/boot not enough space
uname -r //当前kernel版本
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dpkg -l | grep linux-image | cut -d " " -f3 //当前所有安装的kernel版本
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sudo apt-get purge linux-image-3.5.0-{17,18,19,21,22,23,24}-generic
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一句话解决问题
sudo apt-get purge $(dpkg -l | grep linux-{image,headers}-[0-9]+ | cut -d " " -f3 | egrep -v $(uname -r | sed -r "s/-[a-z]+//"))