Cleaning the /boot partition in Ubuntu

Eventually, the boot sector space filled with the downloaded  images which creates system issues. Following commands are useful in identifying old images in the /boot partition and purge them from the system.

Initially, use df -h command and get the information about the space of the partitions

#df -h
Filesystem                   Size  Used Avail Use% Mounted on
udev                         3.9G     0  3.9G   0% /dev
tmpfs                        787M  9.4M  778M   2% /run
/dev/mapper/ubuntu--vg-root  909G  255G  608G  30% /
tmpfs                        3.9G  348K  3.9G   1% /dev/shm
tmpfs                        5.0M  4.0K  5.0M   1% /run/lock
tmpfs                        3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/sda1                    472M  468M     0 100% /boot
tmpfs                        787M   64K  787M   1% /run/user/1000
This provides the space availability of each partition and clearly shows the /boot partition is fully filled.

Go to /boot and type following command to identify the installed images in the system

#cd /boot
#dpkg -l linux-image-\* | grep ^ii
ii  linux-image-4.4.0-108-generic       4.4.0-108.131 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-4.4.0-109-generic       4.4.0-109.132 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-4.4.0-112-generic       4.4.0-112.135 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-4.4.0-116-generic       4.4.0-116.140 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-4.4.0-121-generic       4.4.0-121.145 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-4.4.0-127-generic       4.4.0-127.153 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-4.4.0-128-generic       4.4.0-128.154 amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-extra-4.4.0-108-generic 4.4.0-108.131 amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-extra-4.4.0-109-generic 4.4.0-109.132 amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-extra-4.4.0-112-generic 4.4.0-112.135 amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-extra-4.4.0-116-generic 4.4.0-116.140 amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-extra-4.4.0-121-generic 4.4.0-121.145 amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP
ii  linux-image-extra-4.4.0-127-generic 4.4.0-127.153 amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP

Use uname command to check the current image version of the system

# uname -a 
Linux chamara-X556UAK 4.4.0-128-generic #154-Ubuntu SMP Fri May 25 14:15:18 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Use apt-get purge command to remove older versions of the images.
#  sudo apt-get purge linux-image-4.4.0-108
Reading package lists... Done
Building dependency tree      
Reading state information... Done
...
..
..
..
done
Purging configuration files for linux-image-4.4.0-108-generic (4.4.0-108.131) ...
Examining /etc/kernel/postrm.d .
run-parts: executing /etc/kernel/postrm.d/initramfs-tools 4.4.0-108-generic /boot/vmlinuz-4.4.0-108-generic
run-parts: executing /etc/kernel/postrm.d/zz-update-grub 4.4.0-108-generic /boot/vmlinuz-4.4.0-108-generic

Now you will see the space available has increased in the /boot partition