我的ubuntu 版本是 18.04.1 ，剛纔安裝 好的，乾淨的系統，如有同學之前安裝過，必須卸載後，才能重新安裝
具體安裝步驟如下
一、設置倉庫
爲了設置倉庫，需要有幾個前置步驟，完成之後纔是真正設置倉庫，具體如下
1、更新 apt 包索引。
sudo apt-get update
執行結果如下
2、安裝 apt 依賴包，用於通過HTTPS來獲取倉庫:
sudo apt-get install apt-transport-https ca-certificates curl gnupg-agent software-properties-common
執行結果如下
3、添加 Docker 的官方 GPG 密鑰：
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
執行結果如下
結果爲ok，表示成功了
9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88 這個官方密鑰，可驗證剛纔設置的結果
具體如下
sudo apt-key fingerprint 0EBFCD88 （注： sudo apt-key fingerprint 後面是官方密鑰後面的8位）
執行結果如下
這個表示驗證成功
4、設置穩定版倉庫
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
執行結果如下
二、安裝 Docker Engine-Community
1、更新 apt 包索引
sudo apt-get update
執行結果如下
2、安裝最新版本的 Docker Engine-Community 和 containerd ，或者轉到下一步安裝特定版本：
sudo apt-get install docker-ce docker-ce-cli containerd.io
執行結果如下
root@zs:~$ sudo apt-get install docker-ce docker-ce-cli containerd.io
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
aufs-tools cgroupfs-mount libltdl7 pigz
The following NEW packages will be installed:
aufs-tools cgroupfs-mount containerd.io docker-ce docker-ce-cli libltdl7 pigz
0 upgraded, 7 newly installed, 0 to remove and 24 not upgraded.
Need to get 85.8 MB of archives.
After this operation, 385 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://cn.archive.ubuntu.com/ubuntu bionic/universe amd64 pigz amd64 2.4-1 [57.4 kB]
Get:2 http://cn.archive.ubuntu.com/ubuntu bionic/universe amd64 aufs-tools amd64 1:4.9+20170918-1ubuntu1 [104 kB]
Get:3 https://download.docker.com/linux/ubuntu bionic/stable amd64 containerd.io amd64 1.2.13-1 [20.1 MB]
Get:4 http://cn.archive.ubuntu.com/ubuntu bionic/universe amd64 cgroupfs-mount all 1.4 [6,320 B]
Get:5 http://cn.archive.ubuntu.com/ubuntu bionic/main amd64 libltdl7 amd64 2.4.6-2 [38.8 kB]
Get:6 https://download.docker.com/linux/ubuntu bionic/stable amd64 docker-ce-cli amd64 5:19.03.8~3-0~ubuntu-bionic [42.6 MB]
Get:7 https://download.docker.com/linux/ubuntu bionic/stable amd64 docker-ce amd64 5:19.03.8~3-0~ubuntu-bionic [22.9 MB]
Fetched 85.8 MB in 45s (1,890 kB/s)
Selecting previously unselected package pigz.
(Reading database ... 66987 files and directories currently installed.)
Preparing to unpack .../0-pigz_2.4-1_amd64.deb ...
Unpacking pigz (2.4-1) ...
Selecting previously unselected package aufs-tools.
Preparing to unpack .../1-aufs-tools_1%3a4.9+20170918-1ubuntu1_amd64.deb ...
Unpacking aufs-tools (1:4.9+20170918-1ubuntu1) ...
Selecting previously unselected package cgroupfs-mount.
Preparing to unpack .../2-cgroupfs-mount_1.4_all.deb ...
Unpacking cgroupfs-mount (1.4) ...
Selecting previously unselected package containerd.io.
Preparing to unpack .../3-containerd.io_1.2.13-1_amd64.deb ...
Unpacking containerd.io (1.2.13-1) ...
Selecting previously unselected package docker-ce-cli.
Preparing to unpack .../4-docker-ce-cli_5%3a19.03.8~3-0~ubuntu-bionic_amd64.deb ...
Unpacking docker-ce-cli (5:19.03.8~3-0~ubuntu-bionic) ...
Selecting previously unselected package docker-ce.
Preparing to unpack .../5-docker-ce_5%3a19.03.8~3-0~ubuntu-bionic_amd64.deb ...
Unpacking docker-ce (5:19.03.8~3-0~ubuntu-bionic) ...
Selecting previously unselected package libltdl7:amd64.
Preparing to unpack .../6-libltdl7_2.4.6-2_amd64.deb ...
Unpacking libltdl7:amd64 (2.4.6-2) ...
Setting up aufs-tools (1:4.9+20170918-1ubuntu1) ...
Setting up containerd.io (1.2.13-1) ...
Created symlink /etc/systemd/system/multi-user.target.wants/containerd.service → /lib/systemd/system/containerd.service.
Setting up cgroupfs-mount (1.4) ...
Setting up libltdl7:amd64 (2.4.6-2) ...
Setting up docker-ce-cli (5:19.03.8~3-0~ubuntu-bionic) ...
Setting up pigz (2.4-1) ...
Setting up docker-ce (5:19.03.8~3-0~ubuntu-bionic) ...
Created symlink /etc/systemd/system/multi-user.target.wants/docker.service → /lib/systemd/system/docker.service.
Created symlink /etc/systemd/system/sockets.target.wants/docker.socket → /lib/systemd/system/docker.socket.
Processing triggers for libc-bin (2.27-3ubuntu1) ...
Processing triggers for systemd (237-3ubuntu10.38) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for ureadahead (0.100.0-21) ...
3、列出可用版本（注：這裏安裝特定版本，所以安裝前需要列出可用版本）
apt-cache madison docker-ce
執行結果如下：
4、安裝
這裏選擇 5:19.03.8~3-0~ubuntu-bionic 列表中第一個版本，這只是個人建議，這個版本不是最新也不是最舊，其實使用起來差距不大，
sudo apt-get install docker-ce=5:18.09.0~3-0~ubuntu-bionic docker-ce-cli=5:18.09.0~3-0~ubuntu-bionic containerd.io
執行結果如下
5、測試是否成功
sudo docker run hello-world
執行結果如下，說明安裝成功了
