• Docker E Flag
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Description

Run a command in a new container

$ sudo docker ps; This lists running containers $ sudo docker ps -a; The -a flag will list all containers, both running and stopped. $ sudo docker ps -l; The -l flag lists the last run container even if it is stopped. Starting a stopped container $ sudo docker start containername; containername can be obtained from the docker ps -a listing. Stopping a daemonized container. Step 1 – Run a container without the privileged option using the command shown below: – docker run -it -rm DockerImage sh docker run -it -rm ubuntu sh. In the above snapshot, we can see that a container has been started using the ‘ubuntu’ Docker image and connected to the container.

Docker run -ti -name containername imagename /command: Start a container: docker start containername: Stop a container: docker stop containername: Run a command inside a container from the image and remove the container when command is done. Docker run -rm -ti imagename /command: Run a shell command in the container. Docker exec -ti containername 'cmd'. Setting environment variables and run a container docker run -e SETTINGS=development -name mycontainer dockerhubacct/publish:sometag docker run -network=host -name mycontainer dockerhubacct/publish:sometag. Run container using the Host network. The port mappings will be disregarded when the container is running using Host network.

Usage

Extended description

The docker run command first creates a writeable container layer over thespecified 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 itsprevious changes intact using docker start. See docker ps -a to view a listof all containers.

The docker run command can be used in combination with docker commit tochange the command that a container runs. There is additional detailed information about docker run in the Docker run reference.

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)

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

Capture container ID (--cidfile)

This will create a container and print test to the console. The cidfileflag 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 thisfile when docker run exits.

Full container capabilities (--privileged)

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

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

Set working directory (-w)

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

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 thebacking fs is xfs and mounted with the pquota mount option.Under these conditions, user can pass any size less than the backing fs size.

Mount tmpfs (--tmpfs)

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

Mount volume (-v, --read-only)

The -v flag mounts the current working directory into the container. The -wlets the command being executed inside the current working directory, bychanging into the directory to the value returned by pwd. So thiscombination executes the command using the container, but inside thecurrent working directory.

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

Volumes can be used in combination with --read-only to control wherea container writes files. The --read-only flag mounts the container’s rootfilesystem as read only prohibiting writes to locations other than thespecified volumes for the container.

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

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

The following examples will fail when using Windows-based containers, as thedestination 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 sourceof a bind mount must be a local directory, not a file.

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 tmpfsmounts 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 tothe service create command reference.

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

Examples:

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

This binds port 8080 of the container to TCP port 80 on 127.0.0.1 of the hostmachine. You can also specify udp and sctp ports.The Docker User Guideexplains 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 ifyou configured UFW to block this specific port, as Docker manages hisown iptables rules. Read more

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

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

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

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

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

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

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

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:

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

Docker E Flag

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

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

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

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

For additional information on working with labels, see Labels - custommetadata in Docker inthe 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.

You can also choose the IP addresses for the container with --ip and --ip6flags when you start the container on a user-defined network.

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, thecontainers can communicate easily need only another container’s IP addressor name. For overlay networks or custom plugins that support multi-hostconnectivity, containers connected to the same multi-host network but launchedfrom different Engines can also communicate in this way.

Note

Service discovery is unavailable on the default bridge network. Containers cancommunicate via their IP addresses by default. To communicate by name, theymust be linked.

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

Mount volumes from container (--volumes-from)

The --volumes-from flag mounts all the defined volumes from the referencedcontainers. Containers can be specified by repetitions of the --volumes-fromargument. The container ID may be optionally suffixed with :ro or :rw tomount 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) asthe reference container.

Labeling systems like SELinux require that proper labels are placed on volumecontent mounted into a container. Without a label, the security system mightprevent the processes running inside the container from using the content. Bydefault, 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 fileobjects on the shared volumes. The z option tells Docker that two containersshare the volume content. As a result, Docker labels the content with a sharedcontent 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, STDOUTor STDERR. This makes it possible to manipulate the output and input asneeded.

This pipes data into a container and prints the container’s ID by attachingonly to the container’s STDIN.

This isn’t going to print anything unless there’s an error because we’veonly attached to the STDERR of the container. The container’s logsstill store what’s been written to STDERR and STDOUT.

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 buildlogs could be retrieved using docker logs. This isuseful if you need to pipe a file or something else into a container andretrieve the container’s ID once the container has finished running.

Add host device to container (--device)

It is often necessary to directly expose devices to a container. The --deviceoption enables that. For example, a specific block storage device or loopdevice 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 --deviceflag. If the container is running in privileged mode, then the permissions specifiedwill be ignored.

Note

The --device option cannot be safely used with ephemeral devices. Block devicesthat 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 inthe form of --device=<IdType>/<Id>. Beginning with Windows Server 2019and Windows 10 October 2018 Update, Windows only supports an IdType ofclass and the Id as a device interface classGUID.Refer to the table defined in the Windows containerdocsfor a list of container-supported device interface class GUIDs.

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

Note

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

Access an NVIDIA GPU

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

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

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

The example below exposes the first and third GPUs.

Restart policies (--restart)

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

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

More detailed information on restart policies can be found in theRestart 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 ormore --add-host flags. This example adds a static address for a host nameddocker:

Sometimes you need to connect to the Docker host from within yourcontainer. To enable this, pass the Docker host’s IP address tothe 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 areusing IPv4 or IPv6 networking in your containers. Use the followingflags for IPv4 address retrieval for a network device named eth0:

For IPv6 use the -6 flag instead of the -4 flag. For other networkdevices, replace eth0 with the correct device name (for example docker0for the bridge device).

Set ulimits in container (--ulimit)

Since setting ulimit settings in a container requires extra privileges notavailable 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 Flags Cheat Sheet Template

Note

If you do not provide a hard limit, the soft limit is usedfor both values. If no ulimits are set, they are inherited fromthe default ulimits set on the daemon. The as option is disabled now.In other words, the following script is not supported:

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 themaximum number of processes available to a user, not to a container. For example, start fourcontainers with daemon user:

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 upthe 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 callsignal 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 onWindows. The --isolation <value> option sets a container’s isolation technology.On Linux, the only supported is the default option which usesLinux namespaces. These two commands are equivalent on Linux:

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

The default isolation on Windows server operating systems is process. The defaultisolation on Windows client operating systems is hyperv. An attempt to start a container on a clientoperating system older than Windows 10 1809 with --isolation process will fail.

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

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

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, thisis 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

• 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.”

Configure namespaced kernel parameters (sysctls) at runtime

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

Note

Not all sysctls are namespaced. Docker does not support changing sysctlsinside of a container that also modify the host system. As the kernelevolves 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.

Parent command

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