DockerCLI/docs/reference/commandline/run.md

run

Usage: docker run [OPTIONS] IMAGE [COMMAND] [ARG...]

Run a command in a new container

  -a, --attach=[]            Attach to STDIN, STDOUT or STDERR
  --add-host=[]              Add a custom host-to-IP mapping (host:ip)
  --blkio-weight=0           Block IO weight (relative weight)
  -c, --cpu-shares=0         CPU shares (relative weight)
  --cap-add=[]               Add Linux capabilities
  --cap-drop=[]              Drop Linux capabilities
  --cgroup-parent=""         Optional parent cgroup for the container
  --cidfile=""               Write the container ID to the file
  --cpu-period=0             Limit CPU CFS (Completely Fair Scheduler) period
  --cpu-quota=0              Limit CPU CFS (Completely Fair Scheduler) quota
  --cpuset-cpus=""           CPUs in which to allow execution (0-3, 0,1)
  --cpuset-mems=""           Memory nodes (MEMs) in which to allow execution (0-3, 0,1)
  -d, --detach=false         Run container in background and print container ID
  --device=[]                Add a host device to the container
  --dns=[]                   Set custom DNS servers
  --dns-search=[]            Set custom DNS search domains
  -e, --env=[]               Set environment variables
  --entrypoint=""            Overwrite the default ENTRYPOINT of the image
  --env-file=[]              Read in a file of environment variables
  --expose=[]                Expose a port or a range of ports
  --group-add=[]             Add additional groups to run as
  -h, --hostname=""          Container host name
  --help=false               Print usage
  -i, --interactive=false    Keep STDIN open even if not attached
  --ipc=""                   IPC namespace to use
  -l, --label=[]             Set metadata on the container (e.g., --label=com.example.key=value)
  --label-file=[]            Read in a file of labels (EOL delimited)
  --link=[]                  Add link to another container
  --log-driver=""            Logging driver for container
  --log-opt=[]               Log driver specific options
  --lxc-conf=[]              Add custom lxc options
  -m, --memory=""            Memory limit
  --mac-address=""           Container MAC address (e.g. 92:d0:c6:0a:29:33)
  --memory-swap=""           Total memory (memory + swap), '-1' to disable swap
  --memory-swappiness=""     Tune a container's memory swappiness behavior. Accepts an integer between 0 and 100.
  --name=""                  Assign a name to the container
  --net="bridge"             Set the Network mode for the container
  --oom-kill-disable=false   Whether to disable OOM Killer for the container or not
  -P, --publish-all=false    Publish all exposed ports to random ports
  -p, --publish=[]           Publish a container's port(s) to the host
  --pid=""                   PID namespace to use
  --privileged=false         Give extended privileges to this container
  --read-only=false          Mount the container's root filesystem as read only
  --restart="no"             Restart policy (no, on-failure[:max-retry], always)
  --rm=false                 Automatically remove the container when it exits
  --security-opt=[]          Security Options
  --sig-proxy=true           Proxy received signals to the process
  -t, --tty=false            Allocate a pseudo-TTY
  -u, --user=""              Username or UID (format: <name|uid>[:<group|gid>])
  --ulimit=[]                Ulimit options
  --uts=""                   UTS namespace to use
  -v, --volume=[]            Bind mount a volume
  --volumes-from=[]          Mount volumes from the specified container(s)
  -w, --workdir=""           Working directory inside the container

The docker run command first creates a writeable container layer over the specified image, and then starts it using the specified command. That is, docker run is equivalent to the API /containers/create then /containers/(id)/start. A stopped container can be restarted with all its previous changes intact using docker start. See docker ps -a to view a list of all containers.

There is detailed information about docker run in the Docker run reference.

The docker run command can be used in combination with docker commit to change the command that a container runs.

See the Docker User Guide for more detailed information about the --expose, -p, -P and --link parameters, and linking containers.

Examples

$ docker run --name test -it debian
root@d6c0fe130dba:/# exit 13
$ echo $?
13
$ docker ps -a | grep test
d6c0fe130dba        debian:7            "/bin/bash"         26 seconds ago      Exited (13) 17 seconds ago                         test

This example runs a container named test using the debian:latest image. The -it instructs Docker to allocate a pseudo-TTY connected to the container's stdin; creating an interactive bash shell in the container. In the example, the bash shell is quit by entering exit 13. This exit code is passed on to the caller of docker run, and is recorded in the test container's metadata.

$ docker run --cidfile /tmp/docker_test.cid ubuntu echo "test"

This will create a container and print test to the console. The cidfile flag makes Docker attempt to create a new file and write the container ID to it. If the file exists already, Docker will return an error. Docker will close this file when docker run exits.

