docker图像的默认命令

Question

如果不实际从映像创建新容器，我如何知道容器使用基本映像运行的默认命令？

是不是我遗漏了一些概念？我正在用一个基本图像写一个dockerfile，但我不知道该在CMD部分放什么。

Answer 1

docker image inspect <IMAGE>将为您提供更多详细信息。

例如：

$ docker pull nginx
$ docker image inspect nginx:latest
...
"0":
"Config": {
...
"Cmd": [
"nginx",
"-g",
"daemon off;"
],
...
}

因此，对于Nginx，它是[nginx, -g, daemon off;]

或者，如果安装了jq，则ubuntu:20.04:的输出

$ docker pull ubuntu:20.04
$ docker image inspect ubuntu:20.04 | jq '.[0].Config.Cmd'
[
"/bin/bash"
]

Answer 2

您总是可以在终端上执行docker image inspect <image>，在那里您将获得一堆信息。

我运行docker image inspect busybox(只是一些随机图像(，得到了以下结果

[
{

"Parent": "",
"Comment": "",
"Created": "2021-05-04T00:19:49.531663542Z",
"Container": "22c781af50cbbf2c31a3fb57c21d4dcfb266d6691441657088db6750d4068d22",
"ContainerConfig": {
"Hostname": "22c781af50cb",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
],
"Cmd": [
"/bin/sh",
"-c",
"#(nop) ",
"CMD ["sh"]"
],

"Volumes": null,
"WorkingDir": "",
"Entrypoint": null,
"OnBuild": null,
"Labels": {}
},
"DockerVersion": "19.03.12",
"Author": "",
"Config": {
"Hostname": "",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
],
"Cmd": [
"sh"
],

"Volumes": null,
"WorkingDir": "",
"Entrypoint": null,
"OnBuild": null,
"Labels": null
},
"Architecture": "amd64",
"Os": "linux",
"Size": 1235829,
"VirtualSize": 1235829,
"GraphDriver": {
"Data": {
},
"Name": "overlay2"
},
"RootFS": {
"Type": "layers",
},
"Metadata": {
"LastTagTime": "0001-01-01T00:00:00Z"
}
}
]

在这里您可以看到CMD字段