docker create

Description

Create a new container

Usage

docker create [OPTIONS] IMAGE [COMMAND] [ARG...]

Options

Parent command

Extended description

The docker create command creates a writeable container layer over the specified image and prepares it for running the specified command. The container ID is then printed to STDOUT. This is similar to docker run -d except the container is never started. You can then use the docker start <container_id> command to start the container at any point.

This is useful when you want to set up a container configuration ahead of time so that it is ready to start when you need it. The initial status of the new container is created.

Please see the run command section and the Docker run reference for more details.

Examples

Create and start a container

$ docker create -t -i fedora bash

6d8af538ec541dd581ebc2a24153a28329acb5268abe5ef868c1f1a261221752

$ docker start -a -i 6d8af538ec5

bash-4.2#

Initialize volumes

As of v1.4.0 container volumes are initialized during the docker create phase (i.e., docker run too). For example, this allows you to create the data volume container, and then use it from another container:

$ docker create -v /data --name data ubuntu

240633dfbb98128fa77473d3d9018f6123b99c454b3251427ae190a7d951ad57

$ docker run --rm --volumes-from data ubuntu ls -la /data

total 8
drwxr-xr-x  2 root root 4096 Dec  5 04:10 .
drwxr-xr-x 48 root root 4096 Dec  5 04:11 ..

Similarly, create a host directory bind mounted volume container, which can then be used from the subsequent container:

$ docker create -v /home/docker:/docker --name docker ubuntu

9aa88c08f319cd1e4515c3c46b0de7cc9aa75e878357b1e96f91e2c773029f03

$ docker run --rm --volumes-from docker ubuntu ls -la /docker

total 20
drwxr-sr-x  5 1000 staff  180 Dec  5 04:00 .
drwxr-xr-x 48 root root  4096 Dec  5 04:13 ..
-rw-rw-r--  1 1000 staff 3833 Dec  5 04:01 .ash_history
-rw-r--r--  1 1000 staff  446 Nov 28 11:51 .ashrc
-rw-r--r--  1 1000 staff   25 Dec  5 04:00 .gitconfig
drwxr-sr-x  3 1000 staff   60 Dec  1 03:28 .local
-rw-r--r--  1 1000 staff  920 Nov 28 11:51 .profile
drwx--S---  2 1000 staff  460 Dec  5 00:51 .ssh
drwxr-xr-x 32 1000 staff 1140 Dec  5 04:01 docker

Set storage driver options per container.

$ docker create -it --storage-opt size=120G fedora /bin/bash

This (size) will allow to set the container rootfs size to 120G at creation time. This option is only available for the devicemapper, btrfs, overlay2, windowsfilter and zfs graph drivers. For the devicemapper, btrfs, windowsfilter and zfs graph drivers, user cannot pass a size less than the Default BaseFS Size. For the overlay2 storage driver, the size option is only available if the backing fs is xfs and mounted with the pquota mount option. Under these conditions, user can pass any size less than the backing fs size.

Specify isolation technology for container (--isolation)

This option is useful in situations where you are running Docker containers on Windows. The --isolation=<value> option sets a container’s isolation technology. On Linux, the only supported is the default option which uses Linux namespaces. On Microsoft Windows, you can specify these values:

Specifying the --isolation flag without a value is the same as setting --isolation="default".

Dealing with dynamically created devices (--device-cgroup-rule)

Devices available to a container are assigned at creation time. The assigned devices will both be added to the cgroup.allow file and created into the container once it is run. This poses a problem when a new device needs to be added to running container.

One of the solution is to add a more permissive rule to a container allowing it access to a wider range of devices. For example, supposing our container needs access to a character device with major 42 and any number of minor number (added as new devices appear), the following rule would be added:

docker create --device-cgroup-rule='c 42:* rmw' -name my-container my-image

Then, a user could ask udev to execute a script that would docker exec my-container mknod newDevX c 42 <minor> the required device when it is added.

NOTE: initially present devices still need to be explicitly added to the create/run command