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Get to know a gem: Ghost

Posted by Mon, 12 Jan 2009 06:18:00 GMT

In my last post, Subdomain accounts with Ruby on Rails explaind, I mentioned that you’d need to modify your /etc/hosts file to use custom subdomains for development/testing. Apparently, there is a much better way to handle this that I was introduced to by Nathan de Vries. Nathan suggests using a gem that I hadn’t heard of before that bares the name of Ghost (view project on github).

Ghost describes itself as…

“A gem that allows you to create, list, and modify local hostnames in 10.5 with ease…”—

If you’ve ever had to modify your /etc/hosts file for anything local, I highly encourage you to check out this shiny gem.

Installing Ghost

Like most gems, you can just install Ghost with the following command.

~ : sudo gem install ghost
Successfully installed ghost-0.1.2-universal-darwin-9
1 gem installed
Installing ri documentation for ghost-0.1.2-universal-darwin-9...
Installing RDoc documentation for ghost-0.1.2-universal-darwin-9...

Okay, now that Ghost is installed, let’s see what we can do with it.

Using Ghost for local domains/subdomains

Ghost is fairly straight forward. It’s essentially a friendly wrapper for dscl, which is the Directory Service command line utility for Mac OS X. I’ve never played with that directly, but it seems that with Ghost… I shouldn’t need to. :-)

With Ghost, you can add, modify, and delete entries in the Directory Service by issuing any of the following commands. Let’s start out by running ghost to see what we have here.

 ~ : ghost
USAGE: ghost add <hostname> [<ip=>]
       ghost modify <hostname> <ip>
       ghost delete <hostname>
       ghost list
       ghost empty

Okay, let’s see if there is anything already listed.

   ~ : ghost list
  Listing 0 host(s):

Nope. Let’s test this out. First, we’ll try to ping a domain name that we hope doesn’t exist.

   ~ : ping bigbrown.cow
  ping: cannot resolve bigbrown.cow: Unknown host  

Alright, now we’ll add bigbrown.cow with ghost.

   ~ : ghost add bigbrown.cow
    [Adding] bigbrown.cow ->

As you can see, it required root credentials to do this as it’s system-wide. Let’s now see if we can talk to bigbrown.cow.

   ~ : ping bigbrown.cow     
  PING bigbrown.cow ( 56 data bytes
  64 bytes from icmp_seq=0 ttl=64 time=0.047 ms
  64 bytes from icmp_seq=1 ttl=64 time=0.035 ms
  --- bigbrown.cow ping statistics ---
  2 packets transmitted, 2 packets received, 0% packet loss
  round-trip min/avg/max/stddev = 0.035/0.041/0.047/0.006 ms

Excellent! If we run ghost list again, we should see this record.

~ : ghost list
Listing 1 host(s):
  bigbrown.cow ->

We can modify the record to a non-localhost IP as well with ghost modify.

   ~ : ghost modify bigbrown.cow
    [Modifying] bigbrown.cow ->
   ~ : ghost list
  Listing 1 host(s):
    bigbrown.cow ->  

I’ll let you play with it yourself as there isn’t much to it. This is a great little addition to my development environment. Thanks to Nathan for pointing it out and to Bodaniel Jeanes for creating this useful gem.

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