How can I know the default command a container runs using a base image without actually creating a new container from the image?
is some concept I am missing here? I am writing a dockerfile using a base image but I dont know what to put in CMD section.
You can always do docker image inspect <image> on the terminal where you will get a bunch of information.
I run docker image inspect busybox (Just some random image), and I got the following result
[
{
"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"
}
}
]
Here you can see the CMD field