我对厨师很陌生，正在努力学习。我已经在我的系统上安装了 chef-client，在我的 chef-repo 的 chef 目录中复制了 .pem 文件和knife.rb 文件，现在我正在尝试访问knife，但我收到了以下错误。谁能帮我吗 ？
prateek@prateek-desktop:~/mygit/chef-repo/chef$ knife client list -VV
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/mixin/path_sanity.rb:26:in `enforce_path_sanity': undefined method `split' for nil:NilClass (NoMethodError)
from /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/knife.rb:465:in `run_with_pretty_exceptions'
from /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/knife.rb:173:in `run'
from /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application/knife.rb:123:in `run'
from /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/bin/knife:25:in `<top (required)>'
from /usr/bin/knife:23:in `load'
from /usr/bin/knife:23:in `<main>'