新部署的云服务器出现如下错误：
root@iZj6cbjalvhsw0fhndmm5xZ:~# apt-get install git Reading package lists... Done Building dependency tree Reading state information... Done The following additional packages will be installed: git-man liberror-perl Suggested packages: git-daemon-run | git-daemon-sysvinit git-doc git-el git-email git-gui gitk gitweb git-arch git-cvs git-mediawiki git-svn The following NEW packages will be installed: git git-man liberror-perl 0 upgraded, 3 newly installed, 0 to remove and 0 not upgraded. Need to get 3,898 kB/3,918 kB of archives. After this operation, 25.6 MB of additional disk space will be used. Do you want to continue? [Y/n] y Ign:1 http://mirrors.cloud.aliyuncs.com/ubuntu xenial-updates/main i386 git-man all 1:2.7.4-0ubuntu1.2 Ign:2 http://mirrors.cloud.aliyuncs.com/ubuntu xenial-security/main amd64 git amd64 1:2.7.4-0ubuntu1.2 Ign:1 http://mirrors.cloud.aliyuncs.com/ubuntu xenial-security/main amd64 git-man all 1:2.7.4-0ubuntu1.2 Err:2 http://mirrors.cloud.aliyuncs.com/ubuntu xenial-security/main amd64 git amd64 1:2.7.4-0ubuntu1.2 404 Not Found Err:1 http://mirrors.cloud.aliyuncs.com/ubuntu xenial-security/main i386 git-man all 1:2.7.4-0ubuntu1.2 404 Not Found Err:1 http://mirrors.cloud.aliyuncs.com/ubuntu xenial-security/main i386 git-man all 1:2.7.4-0ubuntu1.2 404 Not Found E: Failed to fetch http://mirrors.cloud.aliyuncs.com/ubuntu/pool/main/g/git/git-man_2.7.4-0ubuntu1.2_all.deb 404 Not Found E: Failed to fetch http://mirrors.cloud.aliyuncs.com/ubuntu/pool/main/g/git/git_2.7.4-0ubuntu1.2_amd64.deb 404 Not Found E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
（这不很明显是一些安装源失效，甚至还有命令提示）为了避免像我一样看到错误就百度一波，结果没找到一个靠谱的方法。
超简单，更新一下源就可以了。
sudo apt-get update