mirror of
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Signed-off-by: Ma Shimiao <mashimiao.fnst@cn.fujitsu.com>
1349 lines
57 KiB
Markdown
1349 lines
57 KiB
Markdown
<!--[metadata]>
|
||
+++
|
||
title = "Docker run reference"
|
||
description = "Configure containers at runtime"
|
||
keywords = ["docker, run, configure, runtime"]
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||
[menu.main]
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||
parent = "mn_reference"
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||
+++
|
||
<![end-metadata]-->
|
||
|
||
<!-- TODO (@thaJeztah) define more flexible table/td classes -->
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||
<style>
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.content-body table .no-wrap {
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||
white-space: nowrap;
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||
}
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||
</style>
|
||
# Docker run reference
|
||
|
||
Docker runs processes in isolated containers. A container is a process
|
||
which runs on a host. The host may be local or remote. When an operator
|
||
executes `docker run`, the container process that runs is isolated in
|
||
that it has its own file system, its own networking, and its own
|
||
isolated process tree separate from the host.
|
||
|
||
This page details how to use the `docker run` command to define the
|
||
container's resources at runtime.
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||
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||
## General form
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||
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||
The basic `docker run` command takes this form:
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||
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||
$ docker run [OPTIONS] IMAGE[:TAG|@DIGEST] [COMMAND] [ARG...]
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||
|
||
The `docker run` command must specify an [*IMAGE*](glossary.md#image)
|
||
to derive the container from. An image developer can define image
|
||
defaults related to:
|
||
|
||
* detached or foreground running
|
||
* container identification
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||
* network settings
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||
* runtime constraints on CPU and memory
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||
|
||
With the `docker run [OPTIONS]` an operator can add to or override the
|
||
image defaults set by a developer. And, additionally, operators can
|
||
override nearly all the defaults set by the Docker runtime itself. The
|
||
operator's ability to override image and Docker runtime defaults is why
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||
[*run*](commandline/run.md) has more options than any
|
||
other `docker` command.
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||
|
||
To learn how to interpret the types of `[OPTIONS]`, see [*Option
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||
types*](commandline/cli.md#option-types).
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||
|
||
> **Note**: Depending on your Docker system configuration, you may be
|
||
> required to preface the `docker run` command with `sudo`. To avoid
|
||
> having to use `sudo` with the `docker` command, your system
|
||
> administrator can create a Unix group called `docker` and add users to
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||
> it. For more information about this configuration, refer to the Docker
|
||
> installation documentation for your operating system.
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||
|
||
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||
## Operator exclusive options
|
||
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||
Only the operator (the person executing `docker run`) can set the
|
||
following options.
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||
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||
- [Detached vs foreground](#detached-vs-foreground)
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||
- [Detached (-d)](#detached-d)
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||
- [Foreground](#foreground)
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||
- [Container identification](#container-identification)
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||
- [Name (--name)](#name-name)
|
||
- [PID equivalent](#pid-equivalent)
|
||
- [IPC settings (--ipc)](#ipc-settings-ipc)
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||
- [Network settings](#network-settings)
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||
- [Restart policies (--restart)](#restart-policies-restart)
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||
- [Clean up (--rm)](#clean-up-rm)
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||
- [Runtime constraints on resources](#runtime-constraints-on-resources)
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||
- [Runtime privilege and Linux capabilities](#runtime-privilege-and-linux-capabilities)
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||
|
||
## Detached vs foreground
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||
|
||
When starting a Docker container, you must first decide if you want to
|
||
run the container in the background in a "detached" mode or in the
|
||
default foreground mode:
|
||
|
||
-d=false: Detached mode: Run container in the background, print new container id
|
||
|
||
### Detached (-d)
|
||
|
||
To start a container in detached mode, you use `-d=true` or just `-d` option. By
|
||
design, containers started in detached mode exit when the root process used to
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||
run the container exits. A container in detached mode cannot be automatically
|
||
removed when it stops, this means you cannot use the `--rm` option with `-d` option.
|
||
|
||
Do not pass a `service x start` command to a detached container. For example, this
|
||
command attempts to start the `nginx` service.
|
||
|
||
$ docker run -d -p 80:80 my_image service nginx start
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||
|
||
This succeeds in starting the `nginx` service inside the container. However, it
|
||
fails the detached container paradigm in that, the root process (`service nginx
|
||
start`) returns and the detached container stops as designed. As a result, the
|
||
`nginx` service is started but could not be used. Instead, to start a process
|
||
such as the `nginx` web server do the following:
|
||
|
||
$ docker run -d -p 80:80 my_image nginx -g 'daemon off;'
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||
|
||
To do input/output with a detached container use network connections or shared
|
||
volumes. These are required because the container is no longer listening to the
|
||
command line where `docker run` was run.
|
||
|
||
To reattach to a detached container, use `docker`
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||
[*attach*](commandline/attach.md) command.
|
||
|
||
### Foreground
|
||
|
||
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 command line executables expect)
|
||
and pass along signals. All of that is configurable:
|
||
|
||
-a=[] : Attach to `STDIN`, `STDOUT` and/or `STDERR`
|
||
-t=false : Allocate a pseudo-tty
|
||
--sig-proxy=true: Proxy all received signals to the process (non-TTY mode only)
|
||
-i=false : Keep STDIN open even if not attached
|
||
|
||
If you do not specify `-a` then Docker will [attach all standard
|
||
streams]( https://github.com/docker/docker/blob/75a7f4d90cde0295bcfb7213004abce8d4779b75/commands.go#L1797).
|
||
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 ubuntu /bin/bash
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||
|
||
For interactive processes (like a shell), you must use `-i -t` together in
|
||
order to allocate a tty for the container process. `-i -t` is often written `-it`
|
||
as you'll see in later examples. Specifying `-t` is forbidden when the client
|
||
standard output is redirected or piped, such as in:
|
||
`echo test | docker run -i busybox cat`.
|
||
|
||
>**Note**: A process running as PID 1 inside a container is treated
|
||
>specially by Linux: it ignores any signal with the default action.
|
||
>So, the process will not terminate on `SIGINT` or `SIGTERM` unless it is
|
||
>coded to do so.
|
||
|
||
## Container identification
|
||
|
||
### Name (--name)
|
||
|
||
The operator can identify a container in three ways:
|
||
|
||
- UUID long identifier
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||
("f78375b1c487e03c9438c729345e54db9d20cfa2ac1fc3494b6eb60872e74778")
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||
- UUID short identifier ("f78375b1c487")
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||
- Name ("evil_ptolemy")
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||
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||
The UUID identifiers come from the Docker daemon. If you do not assign a
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||
container name with the `--name` option, then the daemon generates a random
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||
string name for you. Defining a `name` can be a handy way to add meaning to a
|
||
container. If you specify a `name`, you can use it when referencing the
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||
container within a Docker network. This works for both background and foreground
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||
Docker containers.
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||
|
||
**Note**: Containers on the default bridge network must be linked to communicate by name.
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||
|
||
### PID equivalent
|
||
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||
Finally, to help with automation, you can have Docker write the
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||
container ID out to a file of your choosing. This is similar to how some
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programs might write out their process ID to a file (you've seen them as
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||
PID files):
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||
|
||
--cidfile="": Write the container ID to the file
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||
|
||
### Image[:tag]
|
||
|
||
While not strictly a means of identifying a container, you can specify a version of an
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||
image you'd like to run the container with by adding `image[:tag]` to the command. For
|
||
example, `docker run ubuntu:14.04`.