$ docker run -t -i --rm ubuntu bash
root@bc338942ef20:/# mount -t tmpfs none /mnt
mount: permission denied

This will not work, because by default, most potentially dangerous kernel capabilities are dropped; including cap_sys_admin (which is required to mount filesystems). However, the --privileged flag will allow it to run:

$ docker run --privileged ubuntu bash
root@50e3f57e16e6:/# mount -t tmpfs none /mnt
root@50e3f57e16e6:/# df -h
Filesystem      Size  Used Avail Use% Mounted on
none            1.9G     0  1.9G   0% /mnt

The --privileged flag gives all capabilities to the container, and it also lifts all the limitations enforced by the device cgroup controller. In other words, the container can then do almost everything that the host can do. This flag exists to allow special use-cases, like running Docker within Docker.

$ docker  run -w /path/to/dir/ -i -t  ubuntu pwd

The -w lets the command being executed inside directory given, here /path/to/dir/. If the path does not exists it is created inside the container.

$ docker  run  -v `pwd`:`pwd` -w `pwd` -i -t  ubuntu pwd

The -v flag mounts the current working directory into the container. The -w lets the command being executed inside the current working directory, by changing into the directory to the value returned by pwd. So this combination executes the command using the container, but inside the current working directory.

$ docker run -v /doesnt/exist:/foo -w /foo -i -t ubuntu bash

When the host directory of a bind-mounted volume doesn't exist, Docker will automatically create this directory on the host for you. In the example above, Docker will create the /doesnt/exist folder before starting your container.

$ docker run --read-only -v /icanwrite busybox touch /icanwrite here

Volumes can be used in combination with --read-only to control where a container writes files. The --read-only flag mounts the container's root filesystem as read only prohibiting writes to locations other than the specified volumes for the container.

$ docker run -t -i -v /var/run/docker.sock:/var/run/docker.sock -v ./static-docker:/usr/bin/docker busybox sh

By bind-mounting the docker unix socket and statically linked docker binary (such as that provided by https://get.docker.com), you give the container the full access to create and manipulate the host's Docker daemon.

$ docker run -p 127.0.0.1:80:8080 ubuntu bash

This binds port 8080 of the container to port 80 on 127.0.0.1 of the host machine. The Docker User Guide explains in detail how to manipulate ports in Docker.

$ docker run --expose 80 ubuntu bash

This exposes port 80 of the container for use within a link without publishing the port to the host system's interfaces. The Docker User Guide explains in detail how to manipulate ports in Docker.

$ docker run -e MYVAR1 --env MYVAR2=foo --env-file ./env.list ubuntu bash

This sets environmental variables in the container. For illustration all three flags are shown here. Where -e, --env take an environment variable and value, or if no = is provided, then that variable's current value is passed through (i.e. $MYVAR1 from the host is set to $MYVAR1 in the container). When no = is provided and that variable is not defined in the client's environment then that variable will be removed from the container's list of environment variables. All three flags, -e, --env and --env-file can be repeated.

Regardless of the order of these three flags, the --env-file are processed first, and then -e, --env flags. This way, the -e or --env will override variables as needed.

$ cat ./env.list
TEST_FOO=BAR
$ docker run --env TEST_FOO="This is a test" --env-file ./env.list busybox env | grep TEST_FOO
TEST_FOO=This is a test

The --env-file flag takes a filename as an argument and expects each line to be in the VAR=VAL format, mimicking the argument passed to --env. Comment lines need only be prefixed with #

An example of a file passed with --env-file

$ cat ./env.list
TEST_FOO=BAR

# this is a comment
TEST_APP_DEST_HOST=10.10.0.127
TEST_APP_DEST_PORT=8888
_TEST_BAR=FOO
TEST_APP_42=magic
helloWorld=true
# 123qwe=bar <- is not valid

# pass through this variable from the caller
TEST_PASSTHROUGH
$ TEST_PASSTHROUGH=howdy docker run --env-file ./env.list busybox env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=5198e0745561
TEST_FOO=BAR
TEST_APP_DEST_HOST=10.10.0.127
TEST_APP_DEST_PORT=8888
_TEST_BAR=FOO
TEST_APP_42=magic
helloWorld=true
TEST_PASSTHROUGH=howdy
HOME=/root

$ docker run --env-file ./env.list busybox env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=5198e0745561
TEST_FOO=BAR
TEST_APP_DEST_HOST=10.10.0.127
TEST_APP_DEST_PORT=8888
_TEST_BAR=FOO
TEST_APP_42=magic
helloWorld=true
TEST_PASSTHROUGH=
HOME=/root

Note: Environment variables names must consist solely of letters, numbers, and underscores - and cannot start with a number.

A label is a a key=value pair that applies metadata to a container. To label a container with two labels:

$ docker run -l my-label --label com.example.foo=bar ubuntu bash

The my-label key doesn't specify a value so the label defaults to an empty string(""). To add multiple labels, repeat the label flag (-l or --label).

