Iterate over array to mount NFS directories

[Forrie]

I have many systems that require NFS mounts for production.  Rather than have one entry of file{} and mount{} per NFS import, in a *.pp file, I'd rather set up and iterate over an array.   Looking at the docs, I'm not quite sure how to do this properly.  We have three groups for which I would need this (production, development, test) that each have their own NFS mounts.

here's what I would use:

$server = "server.name.com"

$prefix = "/some/nfs/root"

# array

production = [ 

              "dir1", 

              "dir2", 

              "dir3", 

              "dir4", 

] # etc etc

Then issue a command to iterate and manage those NFS mounts.

Since these change from time-to-time, and require some pruning... I will be left with "unmanaged" resources (ie: directory mount points) scattered around that I will need to clean up.  I read through some tickets for feature requests and got lost in where this is going -- however, to keep the place neat and clean, I'd like to unmanage the mount points and the fstab entries after.   The idea of manually doing this from system to system isn't good.

I'm still new-ish to puppet, so any pointers would be appreciated.

Thanks.

[Luke Bigum]

Hi Forrie,

With regards to your iteration question, you would need to use a defined
type, something like this (untested):

define nfs_mount ( $server, $prefix, $state = "mounted" ) {
$mount_point = "${prefix}/${name}"

#If the state is "unmounted" the mount point 'File' is removed
file { $mount_point:
ensure => $state ? {
"unmounted" => absent,
"absent" => absent,
default => present,
}
}

mount { $mount_point:
ensure => $state,
device => "{$server}:${mount_point}",
}
}

nfs_mount { $production: server => $server, prefix => $prefix}

See the documentation for the Mount type in Puppet and it's ensure
parameter for possible values for $state in the define above - it's
possible to have entries in /etc/fstab but not actually mounted, which
should satisfy your two stage cleanup, or you can just set $state to
'absent' straight away and clean up the both NFS mount and mount point.
This means you need to maintain two arrays: one of active mount points
and one of decomissioned mounts, however you probably don't need to keep
the decomissioned mounts around for ever, once every server has cleaned
themselves up they can be removed from the manifest.

http://docs.puppetlabs.com/references/latest/type.html#mount

Hope that helps,

-Luke

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[Forrie]

Thank you for your reply :)

The head of the code would need something like this:

$server = "nfs-server.domain.com"

$prefix = "/our/prefix"

# Arrays to iterate over, which would be a little longer than this

$proddirs = [ "201201", "201202", "201203" ]

$testdirs = [ "201201", "201202", "201203" ]

$devdirs  = [ "201201", "201202", "201203" ]

$nfsopts  = "tcp,hard,intr,rw,bg"

By "iterate" I meant to work through a specific array, such as above.   

Reading through the Mount part of the docs, I don't believe that "absent" will remove the actual directory point, it says:

"Set it to absent to unmount (if necessary) and remove the filesystem from the fstab"

So I would handle that by running another iteration over an array for each section that would have a routine to make sure it's "absent" and then also rmdir the entry in the filesystem.

I'm not understanding where the below is iterating or over where... as $name would need to be defined somehow.

Thanks!

[Luke Bigum]

Hi Forrie,

My example below uses a defined type (http://docs.puppetlabs.com/puppet/2.7/reference/lang_defined_types.html) to group two related resources together, in this case the File resource for the mount point and the Mount resource for the NFS mount itself.

To answer your first question, no, "ensure=>absent" in a Mount resource will not remove the mount point directory. That is why I've wrapped the File and Mount point in a define, so you can use one definition of nfs_mount to control both mount point and NFS mount together, as in your scenario they are two closely related resources.

You will notice the $state parameter of my defined type is used in two places: for the 'ensure' parameter of the Mount (described in the docs for the Mount type) and the 'ensure' parameter of the File. Since the ensure parameter of the Mount type takes different arguments to the File type, I use a selector to transform the Mount point's state into a state I can use in a File resource. The selector (ensure => $state ? {...} ) basically says this:

"If $state is unmounted, the File is absent"
"If $state is absent, the File is absent"
"If $state is anything else, the File is directory"

file { $mount_point:
         ensure => $state ? {
             "unmounted" => absent,
             "absent" => absent,

             default => directory,
         }
}

I just noticed a bug in my original post, it should be "default => directory" to create a directory, not a file :-)

http://docs.puppetlabs.com/puppet/2.7/reference/lang_conditional.html#selectors

As for the second question about the iteration, the iteration works the same way for a defined type as it does for any core Puppet type (File, Mount, Service, etc). Although it's not really a procedural "loop", it's just a short hand way of writing out a set of resource definitions with exactly the same parameters, but the effect is the same.

