$ uname -r
3.0.0-12-generic
$ sudo apt-get install linux-headers-3.0.0-12-generic
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  linux-headers-3.0.0-12
The following NEW packages will be installed:
  linux-headers-3.0.0-12 linux-headers-3.0.0-12-generic
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/12.0 MB of archives.
After this operation, 98.2 MB of additional disk space will be used.
Do you want to continue [Y/n]?