The key=value must be unique to avoid overwriting the label value. If you specify labels with identical keys but different values, each subsequent value overwrites the previous. Docker uses the last key=value you supply.

Use the --label-file flag to load multiple labels from a file. Delimit each label in the file with an EOL mark. The example below loads labels from a labels file in the current directory:

$ docker run --label-file ./labels ubuntu bash

The label-file format is similar to the format for loading environment variables. (Unlike environment variables, labels are not visible to processes running inside a container.) The following example illustrates a label-file format:

com.example.label1="a label"

# this is a comment
com.example.label2=another\ label
com.example.label3

You can load multiple label-files by supplying multiple --label-file flags.

For additional information on working with labels, see Labels - custom metadata in Docker in the Docker User Guide.

$ docker run --link /redis:redis --name console ubuntu bash

The --link flag will link the container named /redis into the newly created container with the alias redis. The new container can access the network and environment of the redis container via environment variables. The --link flag will also just accept the form <name or id> in which case the alias will match the name. For instance, you could have written the previous example as:

$ docker run --link redis --name console ubuntu bash

The --name flag will assign the name console to the newly created container.

$ docker run --volumes-from 777f7dc92da7 --volumes-from ba8c0c54f0f2:ro -i -t ubuntu pwd

The --volumes-from flag mounts all the defined volumes from the referenced containers. Containers can be specified by repetitions of the --volumes-from argument. The container ID may be optionally suffixed with :ro or :rw to mount the volumes in read-only or read-write mode, respectively. By default, the volumes are mounted in the same mode (read write or read only) as the reference container.

Labeling systems like SELinux require that proper labels are placed on volume content mounted into a container. Without a label, the security system might prevent the processes running inside the container from using the content. By default, Docker does not change the labels set by the OS.

To change the label in the container context, you can add either of two suffixes :z or :Z to the volume mount. These suffixes tell Docker to relabel file objects on the shared volumes. The z option tells Docker that two containers share the volume content. As a result, Docker labels the content with a shared content label. Shared volume labels allow all containers to read/write content. The Z option tells Docker to label the content with a private unshared label. Only the current container can use a private volume.

The -a flag tells docker run to bind to the container's STDIN, STDOUT or STDERR. This makes it possible to manipulate the output and input as needed.

$ echo "test" | docker run -i -a stdin ubuntu cat -

This pipes data into a container and prints the container's ID by attaching only to the container's STDIN.

$ docker run -a stderr ubuntu echo test

This isn't going to print anything unless there's an error because we've only attached to the STDERR of the container. The container's logs still store what's been written to STDERR and STDOUT.

$ cat somefile | docker run -i -a stdin mybuilder dobuild

This is how piping a file into a container could be done for a build. The container's ID will be printed after the build is done and the build logs could be retrieved using docker logs. This is useful if you need to pipe a file or something else into a container and retrieve the container's ID once the container has finished running.

$ docker run --device=/dev/sdc:/dev/xvdc --device=/dev/sdd --device=/dev/zero:/dev/nulo -i -t ubuntu ls -l /dev/{xvdc,sdd,nulo}
brw-rw---- 1 root disk 8, 2 Feb  9 16:05 /dev/xvdc
brw-rw---- 1 root disk 8, 3 Feb  9 16:05 /dev/sdd
crw-rw-rw- 1 root root 1, 5 Feb  9 16:05 /dev/nulo

It is often necessary to directly expose devices to a container. The --device option enables that. For example, a specific block storage device or loop device or audio device can be added to an otherwise unprivileged container (without the --privileged flag) and have the application directly access it.

By default, the container will be able to read, write and mknod these devices. This can be overridden using a third :rwm set of options to each --device flag:

$ docker run --device=/dev/sda:/dev/xvdc --rm -it ubuntu fdisk  /dev/xvdc

Command (m for help): q
$ docker run --device=/dev/sda:/dev/xvdc:ro --rm -it ubuntu fdisk  /dev/xvdc
You will not be able to write the partition table.

Command (m for help): q

$ docker run --device=/dev/sda:/dev/xvdc --rm -it ubuntu fdisk  /dev/xvdc

Command (m for help): q

$ docker run --device=/dev/sda:/dev/xvdc:m --rm -it ubuntu fdisk  /dev/xvdc
fdisk: unable to open /dev/xvdc: Operation not permitted

Note: --device cannot be safely used with ephemeral devices. Block devices that may be removed should not be added to untrusted containers with --device.

