linux /boot 没有足够的空间安装

参考：
https://askubuntu.com/questions/668582/false-disk-full-error-apt-get-unable-to-install-or-remove

$ sudo rm -rv ${TMPDIR:-/var/tmp}/mkinitramfs-*  
                                  ## In Ubuntu 16.04 and earlier there may be leftover temporary
                                  ## files to delete.
                                  ## See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=814345

$ uname -r                        ## This command identifies the currently-running kernel
4.2.0-21-generic                  ## This is the current kernel.
                                  ## DO NOT REMOVE it!

$ dpkg -l | tail -n +6 | grep -E 'linux-image-[0-9]+' | grep -Fv $(uname -r)
                                  ## This command lists all the kernels excluding the booted
                                  ## kernel in the package database, and their status.
rc  linux-image-4.2.0-14-generic  ## The oldest kernel in the database
                                  ## Status 'rc' means it's already been removed
ii  linux-image-4.2.0-15-generic  ## The oldest installed kernel. Eligible for removal.
                                  ## Status 'ii' means Installed.
ii  linux-image-4.2.0-16-generic  ## Another old installed kernel. Eligible for removal
ii  linux-image-4.2.0-18-generic  ## Another old installed kernel. Eligible for removal
ii  linux-image-4.2.0-19-generic  ## The previous good kernel. Keep
iU  linux-image-4.2.0-22-generic  ## DO NOT REMOVE. Status 'iU' means it's not installed,
                                  ## but queued for install in apt.
                                  ## This is the package we want apt to install.

                                  ## Purge the oldest kernel package using dpkg instead of apt.
                                  ## First you need to remove the image initrd.img file manually
                                  ## due to Bug #1678187.
$ sudo update-initramfs -d -k 4.2.0-15-generic
$ sudo dpkg --purge linux-image-4.2.0-15-generic linux-image-extra-4.2.0-15-generic
                                  ## If the previous command fails, some installed package
                                  ## depends on the kernel. The output of dpkg tells the name
                                  ## of the package. Purge it first.

                                  ## Also purge the respective header package.
$ sudo dpkg --purge linux-headers-4.2.0-15-generic
                                  ## Try also purging the common header package.
$ sudo dpkg --purge linux-headers-4.2.0-15
                                  ## Do not worry, if the previous command fails.

$ sudo apt-get -f install         ## Try to fix the broken dependency.

I followed this with:

sudo apt-get autoremove --purge