disk full at /boot (Ubuntu)

Disk full at /boot of Ubuntu system after several months system update as follow

It is really inconvenient to maintain this issue.  Is Ubuntu default boot directory size 200MiB? Anyway, the following commands could remove unused linux-image at /boot

# uname -r
3.2.0-40-generic
# dpkg --list 'linux-image*'
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name             Version          Description
+++-================-================-================================================
un  linux-image      <none>           (no description available)
un  linux-image-3.0  <none>           (no description available)
ii  linux-image-3.2. 3.2.0-23.36      Linux kernel image for version 3.2.0 on 64 bit x
rc  linux-image-3.2. 3.2.0-24.39      Linux kernel image for version 3.2.0 on 64 bit x
rc  linux-image-3.2. 3.2.0-27.43      Linux kernel image for version 3.2.0 on 64 bit x
rc  linux-image-3.2. 3.2.0-29.46      Linux kernel image for version 3.2.0 on 64 bit x
rc  linux-image-3.2. 3.2.0-30.48      Linux kernel image for version 3.2.0 on 64 bit x
rc  linux-image-3.2. 3.2.0-31.50      Linux kernel image for version 3.2.0 on 64 bit x
rc  linux-image-3.2. 3.2.0-32.51      Linux kernel image for version 3.2.0 on 64 bit x
ii  linux-image-3.2. 3.2.0-33.52      Linux kernel image for version 3.2.0 on 64 bit x
ii  linux-image-3.2. 3.2.0-34.53      Linux kernel image for version 3.2.0 on 64 bit x
ii  linux-image-3.2. 3.2.0-35.55      Linux kernel image for version 3.2.0 on 64 bit x
ii  linux-image-3.2. 3.2.0-36.57      Linux kernel image for version 3.2.0 on 64 bit x
ii  linux-image-3.2. 3.2.0-37.58      Linux kernel image for version 3.2.0 on 64 bit x
ii  linux-image-3.2. 3.2.0-38.61      Linux kernel image for version 3.2.0 on 64 bit x
ii  linux-image-3.2. 3.2.0-39.62      Linux kernel image for version 3.2.0 on 64 bit x
ii  linux-image-3.2. 3.2.0-40.64      Linux kernel image for version 3.2.0 on 64 bit x
ii  linux-image-3.2. 3.2.0-41.66      Linux kernel image for version 3.2.0 on 64 bit x
in  linux-image-3.2. <none>           (no description available)un  linux-image-serv <none>           (no description available)

root@halla:/home/jhlee# ls /boot/
abi-3.2.0-23-generic     config-3.2.0-36-generic      initrd.img-3.2.0-39-generic  System.map-3.2.0-40-generic
abi-3.2.0-33-generic     config-3.2.0-37-generic      initrd.img-3.2.0-40-generic  System.map-3.2.0-41-generic
abi-3.2.0-34-generic     config-3.2.0-38-generic      initrd.img-3.2.0-41-generic  vmlinuz-3.2.0-33-generic
abi-3.2.0-35-generic     config-3.2.0-39-generic      lost+found                   vmlinuz-3.2.0-34-generic
abi-3.2.0-36-generic     config-3.2.0-40-generic      memtest86+.bin               vmlinuz-3.2.0-35-generic
abi-3.2.0-37-generic     config-3.2.0-41-generic      memtest86+_multiboot.bin     vmlinuz-3.2.0-36-generic
abi-3.2.0-38-generic     grub                         System.map-3.2.0-23-generic  vmlinuz-3.2.0-37-generic
abi-3.2.0-39-generic     initrd.img-3.2.0-23-generic  System.map-3.2.0-33-generic  vmlinuz-3.2.0-38-generic
abi-3.2.0-40-generic     initrd.img-3.2.0-33-generic  System.map-3.2.0-34-generic  vmlinuz-3.2.0-39-generic
abi-3.2.0-41-generic     initrd.img-3.2.0-34-generic  System.map-3.2.0-35-generic  vmlinuz-3.2.0-40-generic
config-3.2.0-23-generic  initrd.img-3.2.0-35-generic  System.map-3.2.0-36-generic  vmlinuz-3.2.0-41-generic
config-3.2.0-33-generic  initrd.img-3.2.0-36-generic  System.map-3.2.0-37-generic
config-3.2.0-34-generic  initrd.img-3.2.0-37-generic  System.map-3.2.0-38-generic
config-3.2.0-35-generic  initrd.img-3.2.0-38-generic  System.map-3.2.0-39-generic

# apt-get remove linux-image-3.2.0-34-generic
Reading package lists... Done
Building dependency tree      
Reading state information... Done
The following packages will be REMOVED:
  linux-image-3.2.0-34-generic
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
After this operation, 149 MB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 337077 files and directories currently installed.)
Removing linux-image-3.2.0-34-generic ...
Examining /etc/kernel/postrm.d .
run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-34-generic /boot/vmlinuz-3.2.0-34-generic
update-initramfs: Deleting /boot/initrd.img-3.2.0-34-generic
run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-34-generic /boot/vmlinuz-3.2.0-34-generic
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.2.0-41-generic
Found initrd image: /boot/initrd.img-3.2.0-41-generic
Found linux image: /boot/vmlinuz-3.2.0-40-generic
Found initrd image: /boot/initrd.img-3.2.0-40-generic
Found linux image: /boot/vmlinuz-3.2.0-39-generic
Found initrd image: /boot/initrd.img-3.2.0-39-generic
Found linux image: /boot/vmlinuz-3.2.0-38-generic
Found initrd image: /boot/initrd.img-3.2.0-38-generic
Found linux image: /boot/vmlinuz-3.2.0-37-generic
Found initrd image: /boot/initrd.img-3.2.0-37-generic
Found linux image: /boot/vmlinuz-3.2.0-36-generic
Found initrd image: /boot/initrd.img-3.2.0-36-generic
Found linux image: /boot/vmlinuz-3.2.0-35-generic
Found initrd image: /boot/initrd.img-3.2.0-35-generic
Found memtest86+ image: /memtest86+.bin
done