The following packages were automatically installed and are no longer required:
  linux-headers-3.19.0-25 linux-headers-3.19.0-25-generic
  linux-headers-3.19.0-26 linux-headers-3.19.0-26-generic
  linux-image-3.19.0-25-generic linux-image-3.19.0-26-generic
  linux-image-extra-3.19.0-25-generic linux-image-extra-3.19.0-26-generic
  linux-signed-image-3.19.0-26-generic
Use 'apt-get autoremove' to remove them.