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||
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||
### Image[@digest]
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||
|
||
Images using the v2 or later image format have a content-addressable identifier
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||
called a digest. As long as the input used to generate the image is unchanged,
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||
the digest value is predictable and referenceable.
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||
|
||
## PID settings (--pid)
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||
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||
--pid="" : Set the PID (Process) Namespace mode for the container,
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||
'host': use the host's PID namespace inside the container
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||
|
||
By default, all containers have the PID namespace enabled.
|
||
|
||
PID namespace provides separation of processes. The PID Namespace removes the
|
||
view of the system processes, and allows process ids to be reused including
|
||
pid 1.
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||
|
||
In certain cases you want your container to share the host's process namespace,
|
||
basically allowing processes within the container to see all of the processes
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||
on the system. For example, you could build a container with debugging tools
|
||
like `strace` or `gdb`, but want to use these tools when debugging processes
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||
within the container.
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||
|
||
$ docker run --pid=host rhel7 strace -p 1234
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||
|
||
This command would allow you to use `strace` inside the container on pid 1234 on
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||
the host.
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||
|
||
## UTS settings (--uts)
|
||
|
||
--uts="" : Set the UTS namespace mode for the container,
|
||
'host': use the host's UTS namespace inside the container
|
||
|
||
The UTS namespace is for setting the hostname and the domain that is visible
|
||
to running processes in that namespace. By default, all containers, including
|
||
those with `--net=host`, have their own UTS namespace. The `host` setting will
|
||
result in the container using the same UTS namespace as the host.
|
||
|
||
You may wish to share the UTS namespace with the host if you would like the
|
||
hostname of the container to change as the hostname of the host changes. A
|
||
more advanced use case would be changing the host's hostname from a container.
|
||
|
||
> **Note**: `--uts="host"` gives the container full access to change the
|
||
> hostname of the host and is therefore considered insecure.
|
||
|
||
## IPC settings (--ipc)
|
||
|
||
--ipc="" : Set the IPC mode for the container,
|
||
'container:<name|id>': reuses another container's IPC namespace
|
||
'host': use the host's IPC namespace inside the container
|
||
|
||
By default, all containers have the IPC namespace enabled.
|
||
|
||
IPC (POSIX/SysV IPC) namespace provides separation of named shared memory
|
||
segments, semaphores and message queues.
|
||
|
||
Shared memory segments are used to accelerate inter-process communication at
|
||
memory speed, rather than through pipes or through the network stack. Shared
|
||
memory is commonly used by databases and custom-built (typically C/OpenMPI,
|
||
C++/using boost libraries) high performance applications for scientific
|
||
computing and financial services industries. If these types of applications
|
||
are broken into multiple containers, you might need to share the IPC mechanisms
|
||
of the containers.
|
||
|
||
## Network settings
|
||
|
||
--dns=[] : Set custom dns servers for the container
|
||
--net="bridge" : Connects a container to a network
|
||
'bridge': creates a new network stack for the container on the docker bridge
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||
'none': no networking for this container
|
||
'container:<name|id>': reuses another container network stack
|
||
'host': use the host network stack inside the container
|
||
'NETWORK': connects the container to user-created network using `docker network create` command
|
||
--add-host="" : Add a line to /etc/hosts (host:IP)
|
||
--mac-address="" : Sets the container's Ethernet device's MAC address
|
||
|
||
By default, all containers have networking enabled and they can make any
|
||
outgoing connections. The operator can completely disable networking
|
||
with `docker run --net none` which disables all incoming and outgoing
|
||
networking. In cases like this, you would perform I/O through files or
|
||
`STDIN` and `STDOUT` only.
|
||
|
||
Publishing ports and linking to other containers only works with the the default (bridge). The linking feature is a legacy feature. You should always prefer using Docker network drivers over linking.
|
||
|
||
Your container will use the same DNS servers as the host by default, but
|
||
you can override this with `--dns`.
|
||
|
||
By default, the MAC address is generated using the IP address allocated to the
|
||
container. You can set the container's MAC address explicitly by providing a
|
||
MAC address via the `--mac-address` parameter (format:`12:34:56:78:9a:bc`).
|
||
|
||
Supported networks :
|
||
|
||
<table>
|
||
<thead>
|
||
<tr>
|
||
<th class="no-wrap">Network</th>
|
||
<th>Description</th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr>
|
||
<td class="no-wrap"><strong>none</strong></td>
|
||
<td>
|
||
No networking in the container.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td class="no-wrap"><strong>bridge</strong> (default)</td>
|
||
<td>
|
||
Connect the container to the bridge via veth interfaces.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td class="no-wrap"><strong>host</strong></td>
|
||
<td>
|
||
Use the host's network stack inside the container.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td class="no-wrap"><strong>container</strong>:<name|id></td>
|
||
<td>
|
||
Use the network stack of another container, specified via
|
||
its *name* or *id*.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td class="no-wrap"><strong>NETWORK</strong></td>
|
||
<td>
|
||
Connects the container to a user created network (using `docker network create` command)
|
||
</td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
|
||
#### Network: none
|
||
|
||
With the network is `none` a container will not have
|
||
access to any external routes. The container will still have a
|
||
`loopback` interface enabled in the container but it does not have any
|
||
routes to external traffic.
|
||
|
||
#### Network: bridge
|
||
|
||
With the network set to `bridge` a container will use docker's
|
||
default networking setup. A bridge is setup on the host, commonly named
|
||
`docker0`, and a pair of `veth` interfaces will be created for the
|
||
container. One side of the `veth` pair will remain on the host attached
|
||
to the bridge while the other side of the pair will be placed inside the
|
||
container's namespaces in addition to the `loopback` interface. An IP
|
||
address will be allocated for containers on the bridge's network and
|
||
traffic will be routed though this bridge to the container.
|
||
|
||
Containers can communicate via their IP addresses by default. To communicate by
|
||
name, they must be linked.
|
||
|
||
#### Network: host
|
||
|
||
With the network set to `host` a container will share the host's
|
||
network stack and all interfaces from the host will be available to the
|
||
container. The container's hostname will match the hostname on the host
|
||
system. Note that `--add-host` `--hostname` `--dns` `--dns-search`
|
||
`--dns-opt` and `--mac-address` are invalid in `host` netmode.
|
||
|
||
Compared to the default `bridge` mode, the `host` mode gives *significantly*
|
||
better networking performance since it uses the host's native networking stack
|
||
whereas the bridge has to go through one level of virtualization through the
|
||
docker daemon. It is recommended to run containers in this mode when their
|
||
networking performance is critical, for example, a production Load Balancer
|
||
or a High Performance Web Server.
|
||
|
||
> **Note**: `--net="host"` gives the container full access to local system
|
||
> services such as D-bus and is therefore considered insecure.
|
||
|
||
#### Network: container
|
||
|
||
With the network set to `container` a container will share the
|
||
network stack of another container. The other container's name must be
|
||
provided in the format of `--net container:<name|id>`. Note that `--add-host`
|
||
`--hostname` `--dns` `--dns-search` `--dns-opt` and `--mac-address` are
|
||
invalid in `container` netmode, and `--publish` `--publish-all` `--expose` are
|
||
also invalid in `container` netmode.
