22 KiB
% DOCKER(1) Docker User Manuals % Docker Community % JUNE 2014
NAME
docker-run - Run a command in a new container
SYNOPSIS
docker run [-a|--attach[=[]]] [--add-host[=[]]] [-c|--cpu-shares[=0]] [--cap-add[=[]]] [--cap-drop[=[]]] [--cidfile[=CIDFILE]] [--cpuset[=CPUSET]] [-d|--detach[=false]] [--device[=[]]] [--dns-search[=[]]] [--dns[=[]]] [-e|--env[=[]]] [--entrypoint[=ENTRYPOINT]] [--env-file[=[]]] [--expose[=[]]] [-h|--hostname[=HOSTNAME]] [--help] [-i|--interactive[=false]] [--ipc[=IPC]] [--link[=[]]] [--lxc-conf[=[]]] [-m|--memory[=MEMORY]] [--memory-swap[=MEMORY-SWAP]] [--mac-address[=MAC-ADDRESS]] [--name[=NAME]] [--net[="bridge"]] [-P|--publish-all[=false]] [-p|--publish[=[]]] [--pid[=[]]] [--privileged[=false]] [--read-only[=false]] [--restart[=RESTART]] [--rm[=false]] [--security-opt[=[]]] [--sig-proxy[=true]] [-t|--tty[=false]] [-u|--user[=USER]] [-v|--volume[=[]]] [--volumes-from[=[]*]] [-w|--workdir[=WORKDIR]] IMAGE [COMMAND] [ARG...]
DESCRIPTION
Run a process in a new container. docker run starts a process with its own file system, its own networking, and its own isolated process tree. The IMAGE which starts the process may define defaults related to the process that will be run in the container, the networking to expose, and more, but docker run gives final control to the operator or administrator who starts the container from the image. For that reason docker run has more options than any other Docker command.
If the IMAGE is not already loaded then docker run will pull the IMAGE, and all image dependencies, from the repository in the same way running docker pull IMAGE, before it starts the container from that image.
OPTIONS
-a, --attach=[] Attach to STDIN, STDOUT or STDERR.
In foreground mode (the default when -d is not specified), docker run can start the process in the container and attach the console to the process’s standard input, output, and standard error. It can even pretend to be a TTY (this is what most commandline executables expect) and pass along signals. The -a option can be set for each of stdin, stdout, and stderr.
--add-host=[] Add a custom host-to-IP mapping (host:ip)
Add a line to /etc/hosts. The format is hostname:ip. The --add-host option can be set multiple times.
-c, --cpu-shares=0 CPU shares (relative weight)
You can increase the priority of a container with the -c option. By default, all containers run at the same priority and get the same proportion of CPU cycles, but you can tell the kernel to give more shares of CPU time to one or more containers when you start them via docker run.
The flag -c or --cpu-shares with value 0 indicates that the running
container has access to all 1024 (default) CPU shares. However, this value
can be modified to run a container with a different priority or different
proportion of CPU cycles.
E.g., If we start three {C0, C1, C2} containers with default values
(-c OR --cpu-shares = 0) and one {C3} with (-c or --cpu-shares=512)
then C0, C1, and C2 would have access to 100% CPU shares (1024) and C3 would
only have access to 50% CPU shares (512). In the context of a time-sliced OS
with time quantum set as 100 milliseconds, containers C0, C1, and C2 will run
for full-time quantum, and container C3 will run for half-time quantum i.e 50
milliseconds.
--cap-add=[] Add Linux capabilities
--cap-drop=[] Drop Linux capabilities
--cidfile="" Write the container ID to the file
--cpuset="" CPUs in which to allow execution (0-3, 0,1)
-d, --detach=true|false Detached mode: run the container in the background and print the new container ID. The default is false.
At any time you can run docker ps in the other shell to view a list of the running containers. You can reattach to a detached container with docker attach. If you choose to run a container in the detached mode, then you cannot use the -rm option.
When attached in the tty mode, you can detach from a running container without stopping the process by pressing the keys CTRL-P CTRL-Q.
--device=[] Add a host device to the container (e.g. --device=/dev/sdc:/dev/xvdc:rwm)
--dns-search=[] Set custom DNS search domains (Use --dns-search=. if you don't wish to set the search domain)
--dns=[] Set custom DNS servers
This option can be used to override the DNS configuration passed to the container. Typically this is necessary when the host DNS configuration is invalid for the container (e.g., 127.0.0.1). When this is the case the --dns flags is necessary for every run.
