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https://docs.docker.com/engine/reference/commandline/run/#/configure-namespaced-kernel-parameters-sysctls-at-runtime

Run a command in a new container

Usage

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

Refer to the options section for an overview of available OPTIONS for this command.

Description

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.

For information on connecting a container to a network, see the “Docker network overview”.

For example uses of this command, refer to the examples section below.

Options

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, --workdir)

$ 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 (--storage-opt)

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

This (size) will allow to set the container filesystem 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 filesystem is xfs and mounted with the pquota mount option. Under these conditions, user can pass any size less than the backing filesystem 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

Add bind mounts or volumes using the --mount flag

The --mount flag allows you to mount volumes, host-directories and tmpfs mounts in a container.

The --mount flag supports most options that are supported by the -v or the --volume flag, but uses a different syntax. For in-depth information on the --mount flag, and a comparison between --volume and --mount, refer to Bind mounts.

Even though there is no plan to deprecate --volume, usage of --mount is recommended.

Examples:

$ docker run --read-only --mount type=volume,target=/icanwrite busybox touch /icanwrite/here

$ docker run -t -i --mount type=bind,src=/data,dst=/data busybox sh

Publish or expose port (-p, --expose)

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

This binds port 8080 of the container to TCP port 80 on 127.0.0.1 of the host machine. You can also specify udp and sctp ports. The Docker User Guide explains in detail how to manipulate ports in Docker.

Note that ports which are not bound to the host (i.e., -p 80:80 instead of -p 127.0.0.1:80:80) will be accessible from the outside. This also applies if you configured UFW to block this specific port, as Docker manages its own iptables rules. Read more

$ docker run --expose 80 ubuntu bash

This exposes port 80 of the container without publishing the port to the host system’s interfaces.

Set the pull policy (--pull)

Use the --pull flag to set the image pull policy when creating (and running) the container.

The --pull flag can take one of these values:

When creating (and running) a container from an image, the daemon checks if the image exists in the local image cache. If the image is missing, an error is returned to the CLI, allowing it to initiate a pull.

The default (missing) is to only pull the image if it is not present in the daemon’s image cache. This default allows you to run images that only exist locally (for example, images you built from a Dockerfile, but that have not been pushed to a registry), and reduces networking.

The always option always initiates a pull before creating the container. This option makes sure the image is up-to-date, and prevents you from using outdated images, but may not be suitable in situations where you want to test a locally built image before pushing (as pulling the image overwrites the existing image in the image cache).

The never option disables (implicit) pulling images when creating containers, and only uses images that are available in the image cache. If the specified image is not found, an error is produced, and the container is not created. This option is useful in situations where networking is not available, or to prevent images from being pulled implicitly when creating containers.

The following example shows docker run with the --pull=never option set, which produces en error as the image is missing in the image-cache:

$ docker run --pull=never hello-world
docker: Error response from daemon: No such image: hello-world:latest.

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

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

Use the -e, --env, and --env-file flags to set simple (non-array) environment variables in the container you’re running, or overwrite variables that are defined in the Dockerfile of the image you’re running.

You can define the variable and its value when running the container:

$ docker run --env VAR1=value1 --env VAR2=value2 ubuntu env | grep VAR
VAR1=value1
VAR2=value2

You can also use variables that you’ve exported to your local environment:

export VAR1=value1
export VAR2=value2

$ docker run --env VAR1 --env VAR2 ubuntu env | grep VAR
VAR1=value1
VAR2=value2

When running the command, the Docker CLI client checks the value the variable has in your local environment and passes it to the container. If no = is provided and that variable is not exported in your local environment, the variable won’t be set in the container.

You can also load the environment variables from a file. This file should use the syntax <variable>=value (which sets the variable to the given value) or <variable> (which takes the value from the local environment), and # for comments.

$ cat env.list
# This is a comment
VAR1=value1
VAR2=value2
USER

$ docker run --env-file env.list ubuntu env | grep -E 'VAR|USER'
VAR1=value1
VAR2=value2
USER=jonzeolla

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. The following commands create a network named my-net, and adds a busybox container to the my-net network.

$ docker network create my-net
$ 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 using 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

The default bridge network only allow containers to communicate with each other using internal IP addresses. User-created bridge networks provide DNS resolution between containers using container names.

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, --attach)

The --attach (or -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 a way of using --attach to pipe a build file into a container. 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.

See also the docker cp command.

Add host device to container (--device)

$ docker run -it --rm \
    --device=/dev/sdc:/dev/xvdc \
    --device=/dev/sdd \
    --device=/dev/zero:/dev/foobar \
    ubuntu ls -l /dev/{xvdc,sdd,foobar}

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/foobar

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. If the container is running in privileged mode, then the permissions specified will be ignored.