|
||
|
||
Example running a Redis container with Redis binding to `localhost` then
|
||
running the `redis-cli` command and connecting to the Redis server over the
|
||
`localhost` interface.
|
||
|
||
$ docker run -d --name redis example/redis --bind 127.0.0.1
|
||
$ # use the redis container's network stack to access localhost
|
||
$ docker run --rm -it --net container:redis example/redis-cli -h 127.0.0.1
|
||
|
||
#### User-defined network
|
||
|
||
You can create a network using a Docker network driver or an external network
|
||
driver plugin. You can connect multiple containers to the same network. Once
|
||
connected to a user-defined network, 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.
|
||
|
||
The following example creates a network using the built-in `bridge` network
|
||
driver and running a container in the created network
|
||
|
||
```
|
||
$ docker network create -d overlay my-net
|
||
$ docker run --net=my-net -itd --name=container3 busybox
|
||
```
|
||
|
||
### Managing /etc/hosts
|
||
|
||
Your container will have lines in `/etc/hosts` which define the hostname of the
|
||
container itself as well as `localhost` and a few other common things. The
|
||
`--add-host` flag can be used to add additional lines to `/etc/hosts`.
|
||
|
||
$ docker run -it --add-host db-static:86.75.30.9 ubuntu cat /etc/hosts
|
||
172.17.0.22 09d03f76bf2c
|
||
fe00::0 ip6-localnet
|
||
ff00::0 ip6-mcastprefix
|
||
ff02::1 ip6-allnodes
|
||
ff02::2 ip6-allrouters
|
||
127.0.0.1 localhost
|
||
::1 localhost ip6-localhost ip6-loopback
|
||
86.75.30.9 db-static
|
||
|
||
If a container is connected to the default bridge network and `linked`
|
||
with other containers, then the container's `/etc/hosts` file is updated
|
||
with the linked container's name.
|
||
|
||
If the container is connected to user-defined network, the container's
|
||
`/etc/hosts` file is updated with names of all other containers in that
|
||
user-defined network.
|
||
|
||
> **Note** Since Docker may live update the container’s `/etc/hosts` file, there
|
||
may be situations when processes inside the container can end up reading an
|
||
empty or incomplete `/etc/hosts` file. In most cases, retrying the read again
|
||
should fix the problem.
|
||
|
||
## Restart policies (--restart)
|
||
|
||
Using the `--restart` flag on Docker run you can specify a restart policy for
|
||
how a container should or should not be restarted on exit.
|
||
|
||
When a restart policy is active on a container, it will be shown as either `Up`
|
||
or `Restarting` in [`docker ps`](commandline/ps.md). It can also be
|
||
useful to use [`docker events`](commandline/events.md) to see the
|
||
restart policy in effect.
|
||
|
||
Docker supports the following restart policies:
|
||
|
||
<table>
|
||
<thead>
|
||
<tr>
|
||
<th>Policy</th>
|
||
<th>Result</th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr>
|
||
<td><strong>no</strong></td>
|
||
<td>
|
||
Do not automatically restart the container when it exits. This is the
|
||
default.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td>
|
||
<span style="white-space: nowrap">
|
||
<strong>on-failure</strong>[:max-retries]
|
||
</span>
|
||
</td>
|
||
<td>
|
||
Restart only if the container exits with a non-zero exit status.
|
||
Optionally, limit the number of restart retries the Docker
|
||
daemon attempts.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td><strong>always</strong></td>
|
||
<td>
|
||
Always restart the container regardless of the exit status.
|
||
When you specify always, the Docker daemon will try to restart
|
||
the container indefinitely. The container will also always start
|
||
on daemon startup, regardless of the current state of the container.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td><strong>unless-stopped</strong></td>
|
||
<td>
|
||
Always restart the container regardless of the exit status, but
|
||
do not start it on daemon startup if the container has been put
|
||
to a stopped state before.
|
||
</td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
|
||
An ever increasing delay (double the previous delay, starting at 100
|
||
milliseconds) is added before each restart to prevent flooding the server.
|
||
This means the daemon will wait for 100 ms, then 200 ms, 400, 800, 1600,
|
||
and so on until either the `on-failure` limit is hit, or when you `docker stop`
|
||
or `docker rm -f` the container.
|
||
|
||
If a container is successfully restarted (the container is started and runs
|
||
for at least 10 seconds), the delay is reset to its default value of 100 ms.
|
||
|
||
You can specify the maximum amount of times Docker will try to restart the
|
||
container when using the **on-failure** policy. The default is that Docker
|
||
will try forever to restart the container. The number of (attempted) restarts
|
||
for a container can be obtained via [`docker inspect`](commandline/inspect.md). For example, to get the number of restarts
|
||
for container "my-container";
|
||
|
||
$ docker inspect -f "{{ .RestartCount }}" my-container
|
||
# 2
|
||
|
||
Or, to get the last time the container was (re)started;
|
||
|
||
$ docker inspect -f "{{ .State.StartedAt }}" my-container
|
||
# 2015-03-04T23:47:07.691840179Z
|
||
|
||
You cannot set any restart policy in combination with
|
||
["clean up (--rm)"](#clean-up-rm). Setting both `--restart` and `--rm`
|
||
results in an error.
|
||
|
||
### Examples
|
||
|
||
$ 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.
|
||
|
||
$ docker run --restart=on-failure:10 redis
|
||
|
||
This will run the `redis` container with a restart policy of **on-failure**
|
||
and a maximum restart count of 10. If the `redis` container exits with a
|
||
non-zero exit status more than 10 times in a row Docker will abort trying to
|
||
restart the container. Providing a maximum restart limit is only valid for the
|
||
**on-failure** policy.
|
||
|
||
## Exit Status
|
||
|
||
The exit code from `docker run` gives information about why the container
|
||
failed to run or why it exited. When `docker run` exits with a non-zero code,
|
||
the exit codes follow the `chroot` standard, see below:
|
||
|
||
**_125_** if the error is with Docker daemon **_itself_**
|
||
|
||
$ docker run --foo busybox; echo $?
|
||
# flag provided but not defined: --foo
|
||
See 'docker run --help'.
|
||
125
|
||
|
||
**_126_** if the **_contained command_** cannot be invoked
|
||
|
||
$ docker run busybox /etc; echo $?
|
||
# exec: "/etc": permission denied
|
||
docker: Error response from daemon: Contained command could not be invoked
|
||
126
|
||
|
||
**_127_** if the **_contained command_** cannot be found
|
||
|
||
$ docker run busybox foo; echo $?
|
||
# exec: "foo": executable file not found in $PATH
|
||
docker: Error response from daemon: Contained command not found or does not exist
|
||
127
|
||
|
||
**_Exit code_** of **_contained command_** otherwise
|
||
|
||
$ docker run busybox /bin/sh -c 'exit 3'
|
||
# 3
|
||
|
||
## Clean up (--rm)
|
||
|
||
By default a container's file system persists even after the container
|
||
exits. This makes debugging a lot easier (since you can inspect the
|
||
final state) and you retain all your data by default. But if you are
|
||
running short-term **foreground** processes, these container file
|
||
systems can really pile up. If instead you'd like Docker to
|
||
**automatically clean up the container and remove the file system when
|
||
the container exits**, you can add the `--rm` flag:
|
||
|
||
--rm=false: Automatically remove the container when it exits (incompatible with -d)
|
||
|
||
> **Note**: When you set the `--rm` flag, Docker also removes the volumes
|
||
associated with the container when the container is removed. This is similar
|
||
to running `docker rm -v my-container`.
