add blog entry that describes how to recursively transfer files

Signed-off-by: Nico Schottelius <nico@brief.schottelius.org>

blog/cdist-transfer-files-recursively.mdwn

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+[[!meta title="Cdist: How to copy a folder recursively"]]
+
+## Introduction
+
+This article describes one solution to transfer a folder
+and all of its contents recursively with [[cdist homepage|software/cdist]]
+to target hosts. I am motivated to do so, because I want to have one
+central place to configure the tftproot that I may use on a variety
+of KVM hosts.
+
+Traditionally, it is not an easy job to handle recursive transfer correctly
+and efficiently in a configuration management system. Using a sophisticated
+tool like [rsync](http://rsync.samba.org/) or
+[unison](http://www.cis.upenn.edu/~bcpierce/unison/) makes life way easier.
+
+## Copying the files recursively
+
+Cdist knows about the types **\_\_file** and **\_\_directory** for
+file transfer and directory management.
+The type **\_\_nico\_tftp\_root**,
+which can be found in the
+[cdist-nico git repository](http://git.schottelius.org/?p=cdist-nico)
+(below **cdist/conf/type**) recursively copies all files it has to
+the folder **/home/service/tftp**. Only when a file is changed, it
+is transferred again (the **\_\_file** type takes care of this).
+
+## The manifest
+
+In cdist, a manifest of a type defines, which other types to use.
+A manifest file is essentially shell code, that can call other
+cdist types.
+
+To accomplish the task, first of all the base directory is created
+on the remote site:
+
+    basedir=/home/services/tftp
+    __directory "$basedir" --mode 0755
+    
+Afterwards, I change into the source directory
+and find all files. Cdist exports the
+variable "__type" to access the folder in which the type is stored.
+
+    cd "$__type/files"
+    
+    for file in $(find . | sed 's;./;;' | grep -v '^\.$' ); do
+
+The grep command is needed, to skip the current directory, that is returned
+by find.
+
+Now, for every file I determine the remote file name. Furthermore
+dependencies to the required directories are setup: 
+You can **require** another type to be run before a type, by setting
+up the **require** environment variable (this will be changed in cdist
+2.1. and replaced in 2.2, but there is still some time until this is released).
+
+The remote name is constructed by this line:
+
+        name="$basedir/$file"
+    
+And the requirement is setup using this line:
+
+        # Require the previous directory in the path
+        export require="__directory/${name%/*}"
+
+The shell (!) knows about string manipulation: ${variablename%/*} replaces
+the shortest matching suffix that equals "/*". And thus the previous
+statement removes the last part of the path (also known as dirname).
+
+If the file found by find is a file, we call the \_\_file type,
+if the file is actually a directory, the \_\_directory type is called:
+
+        if [ -d "$file" ]; then
+            __directory "$name" --mode 0755
+        else
+            __file "$basedir/$file" --source "$__type/files/$file" \
+                --mode 0644
+        fi
+    done
+
+And that's it - a full recursive copy with just a bunch of lines.
+
+## Further Reading
+
+* [[cdist|software/cdist]]
+* [cdist-nico git repository](http://git.schottelius.org/?p=cdist-nico)
+* [manifest of __nico_tftp_root](http://git.schottelius.org/?p=cdist-nico;a=blob;f=cdist/conf/type/__nico_tftp_root/manifest;h=b312210d878b30e5871751d62cea14172f63c756;hb=HEAD)
+
+[[!tag cdist config unix]]