是否有可能将 Windows 上的 LXSS 从 14.04 更新到 16.04？
sudo do-release-upgrade
不起作用。
后sudo apt upgrade不断出现以下错误：
$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n]
Setting up grub-pc (2.02~beta2-9ubuntu1.11) ...
grub-probe: error: failed to get canonical path of `rootfs'.
grub-probe: error: failed to get canonical path …在Linux中如何使用cp一个可以将文件复制到目标，但如果目标存在，则仅当目标比源旧时才覆盖？
cp -f总是覆盖，但只有当目标比源旧时才需要覆盖。