Docker - Index of commands

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docker inspect

Usage :

Return low-level information on Docker objects

Flags :

Flag Usage
-f formatString
--format=formatString		 Format the output using the given Go template (details : 1, 2)
  • By default, data is returned as a JSON array.
  • formatString is not just a list of output format flags (as seen with other tools) but rather a mix of :
    • the list of queried fields
    • and a function (if any) to combine them to build the result
    like in the pseudo-code : join(', ', (field1, field2, field3))

Example :

Let's discover docker inspect :

  • Learn everything about the containerId container :
    docker inspect containerId
  • Extract specific values :
    docker inspect -f '{{.LogPath}}' containerId
    /var/lib/docker/containers/containerId_full/containerId_full-json.log
    docker inspect -f '{{.HostConfig.Binds}}' containerId
    [/opt/docker/myApp/myApp.json:/etc/myApp.json:rw]
  • Values only or keys + values :
    docker inspect -f '{{.State}}' containerId
    {running true false false false false 5654 0  2020-09-09T09:49:07.578164883Z 0001-01-01T00:00:00Z <nil>}
    docker inspect -f '{{json .State}}' containerId
    {"Status":"running","Running":true,"Paused":false,"Restarting":false,"OOMKilled":false,"Dead":false,"Pid":5654,"ExitCode":0,"Error":"","StartedAt":"2020-09-09T09:49:07.578164883Z","FinishedAt":"0001-01-01T00:00:00Z"}

Output formatting hacks :

jq :

Some experienced users prefer jq as an alternative to --format.

Python :

And if jq is not available, Python comes to the rescue :
  • raw result (JSON array) :
    docker inspect -f '{{.State}}' containerId
    {running true false false false false 5654 0  2020-09-09T09:49:07.578164883Z 0001-01-01T00:00:00Z <nil>}
  • keys + values as a JSON string :
    docker inspect -f '{{json .State}}' containerId
    {"Status":"running","Running":true,"Paused":false,"Restarting":false,"OOMKilled":false,"Dead":false,"Pid":5654,"ExitCode":0,"Error":"","StartedAt":"2020-09-09T09:49:07.578164883Z","FinishedAt":"0001-01-01T00:00:00Z"}
  • pretty print of data (with keys sorted alphabetically) :
    docker inspect -f '{{json .State}}' containerId | python -m json.tool
    {
    "Dead": false,
    "Error": "",
    "ExitCode": 0,
    "FinishedAt": "0001-01-01T00:00:00Z",
    "OOMKilled": false,
    "Paused": false,
    "Pid": 5654,
    "Restarting": false,
    "Running": true,
    "StartedAt": "2020-09-09T09:49:07.578164883Z",
    "Status": "running"
}
mail

docker exec

Usage :

Run a command in a running container

Flags :

Flag Usage
-i --interactive Keep STDIN open even if not attached
-t --tty Allocate a pseudo-TTY
-u --user specify a username or UID

Example :

Run a command in a container as a specific user :

  • docker exec -u bob -it 9f78e57b54d9 whoami
    bob
  • Open a shell as bob (details) :
    docker exec -u bob -it 9f78e57b54d9 sh