From: Tony Arcieri <tony.arcieri@...>
Date: 2010-10-19T09:01:25+09:00
Subject: Re: su {block of code.}

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On Mon, Oct 18, 2010 at 5:20 PM, Guido De Rosa <guidoderosa@gmail.com>wrote:

>  o.instance_eval do
>    ::File.open('/TEST', 'w'){|f| f.puts 'hello'}
>  end
>
> I keep getting a Permission Denied error (Errno::EACCES)
>
> And if I change '/TEST' into '/tmp/TEST', It's clearly seen that the
> file has been created by the normal user, not by root.


Well yes, this isn't going to work, because you're talking to the File
singleton object here, not to the main object over DRb.

I guess my question is what exactly are you trying to accomplish? Do you
want a small DSL of commands to work with files as root, or are you
expecting everything to be executed in the context of the setuid root VM?

If it's the former, try this:

include FileUtils
cp "somefile", "anotherfile"

That should operate as expected. Beyond that, you would need to use
ParseTree or ripper to extract the Ruby code you want executed on the remote
VM or something like that, but then you need to ensure that all the
classes/objects it's using are actually loaded on the new VM.

For practicality's sake I'd suggest exposing a small DSL for doing what you
want to do as root. FileUtils provides everything I'd think you need, but
perhaps you have a use case I'm not envisioning.

-- 
Tony Arcieri
Medioh! A Kudelski Brand

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