.pem"

Step 3:
Now, run the chef-client with the following arguments:
chef-client -o recipe[] -c /home/oracle/.chef/client.rb