So doing these :

file { $proddirs: ... }
mount { $proddirs: ... }

is the same as this:

nfs_mount { $proddirs: ... }

Now the $name parameter or is the namevar of the defined type (http://docs.puppetlabs.com/puppet/2.7/reference/lang_resources.html#namenamevar). It's the unique name of the resource, works the same as other Puppet Types, in the examples below it is the strings "apache" and "/mnt/server/woof":

package { "apache": }
nfs_mount { "/mnt/server/woof/": }

You can use $name inside a defined type just like any other variable / parameter.

So in an example use of my defined type, this definition:

nfs_mount{ "201201":
  state  => "mounted",
  server => "nfs-server.domain.com",
  prefix => "/our/prefix",
}

Will result in the following standard Puppet resources:

file { "/our/prefix/201201":
  ensure => "directory",
}
mount { "/our/prefix/201201":
  ensure => "mounted",
  device => "nfs-server.domain.com:/our/prefix/201201",
}

Hopefully that explains the use of the defined type in more detail. If you have any more questions, please ask :-)

-Luke

             default => directory,

To view this discussion on the web visit https://groups.google.com/d/msg/puppet-users/-/wCGS0RWvZFwJ.

[Luke Bigum]

Hi Forrie,

Good to see you are almost there! As you've discovered the "looping" in Puppet isn't *really* looping, it's just a shorthand way of creating multiple resources. However, by combining that with a Defined Type, you can effectively reference the same array element multiple times using $name in the define - as we do with the File and Mount resources - and you achieve an approximation of a loop.

Also remember there was a bug in my original post, the File resource needs "default => directory" to create a directory, not "present", as that would create a file instead, but it looks like you've figured that out anyway.

Unfortunately there is no way to recursively create directories in Puppet. You will need to manage the File[/dce/prod/] directory outside of the nfs_mount resources. Why? If you have more than one Prod nfs_mount, you will get duplicate definitions when you try create /dce/prod/ inside the nfs_mount define.

In your example below you have a class called prod-nfs-mounts. Inside this class you could have a file { "/dce/prod": ensure => directory } resource to ensure the parent directory is created.

One mor bug: the Mount resource should have a dependency on the File resource - you can't mount before the mount point is there. Add a parameter 'require => File[$mount_point]' to the mount resource in the define.

Also just so you know, older versions of Puppet don't like dashes (-) in class and variable names, so I would recommend you use underscores where possible.

-Luke

On 26/09/12 21:59, Forrest Aldrich wrote:

I did some tinkering around and came up with something that partially works.  The one problem I ran into was this:

Sep 26 16:53:55 test-fms puppet-agent[11974]: (/Stage[main]/Prod-nfs-mounts/Prod-nfs-mounts::Nfs_mount[201202]/File[/dce/prod/201202]/ensure) change from absent to present failed: Could not set 'present on ensure: No such file or directory - /dce/prod/201202 at /etc/puppet/manifests/classes/prod-nfs-mounts.pp:19

I changed the default for the "ensure" value to be "directory" and that didn't help, but this is strange:

Sep 26 16:56:50 test-fms puppet-agent[12776]: (/Stage[main]/Prod-nfs-mounts/Prod-nfs-mounts::Nfs_mount[201202]/File[/dce/prod/201202]/ensure) change from absent to directory failed: Cannot create /dce/prod/201202; parent directory /dce/prod does not exist
Sep 26 16:56:51 test-fms puppet-agent[12776]: Finished catalog run in 6.08 seconds

I can't recall, but there is a way to ensure the directory mount point is recursively present before a mount is attempted.

It should not be trying to create a local directory, but mounting from the remote host.    I think I'm almost there, but here's the test class I have thus far:



$production = [ "201201", "201202", "201203" ]
$server     = "de-prod-nas.ourdom.com"
$prefix     = "/dce/prod"
$nfsopts    = "tcp,hard,intr,rw,bg"

class prod-nfs-mounts {

        define nfs_mount ( $server, $prefix, $state = "mounted" ) {
  
                        $mount_point = "${prefix}/${name}"

                    # If the state is "unmounted" the mount point 'File' needs to be removed somehow, after

                    file { $mount_point:
                        ensure => $state ? {
                            "unmounted" => absent,
                            "absent"    => absent,

                            default     => present,

                        }
                    }

                    mount { $mount_point:
                        ensure  => $state,

                        atboot  => true,
                        options => "$nfsopts",

                        device  => "{$server}:${mount_point}",
                    }
        }

        nfs_mount { $production: server => $server, prefix => $prefix }
}

Thanks again ! :-)