Puppet users - Sep 2009 - Adding comments to config files with augeas

Hi,

I''ve got a ''define'' that I use to set kernel
parameters in
/etc/sysctl.conf using the augeas type.  It works well, but I''d like
to be able to add a comment line directly above my the parameter to
explain what it does and why it''s been changed.  We currently just add
a comment in site.pp, but that''s not much use to local admins.

Unfortunately, I can''t seem to find any way of inserting arbitrary
strings using augeas.  I tried the ''insert'' command, but after
some
reading I understand now that ins/insert is only meant for controlling
where a parameter should be put in the file.

Here''s a simplified version of a (broken) sysctl define.  I know why
this doesn''t work - it''s just to give an idea of what
I''d like to get
working!

define sysctl::config ($value, $comment) {
  augeas { "sysctl_$name":
    context => "/files/etc/sysctl.conf",
    changes => [
      "set $name $value",
      "insert ''# ${comment}'' before $name",
    ],
    onlyif  => "get $name != $value",
  }
}


Anyone have any ideas?

TIA,
Bryan

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On Thu, 2009-09-10 at 16:42 +0100, Bryan Ross wrote:
> Unfortunately, I can''t seem to find any way of inserting arbitrary
> strings using augeas.  I tried the ''insert'' command, but
after some
> reading I understand now that ins/insert is only meant for controlling
> where a parameter should be put in the file.
Comments for most files[1] show up as nodes with label
''#comment'' and a
value that contains the comment without the leading ''#[ \t]*''.
Therefore, to add a comment, you need to first create a
''#comment'' node
and then set it to whatever you want the comment to be.
> Here''s a simplified version of a (broken) sysctl define.  I know
why
> this doesn''t work - it''s just to give an idea of what
I''d like to get
> working!
> 
> define sysctl::config ($value, $comment) {
>   augeas { "sysctl_$name":
>     context => "/files/etc/sysctl.conf",
>     changes => [
>       "set $name $value",
>       "insert ''# ${comment}'' before $name",
>     ],
>     onlyif  => "get $name != $value",
>   }
> }
Almost ;) What you want for changes is

  changes => [
    "set $name $value",
    "insert #comment before $name",
    "set #comment[last()] ''Look Ma, a comment''"
  ]

David

[1] There are some inconsistencies that we are gradually fixing; the
lens for sysctl.conf gets it right.


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2009/9/10 David Lutterkort <lutter@redhat.com>:
> Comments for most files[1] show up as nodes with label
''#comment'' and a
> value that contains the comment without the leading ''#[
\t]*''.
> Therefore, to add a comment, you need to first create a
''#comment'' node
> and then set it to whatever you want the comment to be.
Many thanks David - works perfectly!  I can also understand where my
thinking was wrong.

For anyone googling this, here''s a working example:
node default {
  sysctl::config { "fs.file-max":
    value => 65536,
    comment => "Maximum number of filehandles",
  }
}

class sysctl {
  define config ($value, $comment) {
    file { "/etc/sysctl.conf":
      mode => 644,
      owner => root,
      group => root,
      ensure => present,
    }

    augeas { "sysctl_$name":
      context => "/files/etc/sysctl.conf",
      changes => [
        "set $name $value",
        "insert #comment before $name",
        "set #comment[last()] ''$comment''"
      ],
      onlyif  => "get $name != $value",
      notify  => Exec["/sbin/sysctl -p"],
    }

    exec { "/sbin/sysctl -p":
      subscribe   => File["/etc/sysctl.conf"],
      refreshonly => true,
    }
  }
}

Cheers,
Bryan

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