-e, --env=[] Set environment variables
This option allows you to specify arbitrary environment variables that are available for the process that will be launched inside of the container.
--entrypoint="" Overwrite the default ENTRYPOINT of the image
This option allows you to overwrite the default entrypoint of the image that is set in the Dockerfile. The ENTRYPOINT of an image is similar to a COMMAND because it specifies what executable to run when the container starts, but it is (purposely) more difficult to override. The ENTRYPOINT gives a container its default nature or behavior, so that when you set an ENTRYPOINT you can run the container as if it were that binary, complete with default options, and you can pass in more options via the COMMAND. But, sometimes an operator may want to run something else inside the container, so you can override the default ENTRYPOINT at runtime by using a --entrypoint and a string to specify the new ENTRYPOINT.
--env-file=[] Read in a line delimited file of environment variables
--expose=[] Expose a port, or a range of ports (e.g. --expose=3300-3310), from the container without publishing it to your host
-h, --hostname="" Container host name
Sets the container host name that is available inside the container.
--help Print usage statement
-i, --interactive=true|false Keep STDIN open even if not attached. The default is false.
When set to true, keep stdin open even if not attached. The default is false.
--ipc="" Default is to create a private IPC namespace (POSIX SysV IPC) for the container 'container:<name|id>': reuses another container shared memory, semaphores and message queues 'host': use the host shared memory,semaphores and message queues inside the container. Note: the host mode gives the container full access to local shared memory and is therefore considered insecure.
--link=[] Add link to another container in the form of :alias
If the operator uses --link when starting the new client container, then the client container can access the exposed port via a private networking interface. Docker will set some environment variables in the client container to help indicate which interface and port to use.
--lxc-conf=[] (lxc exec-driver only) Add custom lxc options --lxc-conf="lxc.cgroup.cpuset.cpus = 0,1"
-m, --memory="" Memory limit (format: , where unit = b, k, m or g)
Allows you to constrain the memory available to a container. If the host supports swap memory, then the -m memory setting can be larger than physical RAM. If a limit of 0 is specified (not using -m), the container's memory is not limited. The actual limit may be rounded up to a multiple of the operating system's page size (the value would be very large, that's millions of trillions).
--memory-swap="" Total memory limit (memory + swap)
Set -1 to disable swap (format: , where unit = b, k, m or g).
This value should always larger than -m, so you should alway use this with -m.
--mac-address="" Container MAC address (e.g. 92:d0:c6:0a:29:33)
Remember that the MAC address in an Ethernet network must be unique. The IPv6 link-local address will be based on the device's MAC address according to RFC4862.
--name="" Assign a name to the container
The operator can identify a container in three ways: UUID long identifier (“f78375b1c487e03c9438c729345e54db9d20cfa2ac1fc3494b6eb60872e74778”) UUID short identifier (“f78375b1c487”) Name (“jonah”)
The UUID identifiers come from the Docker daemon, and if a name is not assigned to the container with --name then the daemon will also generate a random string name. The name is useful when defining links (see --link) (or any other place you need to identify a container). This works for both background and foreground Docker containers.
--net="bridge" Set the Network mode for the container 'bridge': creates a new network stack for the container on the docker bridge 'none': no networking for this container 'container:<name|id>': reuses another container network stack 'host': use the host network stack inside the container. Note: the host mode gives the container full access to local system services such as D-bus and is therefore considered insecure.
-P, --publish-all=true|false Publish all exposed ports to random ports on the host interfaces. The default is false.
When set to true publish all exposed ports to the host interfaces. The default is false. If the operator uses -P (or -p) then Docker will make the exposed port accessible on the host and the ports will be available to any client that can reach the host. When using -P, Docker will bind the exposed ports to a random port on the host between 49153 and 65535. To find the mapping between the host ports and the exposed ports, use docker port.
-p, --publish=[]
Publish a container's port, or range of ports, to the host.
format: ip:hostPort:containerPort | ip::containerPort | hostPort:containerPort | containerPort
Both hostPort and containerPort can be specified as a range of ports.