|
||
|
||
## Security configuration
|
||
--security-opt="label:user:USER" : Set the label user for the container
|
||
--security-opt="label:role:ROLE" : Set the label role for the container
|
||
--security-opt="label:type:TYPE" : Set the label type for the container
|
||
--security-opt="label:level:LEVEL" : Set the label level for the container
|
||
--security-opt="label:disable" : Turn off label confinement for the container
|
||
--security-opt="apparmor:PROFILE" : Set the apparmor profile to be applied
|
||
to the container
|
||
|
||
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.
|
||
|
||
## Specifying custom cgroups
|
||
|
||
Using the `--cgroup-parent` flag, you can pass a specific cgroup to run a
|
||
container in. This allows you to create and manage cgroups on their own. You can
|
||
define custom resources for those cgroups and put containers under a common
|
||
parent group.
|
||
|
||
## Runtime constraints on resources
|
||
|
||
The operator can also adjust the performance parameters of the
|
||
container:
|
||
|
||
| Option | Description |
|
||
|----------------------------|---------------------------------------------------------------------------------------------|
|
||
| `-m`, `--memory="" ` | Memory limit (format: `<number>[<unit>]`, where unit = b, k, m or g) |
|
||
| `--memory-swap=""` | Total memory limit (memory + swap, format: `<number>[<unit>]`, where unit = b, k, m or g) |
|
||
| `--memory-reservation=""` | Memory soft limit (format: `<number>[<unit>]`, where unit = b, k, m or g) |
|
||
| `--kernel-memory=""` | Kernel memory limit (format: `<number>[<unit>]`, where unit = b, k, m or g) |
|
||
| `-c`, `--cpu-shares=0` | CPU shares (relative weight) |
|
||
| `--cpu-period=0` | Limit the CPU CFS (Completely Fair Scheduler) period |
|
||
| `--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). Only effective on NUMA systems. |
|
||
| `--cpu-quota=0` | Limit the CPU CFS (Completely Fair Scheduler) quota |
|
||
| `--blkio-weight=0` | Block IO weight (relative weight) accepts a weight value between 10 and 1000. |
|
||
| `--blkio-weight-device=""` | Block IO weight (relative device weight, format: `DEVICE_NAME:WEIGHT`) |
|
||
| `--oom-kill-disable=false` | Whether to disable OOM Killer for the container or not. |
|
||
| `--memory-swappiness="" ` | Tune a container's memory swappiness behavior. Accepts an integer between 0 and 100. |
|
||
|
||
### User memory constraints
|
||
|
||
We have four ways to set user memory usage:
|
||
|
||
<table>
|
||
<thead>
|
||
<tr>
|
||
<th>Option</th>
|
||
<th>Result</th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr>
|
||
<td class="no-wrap">
|
||
<strong>memory=inf, memory-swap=inf</strong> (default)
|
||
</td>
|
||
<td>
|
||
There is no memory limit for the container. The container can use
|
||
as much memory as needed.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td class="no-wrap"><strong>memory=L<inf, memory-swap=inf</strong></td>
|
||
<td>
|
||
(specify memory and set memory-swap as <code>-1</code>) The container is
|
||
not allowed to use more than L bytes of memory, but can use as much swap
|
||
as is needed (if the host supports swap memory).
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td class="no-wrap"><strong>memory=L<inf, memory-swap=2*L</strong></td>
|
||
<td>
|
||
(specify memory without memory-swap) The container is not allowed to
|
||
use more than L bytes of memory, swap *plus* memory usage is double
|
||
of that.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td class="no-wrap">
|
||
<strong>memory=L<inf, memory-swap=S<inf, L<=S</strong>
|
||
</td>
|
||
<td>
|
||
(specify both memory and memory-swap) The container is not allowed to
|
||
use more than L bytes of memory, swap *plus* memory usage is limited
|
||
by S.
|
||
</td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
|
||
Examples:
|
||
|
||
$ docker run -ti ubuntu:14.04 /bin/bash
|
||
|
||
We set nothing about memory, this means the processes in the container can use
|
||
as much memory and swap memory as they need.
|
||
|
||
$ docker run -ti -m 300M --memory-swap -1 ubuntu:14.04 /bin/bash
|
||
|
||
We set memory limit and disabled swap memory limit, this means the processes in
|
||
the container can use 300M memory and as much swap memory as they need (if the
|
||
host supports swap memory).
|
||
|
||
$ docker run -ti -m 300M ubuntu:14.04 /bin/bash
|
||
|
||
We set memory limit only, this means the processes in the container can use
|
||
300M memory and 300M swap memory, by default, the total virtual memory size
|
||
(--memory-swap) will be set as double of memory, in this case, memory + swap
|
||
would be 2*300M, so processes can use 300M swap memory as well.
|
||
|
||
$ docker run -ti -m 300M --memory-swap 1G ubuntu:14.04 /bin/bash
|
||
|
||
We set both memory and swap memory, so the processes in the container can use
|
||
300M memory and 700M swap memory.
|
||
|
||
Memory reservation is a kind of memory soft limit that allows for greater
|
||
sharing of memory. Under normal circumstances, containers can use as much of
|
||
the memory as needed and are constrained only by the hard limits set with the
|
||
`-m`/`--memory` option. When memory reservation is set, Docker detects memory
|
||
contention or low memory and forces containers to restrict their consumption to
|
||
a reservation limit.
|
||
|
||
Always set the memory reservation value below the hard limit, otherwise the hard
|
||
limit takes precedence. A reservation of 0 is the same as setting no
|
||
reservation. By default (without reservation set), memory reservation is the
|
||
same as the hard memory limit.
|
||
|
||
Memory reservation is a soft-limit feature and does not guarantee the limit
|
||
won't be exceeded. Instead, the feature attempts to ensure that, when memory is
|
||
heavily contended for, memory is allocated based on the reservation hints/setup.
|
||
|
||
The following example limits the memory (`-m`) to 500M and sets the memory
|
||
reservation to 200M.
|
||
|
||
```bash
|
||
$ docker run -ti -m 500M --memory-reservation 200M ubuntu:14.04 /bin/bash
|
||
```
|
||
|
||
Under this configuration, when the container consumes memory more than 200M and
|
||
less than 500M, the next system memory reclaim attempts to shrink container
|
||
memory below 200M.
|
||
|
||
The following example set memory reservation to 1G without a hard memory limit.
|
||
|
||
```bash
|
||
$ docker run -ti --memory-reservation 1G ubuntu:14.04 /bin/bash
|
||
```
|
||
|
||
The container can use as much memory as it needs. The memory reservation setting
|
||
ensures the container doesn't consume too much memory for long time, because
|
||
every memory reclaim shrinks the container's consumption to the reservation.
|
||
|
||
By default, kernel kills processes in a container if an out-of-memory (OOM)
|
||
error occurs. To change this behaviour, use the `--oom-kill-disable` option.
|
||
Only disable the OOM killer on containers where you have also set the
|
||
`-m/--memory` option. If the `-m` flag is not set, this can result in the host
|
||
running out of memory and require killing the host's system processes to free
|
||
memory.
