Puppet users - Oct 2008 - puppet, facter and using non-scalar values

Hello all,

I''ve been using puppet for a while now and have an issue I''ve
not
seen clearly answered.  One of the issues I want to address in puppet
is to manage LVM, the volume groups and logical volumes on a series
of servers.

Starting from a small base configuration I would like to configure the
logical volumes on the server.

However this doesn''t seem to be a thing that puppet knows about
directly.
My first thought is to create some custom facts which store the volume
group names and within each volume group the logical volumes. This is
not ideally stored as a couple of scalar values.

So how should I store this? Facter would seem to be the best thing to
adjust adding some custom facts but from what I can see all facter facts
are single scalar values.

So am I approaching the problem incorrectly? My initial thought is
that I''d like to populate some sort of variable volume_group_info as a
hash of hashes, the first hash being indexed on the volume group names
and the second on the logical volume group names in each volume group.

Still being new to ruby I''m trying to work out how to do this straight
in ruby but I''m sure this can be done, and if so my question would by
how to translate this into puppet code.

I''m initally looking at doing something like:

-- snip --
vol_groups = Hash.new

puts vol_groups.to_s

if FileTest.exists?("/usr/sbin/lvs")
        %x{/usr/sbin/lvs --noheadings 2>/dev/null}.split("\n").each
do |line|
                if line =~ /\s+(\S+)\s+(\S+)/
                        puts "match vg: " + $2 + ", lv: " +
$1
                        lvname = $1
                        vgname = $2

			# now fill lvname into vol_groups by vgname...
                end
        end
end
-- snip --

Can anyone comment on this idea?

Simon

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On Oct 10, 2008, at 11:56 AM, Simon J Mudd wrote:
>
> Hello all,
>
> I''ve been using puppet for a while now and have an issue
I''ve not
> seen clearly answered.  One of the issues I want to address in puppet
> is to manage LVM, the volume groups and logical volumes on a series
> of servers.
>
> Starting from a small base configuration I would like to configure the
> logical volumes on the server.
>
> However this doesn''t seem to be a thing that puppet knows about  
> directly.
> My first thought is to create some custom facts which store the volume
> group names and within each volume group the logical volumes. This is
> not ideally stored as a couple of scalar values.
What are you going to be doing with the facts?  Wouldn''t you want to  
just declaratively manage the whole set of groups and volumes and such?

It''s not like you can iterate over the groups in Puppet or anything.
>
> So how should I store this? Facter would seem to be the best thing to
> adjust adding some custom facts but from what I can see all facter  
> facts
> are single scalar values.
>
> So am I approaching the problem incorrectly? My initial thought is
> that I''d like to populate some sort of variable volume_group_info
as a
> hash of hashes, the first hash being indexed on the volume group names
> and the second on the logical volume group names in each volume group.
The problem is that Puppet isn''t really set up to use this hash of  
hashes to make resources, and really, what''s the value of doing so  
anyway, since you''d just be telling Puppet to manage what it''s
already
discovered, right?

-- 
Due to circumstances beyond your control, you are master of your fate
and captain of your soul.
---------------------------------------------------------------------
Luke Kanies | http://reductivelabs.com | http://madstop.com


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Hi Luke,

Sorry for not replying earlier. I missed your reply.

On Oct 13, 2008, at 5:05 pm Luke Kanies wrote:
> What are you going to be doing with the facts?  Wouldn''t you want
to
> just declaratively manage the whole set of groups and volumes and such?
In this particular case I want to create and mount various non-root
partitions on which later applications will be installed. Due to slightly
different install procedures on some boxes the base volume group names
are different and so I need to determine what the volume group is called
before calling lvs to create the logical volume/partion (which takes
the volume group as one of the parameters).

Thus until now I''ve been using a custom define (which I sent to this
list) to create the logical volume of the specified size, format
and mount it if it is not already mounted.  That''s fine if I know the
volume group name but that (unfortunately) varies between different
types of servers.

