docker run

Description

Run a command in a new container

Usage

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

Options

Parent command

Examples

Assign name and allocate pseudo-TTY (–name, -it)

$ 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.

Capture container ID (–cidfile)

$ 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.

Full container capabilities (–privileged)

$ 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 -t -i --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.

Set working directory (-w)

$ 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 exist it is created inside the container.

Set storage driver options per container

$ docker run -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 then the backing fs size.

Mount tmpfs (–tmpfs)

$ docker run -d --tmpfs /run:rw,noexec,nosuid,size=65536k my_image

The --tmpfs flag mounts an empty tmpfs into the container with the rw, noexec, nosuid, size=65536k options.

Mount volume (-v, –read-only)

$ 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 /path/to/static-docker-binary:/usr/bin/docker busybox sh

By bind-mounting the docker unix socket and statically linked docker binary (refer to get the linux binary), you give the container the full access to create and manipulate the host’s Docker daemon.

On Windows, the paths must be specified using Windows-style semantics.

PS C:\> docker run -v c:\foo:c:\dest microsoft/nanoserver cmd /s /c type c:\dest\somefile.txt
Contents of file

PS C:\> docker run -v c:\foo:d: microsoft/nanoserver cmd /s /c type d:\somefile.txt
Contents of file

The following examples will fail when using Windows-based containers, as the destination of a volume or bind-mount inside the container must be one of: a non-existing or empty directory; or a drive other than C:. Further, the source of a bind mount must be a local directory, not a file.

net use z: \\remotemachine\share
docker run -v z:\foo:c:\dest ...
docker run -v \\uncpath\to\directory:c:\dest ...
docker run -v c:\foo\somefile.txt:c:\dest ...
docker run -v c:\foo:c: ...
docker run -v c:\foo:c:\existing-directory-with-contents ...

For in-depth information about volumes, refer to manage data in containers

Publish or expose port (-p, –expose)

$ 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 without publishing the port to the host system’s interfaces.

Set environment variables (-e, –env, –env-file)

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

This sets simple (non-array) 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, set via export, 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
org.spring.config=something

# 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
123qwe=bar
org.spring.config=something

$ 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
123qwe=bar
org.spring.config=something

Set metadata on container (-l, –label, –label-file)

A label is 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.

Connect a container to a network (–network)

When you start a container use the --network flag to connect it to a network. This adds the busybox container to the my-net network.

$ docker run -itd --network=my-net busybox

You can also choose the IP addresses for the container with --ip and --ip6 flags when you start the container on a user-defined network.

$ docker run -itd --network=my-net --ip=10.10.9.75 busybox

If you want to add a running container to a network use the docker network connect subcommand.

You can connect multiple containers to the same network. Once connected, the containers can communicate easily need only another container’s IP address or name. For overlay networks or custom plugins that support multi-host connectivity, containers connected to the same multi-host network but launched from different Engines can also communicate in this way.

Note: Service discovery is unavailable on the default bridge network. Containers can communicate via their IP addresses by default. To communicate by name, they must be linked.

You can disconnect a container from a network using the docker network disconnect command.

Mount volumes from container (–volumes-from)

$ 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.

Attach to STDIN/STDOUT/STDERR (-a)

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.

Add host device to container (–device)

$ 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:r --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:rw --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.

Restart policies (–restart)

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:

$ 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.

Add entries to container hosts file (–add-host)

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
root@f38c87f2a42d:/# 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).

Set ulimits in container (–ulimit)

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 sh -c "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.

Stop container with signal (–stop-signal)

The --stop-signal flag sets the system call signal that will be sent to the container to exit. This signal can be a valid unsigned number that matches a position in the kernel’s syscall table, for instance 9, or a signal name in the format SIGNAME, for instance SIGKILL.

Optional security options (–security-opt)

On Windows, this flag can be used to specify the credentialspec option. The credentialspec must be in the format file://spec.txt or registry://keyname.

Stop container with timeout (–stop-timeout)

The --stop-timeout flag sets the timeout (in seconds) that a pre-defined (see --stop-signal) system call signal that will be sent to the container to exit. After timeout elapses the container will be killed with SIGKILL.

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. These two commands are equivalent on Linux:

$ docker run -d busybox top
$ docker run -d --isolation default busybox top

On Windows, --isolation can take one of these values:

The default isolation on Windows server operating systems is process. The default (and only supported) isolation on Windows client operating systems is hyperv. An attempt to start a container on a client operating system with --isolation process will fail.

On Windows server, assuming the default configuration, these commands are equivalent and result in process isolation:

PS C:\> docker run -d microsoft/nanoserver powershell echo process
PS C:\> docker run -d --isolation default microsoft/nanoserver powershell echo process
PS C:\> docker run -d --isolation process microsoft/nanoserver powershell echo process

If you have set the --exec-opt isolation=hyperv option on the Docker daemon, or are running against a Windows client-based daemon, these commands are equivalent and result in hyperv isolation:

PS C:\> docker run -d microsoft/nanoserver powershell echo hyperv
PS C:\> docker run -d --isolation default microsoft/nanoserver powershell echo hyperv
PS C:\> docker run -d --isolation hyperv microsoft/nanoserver powershell echo hyperv

Configure namespaced kernel parameters (sysctls) at runtime

The --sysctl sets namespaced kernel parameters (sysctls) in the container. For example, to turn on IP forwarding in the containers network namespace, run this command:

$ docker run --sysctl net.ipv4.ip_forward=1 someimage

Note: Not all sysctls are namespaced. Docker does not support changing sysctls inside of a container that also modify the host system. As the kernel evolves we expect to see more sysctls become namespaced.

Currently supported sysctls

IPC Namespace:

kernel.msgmax, kernel.msgmnb, kernel.msgmni, kernel.sem, kernel.shmall, kernel.shmmax, kernel.shmmni, kernel.shm_rmid_forced Sysctls beginning with fs.mqueue.*

If you use the --ipc=host option these sysctls will not be allowed.

Network Namespace: Sysctls beginning with net.*

If you use the --network=host option using these sysctls will not be allowed.

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