|
||
|
||
The following example limits the memory to 100M and disables the OOM killer for
|
||
this container:
|
||
|
||
$ docker run -ti -m 100M --oom-kill-disable ubuntu:14.04 /bin/bash
|
||
|
||
The following example, illustrates a dangerous way to use the flag:
|
||
|
||
$ docker run -ti --oom-kill-disable ubuntu:14.04 /bin/bash
|
||
|
||
The container has unlimited memory which can cause the host to run out memory
|
||
and require killing system processes to free memory.
|
||
|
||
### Kernel memory constraints
|
||
|
||
Kernel memory is fundamentally different than user memory as kernel memory can't
|
||
be swapped out. The inability to swap makes it possible for the container to
|
||
block system services by consuming too much kernel memory. Kernel memory includes:
|
||
|
||
- stack pages
|
||
- slab pages
|
||
- sockets memory pressure
|
||
- tcp memory pressure
|
||
|
||
You can setup kernel memory limit to constrain these kinds of memory. For example,
|
||
every process consumes some stack pages. By limiting kernel memory, you can
|
||
prevent new processes from being created when the kernel memory usage is too high.
|
||
|
||
Kernel memory is never completely independent of user memory. Instead, you limit
|
||
kernel memory in the context of the user memory limit. Assume "U" is the user memory
|
||
limit and "K" the kernel limit. There are three possible ways to set limits:
|
||
|
||
<table>
|
||
<thead>
|
||
<tr>
|
||
<th>Option</th>
|
||
<th>Result</th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr>
|
||
<td class="no-wrap"><strong>U != 0, K = inf</strong> (default)</td>
|
||
<td>
|
||
This is the standard memory limitation mechanism already present before using
|
||
kernel memory. Kernel memory is completely ignored.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td class="no-wrap"><strong>U != 0, K < U</strong></td>
|
||
<td>
|
||
Kernel memory is a subset of the user memory. This setup is useful in
|
||
deployments where the total amount of memory per-cgroup is overcommitted.
|
||
Overcommitting kernel memory limits is definitely not recommended, since the
|
||
box can still run out of non-reclaimable memory.
|
||
In this case, the you can configure K so that the sum of all groups is
|
||
never greater than the total memory. Then, freely set U at the expense of
|
||
the system's service quality.
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td class="no-wrap"><strong>U != 0, K > U</strong></td>
|
||
<td>
|
||
Since kernel memory charges are also fed to the user counter and reclamation
|
||
is triggered for the container for both kinds of memory. This configuration
|
||
gives the admin a unified view of memory. It is also useful for people
|
||
who just want to track kernel memory usage.
|
||
</td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
|
||
Examples:
|
||
|
||
$ docker run -ti -m 500M --kernel-memory 50M ubuntu:14.04 /bin/bash
|
||
|
||
We set memory and kernel memory, so the processes in the container can use
|
||
500M memory in total, in this 500M memory, it can be 50M kernel memory tops.
|
||
|
||
$ docker run -ti --kernel-memory 50M ubuntu:14.04 /bin/bash
|
||
|
||
We set kernel memory without **-m**, so the processes in the container can
|
||
use as much memory as they want, but they can only use 50M kernel memory.
|
||
|
||
### Swappiness constraint
|
||
|
||
By default, a container's kernel can swap out a percentage of anonymous pages.
|
||
To set this percentage for a container, specify a `--memory-swappiness` value
|
||
between 0 and 100. A value of 0 turns off anonymous page swapping. A value of
|
||
100 sets all anonymous pages as swappable. By default, if you are not using
|
||
`--memory-swappiness`, memory swappiness value will be inherited from the parent.
|
||
|
||
For example, you can set:
|
||
|
||
$ docker run -ti --memory-swappiness=0 ubuntu:14.04 /bin/bash
|
||
|
||
Setting the `--memory-swappiness` option is helpful when you want to retain the
|
||
container's working set and to avoid swapping performance penalties.
|
||
|
||
### CPU share constraint
|
||
|
||
By default, all containers get the same proportion of CPU cycles. This proportion
|
||
can be modified by changing the container's CPU share weighting relative
|
||
to the weighting of all other running containers.
|
||
|
||
To modify the proportion from the default of 1024, use the `-c` or `--cpu-shares`
|
||
flag to set the weighting to 2 or higher. If 0 is set, the system will ignore the
|
||
value and use the default of 1024.
|
||
|
||
The proportion will only apply when CPU-intensive processes are running.
|
||
When tasks in one container are idle, other containers can use the
|
||
left-over CPU time. The actual amount of CPU time will vary depending on
|
||
the number of containers running on the system.
|
||
|
||
For example, consider three containers, one has a cpu-share of 1024 and
|
||
two others have a cpu-share setting of 512. When processes in all three
|
||
containers attempt to use 100% of CPU, the first container would receive
|
||
50% of the total CPU time. If you add a fourth container with a cpu-share
|
||
of 1024, the first container only gets 33% of the CPU. The remaining containers
|
||
receive 16.5%, 16.5% and 33% of the CPU.
|
||
|
||
On a multi-core system, the shares of CPU time are distributed over all CPU
|
||
cores. Even if a container is limited to less than 100% of CPU time, it can
|
||
use 100% of each individual CPU core.
|
||
|
||
For example, consider a system with more than three cores. If you start one
|
||
container `{C0}` with `-c=512` running one process, and another container
|
||
`{C1}` with `-c=1024` running two processes, this can result in the following
|
||
division of CPU shares:
|
||
|
||
PID container CPU CPU share
|
||
100 {C0} 0 100% of CPU0
|
||
101 {C1} 1 100% of CPU1
|
||
102 {C1} 2 100% of CPU2
|
||
|
||
### CPU period constraint
|
||
|
||
The default CPU CFS (Completely Fair Scheduler) period is 100ms. We can use
|
||
`--cpu-period` to set the period of CPUs to limit the container's CPU usage.
|
||
And usually `--cpu-period` should work with `--cpu-quota`.
|
||
|
||
Examples:
|
||
|
||
$ docker run -ti --cpu-period=50000 --cpu-quota=25000 ubuntu:14.04 /bin/bash
|
||
|
||
If there is 1 CPU, this means the container can get 50% CPU worth of run-time every 50ms.
|
||
|
||
For more information, see the [CFS documentation on bandwidth limiting](https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt).
|
||
|
||
### Cpuset constraint
|
||
|
||
We can set cpus in which to allow execution for containers.
|
||
|
||
Examples:
|
||
|
||
$ docker run -ti --cpuset-cpus="1,3" ubuntu:14.04 /bin/bash
|
||
|
||
This means processes in container can be executed on cpu 1 and cpu 3.
|
||
|
||
$ docker run -ti --cpuset-cpus="0-2" ubuntu:14.04 /bin/bash
|
||
|
||
This means processes in container can be executed on cpu 0, cpu 1 and cpu 2.
|
||
|
||
We can set mems in which to allow execution for containers. Only effective
|
||
on NUMA systems.
|
||
|
||
Examples:
|
||
|
||
$ docker run -ti --cpuset-mems="1,3" ubuntu:14.04 /bin/bash
|
||
|
||
This example restricts the processes in the container to only use memory from
|
||
memory nodes 1 and 3.
