class sysctl {

  file { "sysctl_$name":
    path => "/etc/sysctl.conf",
    mode => 644,
    owner => root,
    group => root,
    ensure => present,
  }
  
  define config ($value, $comment) {
    augeas { "sysctl_$name":
      context => "/files/etc/sysctl.conf",
      changes => [ "set $name $value", "insert #comment before $name",
                   "set #comment[last()] '$comment'" ],
      onlyif  => "get $name != $value",
      notify  => Exec["sysctl_$name"],
    }
    exec { "sysctl_$name":
      command => "/sbin/sysctl -p",
      subscribe   => File["sysctl_$name"],
      refreshonly => true,
    }
  }
}


 sysctl::config { "xen.independent_wallclock":
   value => 1,
   comment => "see http://wiki.debian.org/Xen#A.27clocksource.2BAC8-0.3ATimewentbackwards.27"
}


err: Could not run Puppet configuration client: Cannot alias File[sysctl_xen.independent_wallclock] to /etc/sysctl.conf; resource File[/etc/sysctl.conf] already exists