When specifying ranges for both, the number of container ports in the range must match the number of host ports in the range. (e.g., -p 1234-1236:1234-1236/tcp)
(use 'docker port' to see the actual mapping)
--pid=host Set the PID mode for the container host: use the host's PID namespace inside the container. Note: the host mode gives the container full access to local PID and is therefore considered insecure.
--privileged=true|false Give extended privileges to this container. The default is false.
By default, Docker containers are “unprivileged” (=false) and cannot, for example, run a Docker daemon inside the Docker container. This is because by default a container is not allowed to access any devices. A “privileged” container is given access to all devices.
When the operator executes docker run --privileged, Docker will enable access to all devices on the host as well as set some configuration in AppArmor to allow the container nearly all the same access to the host as processes running outside of a container on the host.
--read-only=true|false Mount the container's root filesystem as read only.
By default a container will have its root filesystem writable allowing processes
to write files anywhere. By specifying the --read-only flag the container will have
its root filesystem mounted as read only prohibiting any writes.
--restart="" Restart policy to apply when a container exits (no, on-failure[:max-retry], always)
--rm=true|false Automatically remove the container when it exits (incompatible with -d). The default is false.
--security-opt=[] Security Options
"label:user:USER" : Set the label user for the container "label:role:ROLE" : Set the label role for the container "label:type:TYPE" : Set the label type for the container "label:level:LEVEL" : Set the label level for the container "label:disable" : Turn off label confinement for the container
--sig-proxy=true|false Proxy received signals to the process (non-TTY mode only). SIGCHLD, SIGSTOP, and SIGKILL are not proxied. The default is true.
-t, --tty=true|false Allocate a pseudo-TTY. The default is false.
When set to true Docker can allocate a pseudo-tty and attach to the standard input of any container. This can be used, for example, to run a throwaway interactive shell. The default is value is false.
The -t option is incompatible with a redirection of the docker client standard input.
-u, --user="" Username or UID
-v, --volume=[] Bind mount a volume (e.g., from the host: -v /host:/container, from Docker: -v /container)
The -v option can be used one or more times to add one or more mounts to a container. These mounts can then be used in other containers using the --volumes-from option.
The volume 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 read-write. See examples.
--volumes-from=[] Mount volumes from the specified container(s)
Will mount volumes from the specified container identified by container-id. Once a volume is mounted in a one container it can be shared with other containers using the --volumes-from option when running those other containers. The volumes can be shared even if the original container with the mount is not running.
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.
-w, --workdir="" Working directory inside the container
The default working directory for running binaries within a container is the root directory (/). The developer can set a different default with the Dockerfile WORKDIR instruction. The operator can override the working directory by using the -w option.
EXAMPLES
Exposing log messages from the container to the host's log
If you want messages that are logged in your container to show up in the host's syslog/journal then you should bind mount the /dev/log directory as follows.
# docker run -v /dev/log:/dev/log -i -t fedora /bin/bash
From inside the container you can test this by sending a message to the log.
(bash)# logger "Hello from my container"
Then exit and check the journal.
# exit
# journalctl -b | grep Hello
This should list the message sent to logger.
