ubuntu利用 alternate ISO 镜像来离线升级
运行指令：
sudo mount -t iso9660 -o loop ~/ubuntu-12.04.2-alternate-i386.iso /cdrom
sudo /cdrom/cdromupgrade
之后，出现
An upgrade from 'maverick' to 'precise' is not supported with this tool
这是怎么回事 求大神指点 linux离线升级
[解决办法]