thinking sysadmin

There’s something pretty satisfying about seeing 256TB of storage available on a machine and knowing that you’re only paying pennies for what you’re using:

> df -h /cloud/hrc/src/
Filesystem            Size  Used Avail Use% Mounted on
s3fs-1.35             256T     0  256T   0% /cloud/hrc/src

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I frequently find myself using Puppet to expand tarballs in various locations, sometimes fiddling with a directory name here or there. In fact, I do it so often, that I created a “define” for it earlier this week. This could be a little more polished, but in the spirit of sharing first drafts, here goes:

# Small define to expand a tarball at a location; assumes File[$title]
# definition of tarball and installation of pax:

define baselayout::drop_tarball($dest, $dir_name, $dir_sub='') {

  # $dest: cwd in which expansion is done
  # $dir_name: name of top level directory created in $dest
  # $dir_sub: regexp to -s for pax - not supported for .zip archives

  if ($dir_sub) {
    $regexp = "-s $dir_sub"
  } else {
    $regexp = ''
  }

  # CentOS' pax doesn't support "-j" flag; therefore, run pax after
  # bzcat in a pipeline. Twiddle path to bzcat as distro-appropriate:
  case $operatingsystem {
    CentOS: {
      $bzcat = "/usr/bin/bzcat"
    }
    Ubuntu: {
      $bzcat = "/bin/bzcat"
    }
  }
  
  # Choose expansion method based on file suffix:
  if (($title =~ /\.tar.gz$/) or ($title =~ /\.tgz$/)) {
    $expand = "/usr/bin/pax -rz $regexp < $title"
  } elsif (($title =~ /\.tar.bz2$/) or ($title =~ /\.tbz$/)) {
    $expand = "$bzcat $title | /usr/bin/pax -r $regexp"
  } elsif ( $title =~ /\.zip$/ ) {
    $expand = '/usr/bin/unzip $title'
  }
  
  exec { "drop_tarball $title":
    command => $expand,
    cwd => $dest,
    creates => "${dest}/${dir_name}",
    require => File[$title],
  }
  
}

The definition is written for Ubuntu and CentOS, assumes pax is installed on the system, and that a file resource for the tarball is defined before the definition is called. Pax is used instead of tar to facilitate renaming the top-level directory of the tarball. Zipped directories are also support, but without rename functionality.

I’ll update a gist as I develop the definition.

Comments welcome.

I’ve published two small repositories on GitHub:

• puppet-chrome: A Puppet module to install Google Chrome; and
• puppet-f5vpn: A Puppet module to install f5vpn, the command line F5 FirePass VPN Client.

Both are licensed under the GPL.

EC2 micro instances come with no swap by default – at least every micro instance that I’ve ever launched does, I’m not sure if it’s theoretically possible to launch an instance with swap. The lack of swap is probably a side-effect of the limited memory combined with EBS-only storage and concomitant risk of high EBS charges if you swap heavily.

However, if you’re willing to accept the risk of unexpected high EBS I/O costs, it’s straightforward to add swap:

# /bin/dd if=/dev/zero of=/var/swap.1 bs=1M count=1024
# /sbin/mkswap /var/swap.1
# /sbin/swapon /var/swap.1

Or, if you prefer Puppet:

class swapfile {

  exec { "create swap file":
    command => "/bin/dd if=/dev/zero of=/var/swap.1 bs=1M count=1024",
    creates => "/var/swap.1",
  }

  exec { "attach swap file":
    command => "/sbin/mkswap /var/swap.1 && /sbin/swapon /var/swap.1",
    require => Exec["create swap file"],
    unless => "/sbin/swapon -s | grep /var/swap.1",
  }
  
}