Remover Kernel antigo no Debian ou Ubuntu

Para listar os Kernels instalados

$ dpkg -l | grep linux-headers-*
____________________________________________________
ii  linux-headers-3.2.0-29                 3.2.0-29.46                             Header files related to Linux kernel version 3.2.0
ii  linux-headers-3.2.0-29-generic-pae     3.2.0-29.46                             Linux kernel headers for version 3.2.0 on 32 bit x86 SMP
ii  linux-headers-3.2.0-32                 3.2.0-32.51                             Header files related to Linux kernel version 3.2.0
ii  linux-headers-3.2.0-32-generic-pae     3.2.0-32.51                             Linux kernel headers for version 3.2.0 on 32 bit x86 SMP
ii  linux-headers-generic-pae              3.2.0.32.35                             Generic Linux kernel headers
____________________________________________________

Para descobrir qual Kernel estamos usando
$ uname -r
____________________________________________________
3.2.0-32-generic-pae
____________________________________________________ 

Para remover os mais antigos
$ apt-get remove --purge linux-headers-3.2.0-29*