$ 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

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

For Windows, the format of the string passed to the --device option is in the form of --device=<IdType>/<Id>. Beginning with Windows Server 2019 and Windows 10 October 2018 Update, Windows only supports an IdType of class and the Id as a device interface class GUID. Refer to the table defined in the Windows container docs for a list of container-supported device interface class GUIDs.

If this option is specified for a process-isolated Windows container, all devices that implement the requested device interface class GUID are made available in the container. For example, the command below makes all COM ports on the host visible in the container.

PS C:\> docker run --device=class/86E0D1E0-8089-11D0-9CE4-08003E301F73 mcr.microsoft.com/windows/servercore:ltsc2019

Note

The --device option is only supported on process-isolated Windows containers. This option fails if the container isolation is hyperv or when running Linux Containers on Windows (LCOW).

Using 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 solutions 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 run -d --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 docker run / docker create command.

Access an NVIDIA GPU

The --gpus flag allows you to access NVIDIA GPU resources. First you need to install nvidia-container-runtime. Visit Specify a container’s resources for more information.

To use --gpus, specify which GPUs (or all) to use. If no value is provided, all available GPUs are used. The example below exposes all available GPUs.

$ docker run -it --rm --gpus all ubuntu nvidia-smi

Use the device option to specify GPUs. The example below exposes a specific GPU.

$ docker run -it --rm --gpus device=GPU-3a23c669-1f69-c64e-cf85-44e9b07e7a2a ubuntu nvidia-smi

The example below exposes the first and third GPUs.

$ docker run -it --rm --gpus '"device=0,2"' nvidia-smi

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:93.184.216.34 --rm -it alpine

/ # ping docker
PING docker (93.184.216.34): 56 data bytes
64 bytes from 93.184.216.34: seq=0 ttl=37 time=93.052 ms
64 bytes from 93.184.216.34: seq=1 ttl=37 time=92.467 ms
64 bytes from 93.184.216.34: seq=2 ttl=37 time=92.252 ms
^C
--- docker ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 92.209/92.495/93.052 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 | sed -n 1p`
$ 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 is used for both values. If no ulimits are set, they are inherited from the default ulimits set on the daemon. The 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 signal name in the format SIG<NAME>, for instance SIGKILL, or an unsigned number that matches a position in the kernel’s syscall table, for instance 9.

The default is SIGTERM if not specified.

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 number of seconds to wait for the container to stop after sending the pre-defined (see --stop-signal) system call signal. If the container does not exit after the timeout elapses, it is forcibly killed with a SIGKILL signal.

If --stop-timeout is set to -1, no timeout is applied, and the daemon will wait indefinitely for the container to exit.

The default is determined by the daemon, and is 10 seconds for Linux containers, and 30 seconds for Windows containers.

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, and hyperv on Windows client operating systems, such as Windows 10. Process isolation has better performance, but requires that the image and host use the same kernel version.

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

Specify hard limits on memory available to containers (-m, --memory)

These parameters always set an upper limit on the memory available to the container. On Linux, this is set on the cgroup and applications in a container can query it at /sys/fs/cgroup/memory/memory.limit_in_bytes.

On Windows, this will affect containers differently depending on what type of isolation is used.

• With process isolation, Windows will report the full memory of the host system, not the limit to applications running inside the container

    PS C:\> docker run -it -m 2GB --isolation=process microsoft/nanoserver powershell Get-ComputerInfo *memory*
  
    CsTotalPhysicalMemory      : 17064509440
    CsPhyicallyInstalledMemory : 16777216
    OsTotalVisibleMemorySize   : 16664560
    OsFreePhysicalMemory       : 14646720
    OsTotalVirtualMemorySize   : 19154928
    OsFreeVirtualMemory        : 17197440
    OsInUseVirtualMemory       : 1957488
    OsMaxProcessMemorySize     : 137438953344

• With hyperv isolation, Windows will create a utility VM that is big enough to hold the memory limit, plus the minimal OS needed to host the container. That size is reported as “Total Physical Memory.”

    PS C:\> docker run -it -m 2GB --isolation=hyperv microsoft/nanoserver powershell Get-ComputerInfo *memory*
  
    CsTotalPhysicalMemory      : 2683355136
    CsPhyicallyInstalledMemory :
    OsTotalVisibleMemorySize   : 2620464
    OsFreePhysicalMemory       : 2306552
    OsTotalVirtualMemorySize   : 2620464
    OsFreeVirtualMemory        : 2356692
    OsInUseVirtualMemory       : 263772
    OsMaxProcessMemorySize     : 137438953344

Configure namespaced kernel parameters (sysctls) at runtime (--sysctl)

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 are not allowed.

Network Namespace:

• Sysctls beginning with net.*
• If you use the --network=host option using these sysctls are not allowed.