|
||
|
||
$ docker run -ti --cpuset-mems="0-2" ubuntu:14.04 /bin/bash
|
||
|
||
This example restricts the processes in the container to only use memory from
|
||
memory nodes 0, 1 and 2.
|
||
|
||
### CPU quota constraint
|
||
|
||
The `--cpu-quota` flag limits the container's CPU usage. The default 0 value
|
||
allows the container to take 100% of a CPU resource (1 CPU). The CFS (Completely Fair
|
||
Scheduler) handles resource allocation for executing processes and is default
|
||
Linux Scheduler used by the kernel. Set this value to 50000 to limit the container
|
||
to 50% of a CPU resource. For multiple CPUs, adjust the `--cpu-quota` as necessary.
|
||
For more information, see the [CFS documentation on bandwidth limiting](https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt).
|
||
|
||
### Block IO bandwidth (Blkio) constraint
|
||
|
||
By default, all containers get the same proportion of block IO bandwidth
|
||
(blkio). This proportion is 500. To modify this proportion, change the
|
||
container's blkio weight relative to the weighting of all other running
|
||
containers using the `--blkio-weight` flag.
|
||
|
||
> **Note:** The blkio weight setting is only available for direct IO. Buffered IO
|
||
> is not currently supported.
|
||
|
||
The `--blkio-weight` flag can set the weighting to a value between 10 to 1000.
|
||
For example, the commands below create two containers with different blkio
|
||
weight:
|
||
|
||
$ docker run -ti --name c1 --blkio-weight 300 ubuntu:14.04 /bin/bash
|
||
$ docker run -ti --name c2 --blkio-weight 600 ubuntu:14.04 /bin/bash
|
||
|
||
If you do block IO in the two containers at the same time, by, for example:
|
||
|
||
$ time dd if=/mnt/zerofile of=test.out bs=1M count=1024 oflag=direct
|
||
|
||
You'll find that the proportion of time is the same as the proportion of blkio
|
||
weights of the two containers.
|
||
|
||
The `--blkio-weight-device="DEVICE_NAME:WEIGHT"` flag sets a specific device weight.
|
||
The `DEVICE_NAME:WEIGHT` is a string containing a colon-separated device name and weight.
|
||
For example, to set `/dev/sda` device weight to `200`:
|
||
|
||
$ docker run -it \
|
||
--blkio-weight-device "/dev/sda:200" \
|
||
ubuntu
|
||
|
||
If you specify both the `--blkio-weight` and `--blkio-weight-device`, Docker
|
||
uses the `--blkio-weight` as the default weight and uses `--blkio-weight-device`
|
||
to override this default with a new value on a specific device.
|
||
The following example uses a default weight of `300` and overrides this default
|
||
on `/dev/sda` setting that weight to `200`:
|
||
|
||
$ docker run -it \
|
||
--blkio-weight 300 \
|
||
--blkio-weight-device "/dev/sda:200" \
|
||
ubuntu
|
||
|
||
## Additional groups
|
||
--group-add: Add Linux capabilities
|
||
|
||
By default, the docker container process runs with the supplementary groups looked
|
||
up for the specified user. If one wants to add more to that list of groups, then
|
||
one can use this flag:
|
||
|
||
$ docker run -ti --rm --group-add audio --group-add dbus --group-add 777 busybox id
|
||
uid=0(root) gid=0(root) groups=10(wheel),29(audio),81(dbus),777
|
||
|
||
## Runtime privilege and Linux capabilities
|
||
|
||
--cap-add: Add Linux capabilities
|
||
--cap-drop: Drop Linux capabilities
|
||
--privileged=false: Give extended privileges to this container
|
||
--device=[]: Allows you to run devices inside the container without the --privileged flag.
|
||
|
||
By default, Docker containers are "unprivileged" and cannot, for
|
||
example, run a Docker daemon inside a Docker container. This is because
|
||
by default a container is not allowed to access any devices, but a
|
||
"privileged" container is given access to all devices (see
|
||
the documentation on [cgroups devices](https://www.kernel.org/doc/Documentation/cgroups/devices.txt)).
|
||
|
||
When the operator executes `docker run --privileged`, Docker will enable
|
||
to access to all devices on the host as well as set some configuration
|
||
in AppArmor or SELinux to allow the container nearly all the same access to the
|
||
host as processes running outside containers on the host. Additional
|
||
information about running with `--privileged` is available on the
|
||
[Docker Blog](http://blog.docker.com/2013/09/docker-can-now-run-within-docker/).
|
||
|
||
If you want to limit access to a specific device or devices you can use
|
||
the `--device` flag. It allows you to specify one or more devices that
|
||
will be accessible within the container.
|
||
|
||
$ docker run --device=/dev/snd:/dev/snd ...
|
||
|
||
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:w --rm -it ubuntu fdisk /dev/xvdc
|
||
crash....
|
||
|
||
$ docker run --device=/dev/sda:/dev/xvdc:m --rm -it ubuntu fdisk /dev/xvdc
|
||
fdisk: unable to open /dev/xvdc: Operation not permitted
|
||
|
||
In addition to `--privileged`, the operator can have fine grain control over the
|
||
capabilities using `--cap-add` and `--cap-drop`. By default, Docker has a default
|
||
list of capabilities that are kept. The following table lists the Linux capability options which can be added or dropped.
|
||
|
||
| Capability Key | Capability Description |
|
||
| -------------- | ---------------------- |
|
||
| SETPCAP | Modify process capabilities. |
|
||
| SYS_MODULE| Load and unload kernel modules. |
|
||
| SYS_RAWIO | Perform I/O port operations (iopl(2) and ioperm(2)). |
|
||
| SYS_PACCT | Use acct(2), switch process accounting on or off. |
|
||
| SYS_ADMIN | Perform a range of system administration operations. |
|
||
| SYS_NICE | Raise process nice value (nice(2), setpriority(2)) and change the nice value for arbitrary processes. |
|
||
| SYS_RESOURCE | Override resource Limits. |
|
||
| SYS_TIME | Set system clock (settimeofday(2), stime(2), adjtimex(2)); set real-time (hardware) clock. |
|
||
| SYS_TTY_CONFIG | Use vhangup(2); employ various privileged ioctl(2) operations on virtual terminals. |
|
||
| MKNOD | Create special files using mknod(2). |
|
||
| AUDIT_WRITE | Write records to kernel auditing log. |
|
||
| AUDIT_CONTROL | Enable and disable kernel auditing; change auditing filter rules; retrieve auditing status and filtering rules. |
|
||
| MAC_OVERRIDE | Allow MAC configuration or state changes. Implemented for the Smack LSM. |
|
||
| MAC_ADMIN | Override Mandatory Access Control (MAC). Implemented for the Smack Linux Security Module (LSM). |
|
||
| NET_ADMIN | Perform various network-related operations. |
|
||
| SYSLOG | Perform privileged syslog(2) operations. |
|
||
| CHOWN | Make arbitrary changes to file UIDs and GIDs (see chown(2)). |
|
||
| NET_RAW | Use RAW and PACKET sockets. |
|
||
| DAC_OVERRIDE | Bypass file read, write, and execute permission checks. |
|
||
| FOWNER | Bypass permission checks on operations that normally require the file system UID of the process to match the UID of the file. |
|
||
| DAC_READ_SEARCH | Bypass file read permission checks and directory read and execute permission checks. |
|
||
| FSETID | Don't clear set-user-ID and set-group-ID permission bits when a file is modified. |
|
||
| KILL | Bypass permission checks for sending signals. |
|
||
| SETGID | Make arbitrary manipulations of process GIDs and supplementary GID list. |
|
||
| SETUID | Make arbitrary manipulations of process UIDs. |
|
||
| LINUX_IMMUTABLE | Set the FS_APPEND_FL and FS_IMMUTABLE_FL i-node flags. |
|
||
| NET_BIND_SERVICE | Bind a socket to internet domain privileged ports (port numbers less than 1024). |
|
||
| NET_BROADCAST | Make socket broadcasts, and listen to multicasts. |
|
||
| IPC_LOCK | Lock memory (mlock(2), mlockall(2), mmap(2), shmctl(2)). |
|
||
| IPC_OWNER | Bypass permission checks for operations on System V IPC objects. |
|
||
| SYS_CHROOT | Use chroot(2), change root directory. |
|
||
| SYS_PTRACE | Trace arbitrary processes using ptrace(2). |
|
||
| SYS_BOOT | Use reboot(2) and kexec_load(2), reboot and load a new kernel for later execution. |
|
||
| LEASE | Establish leases on arbitrary files (see fcntl(2)). |
|
||
| SETFCAP | Set file capabilities.|
|
||
| WAKE_ALARM | Trigger something that will wake up the system. |
|
||
| BLOCK_SUSPEND | Employ features that can block system suspend. |
|
||
|
||
Further reference information is available on the [capabilities(7) - Linux man page](http://linux.die.net/man/7/capabilities)
|
||
|
||
Both flags support the value `ALL`, so if the
|
||
operator wants to have all capabilities but `MKNOD` they could use:
|
||
|
||
$ docker run --cap-add=ALL --cap-drop=MKNOD ...
