Puppet users - Jan 2011 - Create a file only under certain conditions

Is there a way to create a file only under certain conditions?

I would like to check if a certain device exists and the config file is 
still missing. If the file ist missing, create the file and update the 
initramdisk. (This device exists only on our notebooks, otherwise it is a 
desktop and nothing should be done)

This is our first try:

class hibernate {

         notice("hibernate")

         exec { "echo":
                 alias       => "echo",
#               onlyif      => "test -b /dev/mapper/swap_crypt -a ! -f
/etc/initramfs-tools/conf.d/resume" ,
#               onlyif      => "true" ,
                 onlyif      => "false" ,
         }

# should not be created as Exec["echo"] is "false"!
# ... but "resume" is still created
         file { "resume":
                 name   => "/etc/initramfs-tools/conf.d/resume",
                 source => "puppet:///modules/hibernate/resume",
                 mode   => 644,
                 require => Exec["echo"],
         }

# should not be execute as Exec["echo"] is "false"!
# ... but is executed because "resume" had been created
         exec { "update-initramfs":
                 name => "update-initramfs -u",
                 refreshonly => true,
                 subscribe   => File["resume"],
         }


}

Even Exec["echo"] is not beeing executed, the file "resume"
will be
created and "update-initramfs" is executed.


The workaround is to avoid the file-type an simple use an exec with an 
"echo .. > file" in it.

class hibernate {

         exec { "echo RESUME=/dev/mapper/swap_crypt >
/etc/initramfs-tools/conf.d/resume":
                 alias       => "echo",
                 onlyif      => "test -b /dev/mapper/swap_crypt -a ! -f
/etc/initramfs-tools/conf.d/resume" ,
         }

# if "onlyif" is successful, then Exec["update-initramfs"]
is triggerd
         exec { "update-initramfs":
                 name => "update-initramfs -u",
                 refreshonly => true,
                 subscribe   => Exec["echo"],
         }

}


Is there any way to use something like "refreshonly" also for File?

Patrick


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On Jan 28, 2011 6:12 AM, "Patrick Cervicek" <
patrick@googlealtert.spamtrap.fht-esslingen.de>
wrote:
>
> Is there a way to create a file only under certain conditions?
Totally, and we did it routinely. The process is perhaps not quite as simple
as you might expect though:

You need to write a custom fact to run on the client, and which reports the
presence or absence of the device to the server. Your manifest can then use
that fact to determine what other actions to take.

Custom facts in modules are pretty trivial to write. :)

Regards,
    Daniel
-- 
Puppet Labs Developer –http://puppetlabs.com
Daniel Pittman <daniel@puppetlabs.com>
Contact me via gtalk, email, or phone: +1 (877) 575-9775
Sent from a mobile device. Please forgive me if this is briefer than usual.

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On Jan 28, 8:12 am, Patrick Cervicek
<patr...@googlealtert.spamtrap.fht-esslingen.de>
wrote:
> Is there a way to create a file only under certain conditions?
What Daniel said.

For the record, though:
> class hibernate {
>
>          notice("hibernate")
>
>          exec { "echo":
>                  alias       => "echo",
> #               onlyif      => "test -b /dev/mapper/swap_crypt -a !
-f /etc/initramfs-tools/conf.d/resume" ,
> #               onlyif      => "true" ,
>                  onlyif      => "false" ,
>          }
>
> # should not be created as Exec["echo"] is "false"!
> # ... but "resume" is still created
>          file { "resume":
>                  name   =>
"/etc/initramfs-tools/conf.d/resume",
>                  source =>
"puppet:///modules/hibernate/resume",
>                  mode   => 644,
>                  require => Exec["echo"],
>          }
I think you have a misconception here about the semantics of onlyif.
OnlyIf does not cause an Exec to fail when its condition is false.
Instead, it causes the Exec to *succeed* without actually running the
command.  This is intentional, with the express purpose that resources
that depend on an Exec are still applied when the Exec is short-
circuited.

More generally, the Exec resource is not intended for the purpose to
which you are trying to put it.  You could probably force it to serve
by making your onlyif command be the main command, but that''s ugly,
and it will report errors on most runs.  Instead, the puppetmaster
should decide, based on the facts presented to it, what resources
should be applied on each node.


John

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