進入docker後，發現很不方便，很多命令都不能用，特別是vi，vim等。
在docker下，執行apt-get install vi，安裝vi，但是返回如下結果
root@0bb4d5341a2b:/etc/mysql/mysql.conf.d# apt-get install vi
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package vi
再嘗試一下apt-get install vim，返回如下結果
root@0bb4d5341a2b:/etc/mysql/mysql.conf.d# apt-get install vim
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package vim
怎麼辦呢，那就執行apt-get update，執行結果如下：
root@0bb4d5341a2b:/etc/mysql/mysql.conf.d# apt-get update
Get:1 http://repo.mysql.com/apt/debian stretch InRelease [19.2 kB]
Get:5 http://repo.mysql.com/apt/debian stretch/mysql-5.6 amd64 Packages [4744 B]
Get:3 http://security-cdn.debian.org/debian-security stretch/updates InRelease [94.3 kB]
Ign:2 http://cdn-fastly.deb.debian.org/debian stretch InRelease
Get:4 http://cdn-fastly.deb.debian.org/debian stretch-updates InRelease [91.0 kB]
Get:7 http://security-cdn.debian.org/debian-security stretch/updates/main amd64 Packages [485 kB]
Get:6 http://cdn-fastly.deb.debian.org/debian stretch Release [118 kB]
Get:8 http://cdn-fastly.deb.debian.org/debian stretch-updates/main amd64 Packages [11.1 kB]
Get:9 http://cdn-fastly.deb.debian.org/debian stretch Release.gpg [2434 B]
Get:10 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 Packages [7084 kB]
Fetched 7909 kB in 2min 13s (59.3 kB/s)
Reading package lists... Done
然後再來執行 apt-get install vim，返回如下結果