A complete example:

$ docker run -d --name static static-web-files sh
$ docker run -d --expose=8098 --name riak riakserver
$ docker run -d -m 100m -e DEVELOPMENT=1 -e BRANCH=example-code -v $(pwd):/app/bin:ro --name app appserver
$ docker run -d -p 1443:443 --dns=10.0.0.1 --dns-search=dev.org -v /var/log/httpd --volumes-from static --link riak --link app -h www.sven.dev.org --name web webserver
$ docker run -t -i --rm --volumes-from web -w /var/log/httpd busybox tail -f access.log

This example shows five containers that might be set up to test a web application change:

1. Start a pre-prepared volume image static-web-files (in the background) that has CSS, image and static HTML in it, (with a VOLUME instruction in the Dockerfile to allow the web server to use those files);
2. Start a pre-prepared riakserver image, give the container name riak and expose port 8098 to any containers that link to it;
3. Start the appserver image, restricting its memory usage to 100MB, setting two environment variables DEVELOPMENT and BRANCH and bind-mounting the current directory ($(pwd)) in the container in read-only mode as /app/bin;
4. Start the webserver, mapping port 443 in the container to port 1443 on the Docker server, setting the DNS server to 10.0.0.1 and DNS search domain to dev.org, creating a volume to put the log files into (so we can access it from another container), then importing the files from the volume exposed by the static container, and linking to all exposed ports from riak and app. Lastly, we set the hostname to web.sven.dev.org so its consistent with the pre-generated SSL certificate;
5. Finally, we create a container that runs tail -f access.log using the logs volume from the web container, setting the workdir to /var/log/httpd. The --rm option means that when the container exits, the container's layer is removed.

Restart policies

Use Docker's --restart to specify a container's restart policy. A restart policy controls whether the Docker daemon restarts a container after exit. Docker supports the following restart policies:

Policy	Result
no	Do not automatically restart the container when it exits. This is the default.
on-failure[:max-retries]	Restart only if the container exits with a non-zero exit status. Optionally, limit the number of restart retries the Docker daemon attempts.
always	Always restart the container regardless of the exit status. When you specify always, the Docker daemon will try to restart the container indefinitely.

$ docker run --restart=always redis

This will run the redis container with a restart policy of always so that if the container exits, Docker will restart it.

More detailed information on restart policies can be found in the Restart Policies (--restart) section of the Docker run reference page.

Adding entries to a container hosts file

You can add other hosts into a container's /etc/hosts file by using one or more --add-host flags. This example adds a static address for a host named docker:

$ docker run --add-host=docker:10.180.0.1 --rm -it debian
$$ ping docker
PING docker (10.180.0.1): 48 data bytes
56 bytes from 10.180.0.1: icmp_seq=0 ttl=254 time=7.600 ms
56 bytes from 10.180.0.1: icmp_seq=1 ttl=254 time=30.705 ms
^C--- docker ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 7.600/19.152/30.705/11.553 ms

Sometimes you need to connect to the Docker host from within your container. To enable this, pass the Docker host's IP address to the container using the --add-host flag. To find the host's address, use the ip addr show command.

The flags you pass to ip addr show depend on whether you are using IPv4 or IPv6 networking in your containers. Use the following flags for IPv4 address retrieval for a network device named eth0:

$ HOSTIP=`ip -4 addr show scope global dev eth0 | grep inet | awk '{print \$2}' | cut -d / -f 1`
$ docker run  --add-host=docker:${HOSTIP} --rm -it debian

For IPv6 use the -6 flag instead of the -4 flag. For other network devices, replace eth0 with the correct device name (for example docker0 for the bridge device).

Setting ulimits in a container

Since setting ulimit settings in a container requires extra privileges not available in the default container, you can set these using the --ulimit flag. --ulimit is specified with a soft and hard limit as such: <type>=<soft limit>[:<hard limit>], for example:

$ docker run --ulimit nofile=1024:1024 --rm debian ulimit -n
1024

Note: If you do not provide a hard limit, the soft limit will be used for both values. If no ulimits are set, they will be inherited from the default ulimits set on the daemon. as option is disabled now. In other words, the following script is not supported: $ docker run -it --ulimit as=1024 fedora /bin/bash

The values are sent to the appropriate syscall as they are set. Docker doesn't perform any byte conversion. Take this into account when setting the values.

For nproc usage:

Be careful setting nproc with the ulimit flag as nproc is designed by Linux to set the maximum number of processes available to a user, not to a container. For example, start four containers with daemon user:

docker run -d -u daemon --ulimit nproc=3 busybox top
docker run -d -u daemon --ulimit nproc=3 busybox top
docker run -d -u daemon --ulimit nproc=3 busybox top
docker run -d -u daemon --ulimit nproc=3 busybox top

The 4th container fails and reports "[8] System error: resource temporarily unavailable" error. This fails because the caller set nproc=3 resulting in the first three containers using up the three processes quota set for the daemon user.