Comment 57 for bug 1357093

Ta, "sudo apt-get autoremove --purge" only purges automatically installed packages, but in Trusty the linux kernel packages are likely to be marked as being manually installed.

If you mean /boot/initrd.img* files by gzip archives, they should be removed automatically when you purge the respective kernel package such as linux-image-3.19.0-59-generic by dpkg (or by apt).

If you have kernel junk in /boot even if dpkg does not list the kernel(s) as being installed, there may be a bug similar to Bug #1586303. You may write a separate bug report about it.

If you use Trusty or later, run purge-old-kernels without sudo in shell to get to know which package to install, if the command is not found.