|
||
|
||
For interacting with the network stack, instead of using `--privileged` they
|
||
should use `--cap-add=NET_ADMIN` to modify the network interfaces.
|
||
|
||
$ docker run -t -i --rm ubuntu:14.04 ip link add dummy0 type dummy
|
||
RTNETLINK answers: Operation not permitted
|
||
$ docker run -t -i --rm --cap-add=NET_ADMIN ubuntu:14.04 ip link add dummy0 type dummy
|
||
|
||
To mount a FUSE based filesystem, you need to combine both `--cap-add` and
|
||
`--device`:
|
||
|
||
$ docker run --rm -it --cap-add SYS_ADMIN sshfs sshfs sven@10.10.10.20:/home/sven /mnt
|
||
fuse: failed to open /dev/fuse: Operation not permitted
|
||
$ docker run --rm -it --device /dev/fuse sshfs sshfs sven@10.10.10.20:/home/sven /mnt
|
||
fusermount: mount failed: Operation not permitted
|
||
$ docker run --rm -it --cap-add SYS_ADMIN --device /dev/fuse sshfs
|
||
# sshfs sven@10.10.10.20:/home/sven /mnt
|
||
The authenticity of host '10.10.10.20 (10.10.10.20)' can't be established.
|
||
ECDSA key fingerprint is 25:34:85:75:25:b0:17:46:05:19:04:93:b5:dd:5f:c6.
|
||
Are you sure you want to continue connecting (yes/no)? yes
|
||
sven@10.10.10.20's password:
|
||
root@30aa0cfaf1b5:/# ls -la /mnt/src/docker
|
||
total 1516
|
||
drwxrwxr-x 1 1000 1000 4096 Dec 4 06:08 .
|
||
drwxrwxr-x 1 1000 1000 4096 Dec 4 11:46 ..
|
||
-rw-rw-r-- 1 1000 1000 16 Oct 8 00:09 .dockerignore
|
||
-rwxrwxr-x 1 1000 1000 464 Oct 8 00:09 .drone.yml
|
||
drwxrwxr-x 1 1000 1000 4096 Dec 4 06:11 .git
|
||
-rw-rw-r-- 1 1000 1000 461 Dec 4 06:08 .gitignore
|
||
....
|
||
|
||
|
||
## Logging drivers (--log-driver)
|
||
|
||
The container can have a different logging driver than the Docker daemon. Use
|
||
the `--log-driver=VALUE` with the `docker run` command to configure the
|
||
container's logging driver. The following options are supported:
|
||
|
||
| `none` | Disables any logging for the container. `docker logs` won't be available with this driver. |
|
||
|-------------|-------------------------------------------------------------------------------------------------------------------------------|
|
||
| `json-file` | Default logging driver for Docker. Writes JSON messages to file. No logging options are supported for this driver. |
|
||
| `syslog` | Syslog logging driver for Docker. Writes log messages to syslog. |
|
||
| `journald` | Journald logging driver for Docker. Writes log messages to `journald`. |
|
||
| `gelf` | Graylog Extended Log Format (GELF) logging driver for Docker. Writes log messages to a GELF endpoint likeGraylog or Logstash. |
|
||
| `fluentd` | Fluentd logging driver for Docker. Writes log messages to `fluentd` (forward input). |
|
||
| `awslogs` | Amazon CloudWatch Logs logging driver for Docker. Writes log messages to Amazon CloudWatch Logs |
|
||
| `splunk` | Splunk logging driver for Docker. Writes log messages to `splunk` using Event Http Collector. |
|
||
|
||
The `docker logs` command is available only for the `json-file` and `journald`
|
||
logging drivers. For detailed information on working with logging drivers, see
|
||
[Configure a logging driver](logging/overview.md).
|
||
|
||
|
||
## Overriding Dockerfile image defaults
|
||
|
||
When a developer builds an image from a [*Dockerfile*](builder.md)
|
||
or when she commits it, the developer can set a number of default parameters
|
||
that take effect when the image starts up as a container.
|
||
|
||
Four of the Dockerfile commands cannot be overridden at runtime: `FROM`,
|
||
`MAINTAINER`, `RUN`, and `ADD`. Everything else has a corresponding override
|
||
in `docker run`. We'll go through what the developer might have set in each
|
||
Dockerfile instruction and how the operator can override that setting.
|
||
|
||
- [CMD (Default Command or Options)](#cmd-default-command-or-options)
|
||
- [ENTRYPOINT (Default Command to Execute at Runtime)](
|
||
#entrypoint-default-command-to-execute-at-runtime)
|
||
- [EXPOSE (Incoming Ports)](#expose-incoming-ports)
|
||
- [ENV (Environment Variables)](#env-environment-variables)
|
||
- [VOLUME (Shared Filesystems)](#volume-shared-filesystems)
|
||
- [USER](#user)
|
||
- [WORKDIR](#workdir)
|
||
|
||
### CMD (default command or options)
|
||
|
||
Recall the optional `COMMAND` in the Docker
|
||
commandline:
|
||
|
||
$ docker run [OPTIONS] IMAGE[:TAG|@DIGEST] [COMMAND] [ARG...]
|
||
|
||
This command is optional because the person who created the `IMAGE` may
|
||
have already provided a default `COMMAND` using the Dockerfile `CMD`
|
||
instruction. As the operator (the person running a container from the
|
||
image), you can override that `CMD` instruction just by specifying a new
|
||
`COMMAND`.
|
||
|
||
If the image also specifies an `ENTRYPOINT` then the `CMD` or `COMMAND`
|
||
get appended as arguments to the `ENTRYPOINT`.
