6.2.3　拉取镜像

Docker主机安装之后，本地并没有镜像。

Linux Docker主机本地镜像仓库通常位于 /var/lib/docker/<storage-driver> ，Windows Docker主机则是 C:\ProgramData\docker\windowsfilter 。

读者可以使用以下命令检查Docker主机的本地仓库中是否包含镜像。

$ docker image ls
REPOSITORY  TAG      IMAGE ID      CREATED      SIZE

将镜像取到Docker主机本地的操作是拉取。所以，如果读者想在Docker主机使用最新的Ubuntu镜像，需要拉取它。通过下面的命令可以将镜像拉取到本地，并观察其大小。

注：

如果读者参考Linux示例，并且还没有将当前用户加入到本地Docker UNIX组中，则需要在下面的命令前面添加sudo。

Linux示例如下。

$ docker image pull ubuntu:latest
latest: Pulling from library/ubuntu
b6f892c0043b: Pull  complete
55010f332b04: Pull  complete
2955fb827c94: Pull  complete
3deef3fcbd30: Pull  complete
cf9722e506aa: Pull  complete
Digest: sha256:38245....44463c62a9848133ecb1aa8
Status: Downloaded newer image for ubuntu:latest
$ docker image pull alpine:latest
latest: Pulling from library/alpine cfc728c1c558:
Pull complete
Digest: sha256:c0537...497c0a7726c88e2bb7584dc96
Status: Downloaded newer image for alpine:latest
$ docker image ls
REPOSITORY  TAG     IMAGE ID       CREATED       SIZE
ubuntu      latest  ebcd9d4fca80   3 days ago    118MB
alpine      latest  02674b9cb179   8 days ago    3.99MB

Windows示例如下。

> docker image pull microsoft/powershell:nanoserver
nanoserver: Pulling from microsoft/powershell
bce2fbc256ea: Pull complete
58f68fa0ceda: Pull complete
04083aac0446: Pull complete
e42e2e34b3c8: Pull complete
0c10d79c24d4: Pull complete
715cb214dca4: Pull complete
a4837c9c9af3: Pull complete
2c79a32d92ed: Pull complete
11a9edd5694f: Pull complete
d223b37dbed9: Pull complete
aee0b4393afb: Pull complete
0288d4577536: Pull complete
8055826c4f25: Pull complete
Digest: sha256:090fe875...fdd9a8779592ea50c9d4524842
Status: Downloaded newer image for microsoft/powershell:nanoserver
>
> docker image pull microsoft/dotnet:latest
latest: Pulling from microsoft/dotnet
bce2fbc256ea: Already exists
4a8c367fd46d: Pull complete
9f49060f1112: Pull complete
0334ad7e5880: Pull complete
ea8546db77c6: Pull complete
710880d5cbd5: Pull complete
d665d26d9a25: Pull complete
caa8d44fb0b1: Pull complete
cfd178ff221e: Pull complete
Digest: sha256:530343cd483dc3e1...6f0378e24310bd67d2a
Status: Downloaded newer image for microsoft/dotnet:latest
>
> docker image ls
REPOSITORY            TAG         IMAGE ID   CREATED     SIZE
microsoft/dotnet      latest      831..686d  7 hrs ago   1.65 GB
microsoft/powershell  nanoserver  d06..5427  8 days ago  1.21 GB

就像读者看到的一样，刚才拉取的镜像已经存在于 Docker 主机本地仓库中。同时可以看到Windows镜像要远大于Linux镜像，镜像中分层也更多。