$ sudo apt-get upgrade --download-only
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following package was automatically installed and is no longer required:
  linux-image-3.13.0-46-generic
Use 'apt-get autoremove' to remove it.
The following packages have been kept back:
  linux-image-virtual
The following packages will be upgraded:
  apt apt-utils icedtea-7-jre-jamvm libapt-inst1.5 libapt-pkg4.12
  libmysqlclient18 mysql-client-5.5 mysql-client-core-5.5 mysql-common
  mysql-server mysql-server-5.5 mysql-server-core-5.5 openjdk-7-jre
  openjdk-7-jre-headless tzdata tzdata-java
16 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
E: Could not get lock /lock - open (11: Resource temporarily unavailable)
E: Unable to lock directory /