title: android sdk missing system-images
body: <p>I'm trying to setup multiple target on a CI server (CentOS 64_x86) for automated Android app testing, which would run multiple emulator heedlessly. After extracting the latest SDK from 
      <a href="http://dl.google.com/android/adt/adt-bundle-linux-x86_64-20130729.zip" rel="noreferrer">http://dl.google.com/android/adt/adt-bundle-linux-x86_64-20130729.zip</a>
  and run,
      android update sdk --no-ui
  I suppose I should have installed all existing component properly, but 2 problems found,</p>
  
  <ol>
  <li><p>After selected "ARM EABI v7a System Image, Android API 18" and agreed "android-sdk-license-bcbbd656", it seems installed properly but next time I update sdk it shows up again and always installable. Note that I installed them through command line where no window UI available, not sure if any difference here.. (however the emulator for API 18 is working...)</p></li>
  <li><p>Looking at the folder $SDK_PATH/system-images, only "android-18/armeabi-v7a" available, but compared to my another SDK installation on macbook, this same folder contains much richer content including whatever api available, not only API 18. </p></li>
  <li><p>I guess this difference above caused my 3rd issue (for example on API 15 which don't have a "system-images/android-18/armeabi-v7a"), when I run lator from an AVD like,</p></li>
  </ol>
  
  <blockquote>
    <p>emulator -no-window -port 5554 -snapshot default -avd google_api_15</p>
  </blockquote>
  
  <p>error happens</p>
  
  <pre><code>emulator: trying to load skin file '/home/abc/adt/sdk/platforms/android-15/skins/WVGA800/layout'
  emulator: skin network speed: 'full'
  emulator: skin network delay: 'none'
  emulator: ERROR: This AVD's configuration is missing a kernel file!!
  </code></pre>
  
  <p>comparing to a normal output this should be </p>
  
  <blockquote>
    <p>emulator: skin network speed: 'full' emulator: skin network delay:
    'none' emulator: autoconfig: -kernel
    /home/bamboo_master/environment/adt/sdk/add-ons/addon-google_tv_addon-google-12/images/x86//kernel-qemu
    emulator: autoconfig: -ramdisk
    /home/bamboo_master/environment/adt/sdk/add-ons/addon-google_tv_addon-google-12/images/x86//ramdisk.img
    emulator: Using initial system image:
    /home/bamboo_master/environment/adt/sdk/add-ons/addon-google_tv_addon-google-12/images/x86//system.img
    emulator: autoconfig: -data
    /home/bamboo_master/.android/avd/google_api_15.avd/userdata-qemu.img
    emulator: autoconfig: -initdata
    /home/bamboo_master/.android/avd/google_api_15.avd/userdata.img
    emulator: autoconfig: -cache
    /home/bamboo_master/.android/avd/google_api_15.avd/cache.img emulator:
    autoconfig: -snapstorage
    /home/bamboo_master/.android/avd/google_api_15.avd/snapshots.img
    emulator: Physical RAM size: 1024MB</p>
  </blockquote>
  
  <p>If my understanding is right that it's due to system-image missing, is there a way to install them? Thanks.</p>