Ruby code on Chef as a "ruby_block" not working

sparc86 · 11-06-2013, 06:58 AM

Hi LQ community,

I have very limited knowledge of the Ruby programming language, however, I need to implement on Chef something similar to "augeas" (which works with Puppet, but here I need a solution for Chef).

I got the example code below but it's not working and I am now for a few days trying to figure out what is wrong.

Basically I need to be able to select specific strings in a text file and modify these values. I could use sed but perhaps I can do it in a more elegant way using the ruby_block from Chef.

Please let me know what can be possibly wrong with the code below. Why is my /etc/hosts not being updated with new values?

Thanks for your help.

Follows my default.rb file:

Code:

ruby_block "edit etc hosts" do
  block do
    rc = Chef::Util::FileEdit.new("/etc/hosts")
    rc.search_file_replace_line(
      /^127\.0\.0\.1 localhost$/,
      "127.0.0.1 #{new_fqdn} #{new_hostname} localhost"
    )
    rc.write_file
  end
end

grail · 11-06-2013, 08:32 AM

Is this example something you have cobbled from an example someone has shown you?

I am not overly familiar with Chef but after a quick search I found the following:

Quote:

As soon as you wrap your code in ruby_block you cannot use ordinary recipe resource declaration anymore.

Which made me wonder if your reference to Chef::... was valid in this context?

Sorry if this is completely on the wrong path

sparc86 · 11-06-2013, 09:57 AM

Quote:

Is this example something you have cobbled from an example someone has shown you?

Yes, I got it from here: http://sysadvent.blogspot.de/2012/12...ow.html#item_2

Quote:

Which made me wonder if your reference to Chef::... was valid in this context?

Do you suggest that in the same default.rb file I cannot use chef code, even outside of the ruby_block function? Just in case, I have tried to comment the whole default.rb file, leaving ONLY the ruby_block function alone, but the problem persist.

grail · 11-06-2013, 10:08 AM

hmmm ... seems this is an added module via gems hence Chef is part of your Ruby installation

Hence you are using ruby code only inside the ruby_block.

I have only looked over a few examples, but the default.rb seems to be something that sets up the recipe where the task you have set seems to be more of something the recipe would do
after being setup (Could be completely off here btw)

Sorry I can't be of more help as again I am not familiar enough with Chef's workings

sparc86 · 11-06-2013, 10:16 AM

Quote:

Sorry I can't be of more help as again I am not familiar enough with Chef's workings

Chef is a BEAST, they manage to make it even more complicated than Puppet. Configuration Management rocks and I personally like bcfg2 but where I work today we need Chef.

Anyway, thanks for your help, let's wait, perhaps some ruby/chef hacker may appear sooner or later.

grail · 11-07-2013, 01:46 AM

Well I do know Ruby

Things to consider:

1. Does your /etc/hosts have the line exactly as the regex looking for it?

Code:

/^127\.0\.0\.1 localhost$/

So line starts with 127 and there is only a single space (not tab) between last 1 and localhost and there is no white space after localhost

2. #{new_fqdn} #{new_hostname} - these are variable calls so obviously you need to have already set these somewhere else

See if that helps a bit

sparc86 · 11-07-2013, 02:25 AM

I have tried to change the strings to just 127.0.0.1 and it is not working.

After I run chef-solo, I get the following error:

Quote:

NoMethodError
-------------
undefined method `chef' for Chef::Resource::RubyBlock

Thanks for your help, I really appreciate it.

grail · 11-07-2013, 06:57 AM

Well silly question but you do have the Chef gem installed?

sparc86 · 11-07-2013, 09:23 AM

I think so.

Quote:

[root@chef recipes]# whereis gem
gem: /usr/bin/gem

is there any other test I could make in order to verify for libraries or so?

grail · 11-08-2013, 09:19 AM

Try:

Code:

$ gem list

$ is my prompt

sparc86 · 11-08-2013, 09:27 AM

Quote:

[root@chef recipes]# gem list

*** LOCAL GEMS ***

chef (11.6.2)
erubis (2.7.0)
highline (1.6.20)
ipaddress (0.8.0)
json (1.7.7)
mime-types (1.25)
mixlib-authentication (1.3.0)
mixlib-cli (1.3.0)
mixlib-config (1.1.2)
mixlib-log (1.6.0)
mixlib-shellout (1.2.0)
net-ssh (2.7.0)
net-ssh-gateway (1.2.0)
net-ssh-multi (1.1)
ohai (6.18.0)
rest-client (1.6.7)
systemu (2.5.2)
yajl-ruby (1.1.0)
[root@chef recipes]#

Any suggestions?

Thanks!

grail · 11-08-2013, 10:06 AM

Sorry ... no ... will need to wait for a Chef person

I mean the error makes sense to me but we do not call 'chef' in lower case in this code ... which to me would point to the error being elsewhere??
Maybe there are other files you have edited ... or not edited?

sparc86 · 11-11-2013, 03:10 AM

Ok, perhaps it would be a good idea if I copy you here all the relevant config files.

/etc/chef/solo.rb:

Quote:

file_cache_path "/var/chef"
cookbook_path "/var/chef/cookbooks"
json_attribs "http://127.0.0.1/node.json"
recipe_url "http://127.0.0.1/chef-solo.tar.gz"

Here I understand it is non-sense to run such code in a cron recipe but it is just for testing purposes.
/var/chef/cookbooks/cron/recipes/default.rb:

Quote:

ruby_block "edit etc hosts" do
require 'chef/util/file_edit'
block do
rc = Chef::Util::FileEdit.new("/etc/hosts")
rc.search_file_replace_line(
/^127\.0\.0\.1 localhost/,
"127.0.0.1 #{chef.hostname.local} #{hostname} localhost"
)
rc.write_file
end
end

The following line deserves a brief explation. Here I have setup a local webserver on /root/ and therefore chef-solo can read the "/etc/chef/solo.rb" file and can call for node.json and other files. In the future we plan to use a dedicated webserver but at the moment it is ok to keep it local for testing purposes.
/root/node.json:

Quote:

{
"run_list": [ "recipe[helloworld]", "recipe[crondemo::remove]", "recipe[ntp]", "recipe[cron]", "recipe[umask]", "recipe[rsync]", "recipe[sudo_env]", "recipe[permissions]" ]
}

Overall, do you see anything potentially wrong?

grail · 11-11-2013, 06:33 AM

Well only the obvious question comes to me, does the default recipe need to be in the run_list or is it assumed if present it is always executed?

Note: To save your formatting here use 'code' instead of 'quote' tags

sparc86 · 11-11-2013, 06:49 AM

Yes, it must be declared in the run_list, which is the case indeed, as the config being used for testing is the cron recipe.

Thanks for the tip about the CODE tags

So, any thoughts?