So now I want to be able to check the number of volume groups on the
server, and if it is only one (the normal case) use _that_ volume
group as the name for creating logical volumes. In other cases the
sysadmin will have to resolve the problem.
> It''s not like you can iterate over the groups in Puppet or
anything.
No, but if I could use the information about existing volume groups
I could proceed further by creating logical volumes on top of them,
and then further continue with application installation and configuration.
> > So how should I store this? Facter would seem to be the best thing to 
> > adjust adding some custom facts but from what I can see all facter   
> > facts 
> > are single scalar values. 
>  
> > So am I approaching the problem incorrectly? My initial thought is 
> > that I''d like to populate some sort of variable
volume_group_info as a
> > hash of hashes, the first hash being indexed on the volume group names
> > and the second on the logical volume group names in each volume group.
>  
> The problem is that Puppet isn''t really set up to use this hash of
> hashes to make resources, and really, what''s the value of doing so
> anyway, since you''d just be telling Puppet to manage what
it''s already
> discovered, right?
Or using what it has already discovered to "fix missing elements", in
this case missing partitions, which need to be built.

You have a facility to mount non-mounted partitions. How is this any
different?

Or should I be doing this by creating custom puppet functions which
return a list of volume group names, or a list of logical volumes for
each volume group?

Perhaps after coming from cfengine (which has it''s own issues)
I''m more
used to be able to create "custom facts" or "custom
conditions" based
on running a simple shell script, and using those facts/conditions to
later perform other tasks. So I''m trying to see how this should be
solved
using puppet.

The only thing that surprises me is that I don''t see recipes or
archives
which mention the use of LVM for configuring servers with puppet yet
this seems to be such a basic task of building a server. And at least
2 platforms I know use LVM: Linux and AIX, though I imagine other UNIX
platforms do too.

Simon



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sjmudd@pobox.com (Simon J Mudd) writes:
> The only thing that surprises me is that I don''t see recipes or
archives
> which mention the use of LVM for configuring servers with puppet yet
> this seems to be such a basic task of building a server. And at least
> 2 platforms I know use LVM: Linux and AIX, though I imagine other UNIX
> platforms do too.
Actually I''m wrong. There is a ticket
http://reductivelabs.com/trac/puppet/ticket/475 which mentions
this. One thing perhaps it''s missing is having the list of volume
groups and logical volumes in a place that can be used to check for
their existence.

For volume groups something list a list/hash of volume groups. If this
is not possible a : separated list of volume groups. That would be something
like:

# vgs
  VG              #PV #LV #SN Attr   VSize   VFree
  xxxxx.wl0.org     1  23   0 wz--n- 465.56G 186.53G
  usbdisk.wl0.org   1   2   0 wz--n- 465.56G  32.00M

or $volume_groups = "xxxxx.wl0.org:usbdisk.wl0.org"

Logical volume information is more difficult as you have multiple
logical volumes under each volume group so storing in a scalar is ugly
and would produce very large strings.

So I have something similar on one of my machines:

# lvs
  LV                          VG              Attr   LSize   Origin Snap%  Move
Log Copy%  Convert
  lv.vm.fc7                   vg00            -wi-ao  10.00G
  lv.vm.fedora8               vg00            -wi-ao  10.00G
  lv.vm.fedora9               vg00            -wi-ao  10.00G
  lv.vm.rhel5                 vg00            -wi-ao  10.00G
  lv.vm.rhel4                 vg00            -wi-ao  10.00G
  lv.vm.rhel3                 vg00            -wi-ao  10.00G
  lvbackup                    vg00            -wi-ao  10.00G
  lvhome                      vg00            -wi-ao   1.00G
  lvmirror                    vg00            -wi-ao  10.00G
  lvopenpkg                   vg00            -wi-ao   5.00G
  lvroot                      vg00            -wi-ao  20.00G
  lvswap                      vg00            -wi-ao   4.00G
  lvtmp                       vg00            -wi-ao   1.00G
  lvvar                       vg00            -wi-ao   2.00G
  lvusr.local.rhel4           vg00            -wi-ao   1.00G
  LogVol01                    usbdisk         -wi-a-   1.94G
  LogVol00                    usbdisk         -wi-ao 463.59G

And this would give rather a huge scalar value if vg/lv were
concatenated and colon separated.

Ideally I''d like to be able to check

vg_exists( ''usbdisk'' )
lv_exists( ''usbdisk/LogVol00'' )

It seems that the puppet functions are run on the server and not on
the client so I''m not sure how I could write a function to
collect/return the information I need as obviously it needs to be run
on the client to be of any use. Again I may be misunderstanding something.

Writing shell scripts which return an appropriate exist status to
perform these tests is trivial, but I don''t see how to collect the
information and then use it elsewhere from within puppet.

Simon














>
> Simon
>
>
>
> 
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