RE: How to copy, alert and shellcommand

[Wheeler, John]

> Im new to cfengine, can you explain a bit furtherwhat the example does
> part
> by part?
> %control:

The control[1] section defines what cfagent will do when run. In this
case we have two directives. The first one (arguable the most important)
actionsequence is as the name implies a sequence of actions that the
agent will execute in the order they appear in the list. In this case
the action of "copy"[3] followed by "shellcommands"[4] will be executed.
This definition in itself does nothing; you must define in the
corresponding sections what syntactically correct "action" to take.

[1] http://www.cfengine.org/docs/cfengine-Reference.html#control
[2] http://www.cfengine.org/docs/cfengine-Reference.html#actionsequence
[3] http://www.cfengine.org/docs/cfengine-Reference.html#copy
[4] http://www.cfengine.org/docs/cfengine-Reference.html#shellcommands


> %
> % actionsequence = ( copy shellcommands )
> %
> % AddInstallables = ( blah )

The second directive AddInstallable[5] is intended to help the cfagent
parser optimize "code" included by the activation of the class "blah"[6]
that may otherwise be excluded if the class were not activated[7]. I'll
explain this further when the class is used.

[5]http://www.cfengine.org/docs/cfengine-Reference.html#addinstallable
[6]My personal favorite "example" variable.
[7]For reasons beyond comprehension, sorry mark.

> %
> %copy:

Ahhhh... our first "action" section, copy. This section says "from"
which is intended to indicate the source path of the file to copy. Say
you want to copy /etc/hosts from somewhere (locally or remotely). The
copy section would look like

copy:
    /etc/hosts
        dest=/etc/hosts

Also note the define statement. This is where our mysterious "blah"
class shows up. From reading the documentation one would come to realize
that this class will be defined if and only if the file is copied. 

> %
> %  from dest=to define=blah
> %
> %shellcommands:


This is where we define the shellcommands. Note that even though the
order of these sections (shellcommands and copy) happens to follow the
order in the action sequence, the order is irrelevant. The action
sequence dictates the order of events.

Notice here that the bogus shellcommand (fully pathed!) /bin/runme will
not be run unless the blah class is set.  This is why the addinstallable
is important, because the class blah is a dynamic class, activated by
another action, the parser would otherwise ignore this section of the
shellcommands had we not place this class in the addinstallable
directive.

> %
> %  blah::
> %
> %     "/bin/runme balbla"
> %
> %alerts:

I honestly can't speak intelligently about alerts, I just don't use
them... yet. Basically, using the dynamic class "blah" again, the
message in quotes below will be puked to the screen or arrive in an
email (assuming you've set the sysadmin[8]) if and only if the file in
question is copied.

[8] http://www.cfengine.org/docs/cfengine-Reference.html#sysadm


> %
> %  blah::
> %
> %    "I was copied"
> %
> %

My best advice is to spend a bit of time reading both the reference[9]
and the tutorial[10] thoroughly. These are invaluable sources of
information. Also, google is your friend. Finally, setup a test
environment to perform simple examples and convince yourself of its
functionality.


[9]http://www.cfengine.org/docs/cfengine-Reference.html
[10]http://www.cfengine.org/docs/cfengine-Tutorial.html