While upgrading Ubuntu to 14.04 you receive the error “not enough free disk space” on ‘/boot’ you need at least 57m free.
Check your space:
fdisk -l &&df -h
List unused images:
dpkg -l | grep linux-image
The fix, this removes all unused kernels:
dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/(.*)-([^0-9]+)/1/")"'/d;s/^[^ ]* [^ ]* ([^ ]*).*/1/;/[0-9]/!d' | xargs sudo apt-get -y purge
Check space, reboot and rerun upgrade:
fdisk -l &&df -h
References:
Ubuntu Cleanup: How to Remove All Unused Linux Kernel Headers
Can’t upgrade due to low disk space on /boot