Attaching to one or more from STDIN, STDOUT, STDERR
If you do not specify -a then Docker will attach everything (stdin,stdout,stderr) . You can specify to which of the three standard streams (stdin, stdout, stderr) you’d like to connect instead, as in:
# docker run -a stdin -a stdout -i -t fedora /bin/bash
Sharing IPC between containers
Using shm_server.c available here: http://www.cs.cf.ac.uk/Dave/C/node27.html
Testing --ipc=host mode:
Host shows a shared memory segment with 7 pids attached, happens to be from httpd:
$ sudo ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x01128e25 0 root 600 1000 7
Now run a regular container, and it correctly does NOT see the shared memory segment from the host:
$ sudo docker run -it shm ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
Run a container with the new --ipc=host option, and it now sees the shared memory segment from the host httpd:
$ sudo docker run -it --ipc=host shm ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x01128e25 0 root 600 1000 7
Testing --ipc=container:CONTAINERID mode:
Start a container with a program to create a shared memory segment:
sudo docker run -it shm bash
$ sudo shm/shm_server &
$ sudo ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x0000162e 0 root 666 27 1
Create a 2nd container correctly shows no shared memory segment from 1st container:
$ sudo docker run shm ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
Create a 3rd container using the new --ipc=container:CONTAINERID option, now it shows the shared memory segment from the first:
$ sudo docker run -it --ipc=container:ed735b2264ac shm ipcs -m
$ sudo ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x0000162e 0 root 666 27 1
Linking Containers
The link feature allows multiple containers to communicate with each other. For example, a container whose Dockerfile has exposed port 80 can be run and named as follows:
# docker run --name=link-test -d -i -t fedora/httpd
A second container, in this case called linker, can communicate with the httpd container, named link-test, by running with the --link=:
# docker run -t -i --link=link-test:lt --name=linker fedora /bin/bash
Now the container linker is linked to container link-test with the alias lt. Running the env command in the linker container shows environment variables with the LT (alias) context (LT_)
# env
HOSTNAME=668231cb0978
TERM=xterm
LT_PORT_80_TCP=tcp://172.17.0.3:80
LT_PORT_80_TCP_PORT=80
LT_PORT_80_TCP_PROTO=tcp
LT_PORT=tcp://172.17.0.3:80
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
PWD=/
LT_NAME=/linker/lt
SHLVL=1
HOME=/
LT_PORT_80_TCP_ADDR=172.17.0.3
_=/usr/bin/env
When linking two containers Docker will use the exposed ports of the container to create a secure tunnel for the parent to access.
Mapping Ports for External Usage
The exposed port of an application can be mapped to a host port using the -p flag. For example, a httpd port 80 can be mapped to the host port 8080 using the following:
# docker run -p 8080:80 -d -i -t fedora/httpd
Creating and Mounting a Data Volume Container
Many applications require the sharing of persistent data across several containers. Docker allows you to create a Data Volume Container that other containers can mount from. For example, create a named container that contains directories /var/volume1 and /tmp/volume2. The image will need to contain these directories so a couple of RUN mkdir instructions might be required for you fedora-data image:
# docker run --name=data -v /var/volume1 -v /tmp/volume2 -i -t fedora-data true
# docker run --volumes-from=data --name=fedora-container1 -i -t fedora bash
Multiple --volumes-from parameters will bring together multiple data volumes from multiple containers. And it's possible to mount the volumes that came from the DATA container in yet another container via the fedora-container1 intermediary container, allowing to abstract the actual data source from users of that data:
# docker run --volumes-from=fedora-container1 --name=fedora-container2 -i -t fedora bash
Mounting External Volumes
To mount a host directory as a container volume, specify the absolute path to the directory and the absolute path for the container directory separated by a colon:
# docker run -v /var/db:/data1 -i -t fedora bash
When using SELinux, be aware that the host has no knowledge of container SELinux
policy. Therefore, in the above example, if SELinux policy is enforced, the
/var/db directory is not writable to the container. A "Permission Denied"
message will occur and an avc: message in the host's syslog.
To work around this, at time of writing this man page, the following command needs to be run in order for the proper SELinux policy type label to be attached to the host directory:
# chcon -Rt svirt_sandbox_file_t /var/db
Now, writing to the /data1 volume in the container will be allowed and the changes will also be reflected on the host in /var/db.
Using alternative security labeling
You can override the default labeling scheme for each container by specifying
the --security-opt flag. For example, you can specify the MCS/MLS level, a
requirement for MLS systems. Specifying the level in the following command
allows you to share the same content between containers.
# docker run --security-opt label:level:s0:c100,c200 -i -t fedora bash
An MLS example might be:
# docker run --security-opt label:level:TopSecret -i -t rhel7 bash
To disable the security labeling for this container versus running with the
--permissive flag, use the following command:
# docker run --security-opt label:disable -i -t fedora bash
If you want a tighter security policy on the processes within a container, you can specify an alternate type for the container. You could run a container that is only allowed to listen on Apache ports by executing the following command:
# docker run --security-opt label:type:svirt_apache_t -i -t centos bash
Note:
You would have to write policy defining a svirt_apache_t type.
HISTORY
April 2014, Originally compiled by William Henry (whenry at redhat dot com) based on docker.com source material and internal work. June 2014, updated by Sven Dowideit SvenDowideit@home.org.au July 2014, updated by Sven Dowideit SvenDowideit@home.org.au