|
||
|
||
### ENTRYPOINT (default command to execute at runtime)
|
||
|
||
--entrypoint="": Overwrite the default entrypoint set by the image
|
||
|
||
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 string to specify the new `ENTRYPOINT`. Here is an
|
||
example of how to run a shell in a container that has been set up to
|
||
automatically run something else (like `/usr/bin/redis-server`):
|
||
|
||
$ docker run -i -t --entrypoint /bin/bash example/redis
|
||
|
||
or two examples of how to pass more parameters to that ENTRYPOINT:
|
||
|
||
$ docker run -i -t --entrypoint /bin/bash example/redis -c ls -l
|
||
$ docker run -i -t --entrypoint /usr/bin/redis-cli example/redis --help
|
||
|
||
### EXPOSE (incoming ports)
|
||
|
||
The following `run` command options work with container networking:
|
||
|
||
--expose=[]: Expose a port or a range of ports inside the container.
|
||
These are additional to those exposed by the `EXPOSE` instruction
|
||
-P=false : Publish all exposed ports to the host interfaces
|
||
-p=[] : Publish a container᾿s port or a 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, for example:
|
||
-p 1234-1236:1234-1236/tcp
|
||
|
||
When specifying a range for hostPort only, the
|
||
containerPort must not be a range. In this case the
|
||
container port is published somewhere within the
|
||
specified hostPort range. (e.g., `-p 1234-1236:1234/tcp`)
|
||
|
||
(use 'docker port' to see the actual mapping)
|
||
|
||
--link="" : Add link to another container (<name or id>:alias or <name or id>)
|
||
|
||
With the exception of the `EXPOSE` directive, an image developer hasn't
|
||
got much control over networking. The `EXPOSE` instruction defines the
|
||
initial incoming ports that provide services. These ports are available
|
||
to processes inside the container. An operator can use the `--expose`
|
||
option to add to the exposed ports.
|
||
|
||
To expose a container's internal port, an operator can start the
|
||
container with the `-P` or `-p` flag. The exposed port is accessible on
|
||
the host and the ports are available to any client that can reach the
|
||
host.
|
||
|
||
The `-P` option publishes all the ports to the host interfaces. Docker
|
||
binds each exposed port to a random port on the host. The range of
|
||
ports are within an *ephemeral port range* defined by
|
||
`/proc/sys/net/ipv4/ip_local_port_range`. Use the `-p` flag to
|
||
explicitly map a single port or range of ports.
|
||
|
||
The port number inside the container (where the service listens) does
|
||
not need to match the port number exposed on the outside of the
|
||
container (where clients connect). For example, inside the container an
|
||
HTTP service is listening on port 80 (and so the image developer
|
||
specifies `EXPOSE 80` in the Dockerfile). At runtime, the port might be
|
||
bound to 42800 on the host. To find the mapping between the host ports
|
||
and the exposed ports, use `docker port`.
|
||
|
||
If the operator uses `--link` when starting a new client container, then the
|
||
client container can access the exposed port via a private networking interface.
|
||
Linking is a legacy feature that is only supported on the default bridge
|
||
network. You should prefer the Docker networks feature instead. For more
|
||
information on this feature, see the [*Docker network
|
||
overview*""](../userguide/networking/index.md)).
|
||
|
||
### ENV (environment variables)
|
||
|
||
When a new container is created, Docker will set the following environment
|
||
variables automatically:
|
||
|
||
<table>
|
||
<tr>
|
||
<th>Variable</th>
|
||
<th>Value</th>
|
||
</tr>
|
||
<tr>
|
||
<td><code>HOME</code></td>
|
||
<td>
|
||
Set based on the value of <code>USER</code>
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td><code>HOSTNAME</code></td>
|
||
<td>
|
||
The hostname associated with the container
|
||
</td>
|
||
</tr>
|
||
<tr>
|
||
<td><code>PATH</code></td>
|
||
<td>
|
||
Includes popular directories, such as :<br>
|
||
<code>/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin</code>
|
||
</td>
|
||
<tr>
|
||
<td><code>TERM</code></td>
|
||
<td><code>xterm</code> if the container is allocated a pseudo-TTY</td>
|
||
</tr>
|
||
</table>
|
||
|
||
Additionally, the operator can **set any environment variable** in the
|
||
container by using one or more `-e` flags, even overriding those mentioned
|
||
above, or already defined by the developer with a Dockerfile `ENV`:
|
||
|
||
$ docker run -e "deep=purple" --rm ubuntu /bin/bash -c export
|
||
declare -x HOME="/"
|
||
declare -x HOSTNAME="85bc26a0e200"
|
||
declare -x OLDPWD
|
||
declare -x PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
|
||
declare -x PWD="/"
|
||
declare -x SHLVL="1"
|
||
declare -x deep="purple"
|
||
|
||
Similarly the operator can set the **hostname** with `-h`.
|
||
|
||
### VOLUME (shared filesystems)
|
||
|
||
-v=[]: Create a bind mount with: [host-dir:]container-dir[:<options>], where
|
||
options are comma delimited and selected from [rw|ro] and [z|Z].
|
||
If 'host-dir' is missing, then docker creates a new volume.
|
||
If neither 'rw' or 'ro' is specified then the volume is mounted
|
||
in read-write mode.
|
||
--volumes-from="": Mount all volumes from the given container(s)
|
||
|
||
> **Note**:
|
||
> The auto-creation of the host path has been [*deprecated*](../misc/deprecated.md#auto-creating-missing-host-paths-for-bind-mounts).
|
||
|
||
The volumes commands are complex enough to have their own documentation
|
||
in section [*Managing data in
|
||
containers*](../userguide/dockervolumes.md). A developer can define
|
||
one or more `VOLUME`'s associated with an image, but only the operator
|
||
can give access from one container to another (or from a container to a
|
||
volume mounted on the host).
|
||
|
||
The `container-dir` must always be an absolute path such as `/src/docs`.
|
||
The `host-dir` can either be an absolute path or a `name` value. If you
|
||
supply an absolute path for the `host-dir`, Docker bind-mounts to the path
|
||
you specify. If you supply a `name`, Docker creates a named volume by that `name`.
|
||
|
||
A `name` value must start with start with an alphanumeric character,
|
||
followed by `a-z0-9`, `_` (underscore), `.` (period) or `-` (hyphen).
|
||
An absolute path starts with a `/` (forward slash).
|
||
|
||
For example, you can specify either `/foo` or `foo` for a `host-dir` value.
|
||
If you supply the `/foo` value, Docker creates a bind-mount. If you supply
|
||
the `foo` specification, Docker creates a named volume.
|
||
|
||
### USER
|
||
|
||
`root` (id = 0) is the default user within a container. The image developer can
|
||
create additional users. Those users are accessible by name. When passing a numeric
|
||
ID, the user does not have to exist in the container.
|
||
|
||
The developer can set a default user to run the first process with the
|
||
Dockerfile `USER` instruction. When starting a container, the operator can override
|
||
the `USER` instruction by passing the `-u` option.
|
||
|
||
-u="": Username or UID
|
||
|
||
> **Note:** if you pass a numeric uid, it must be in the range of 0-2147483647.
|
||
|
||
### WORKDIR
|
||
|
||
The default working directory for running binaries within a container is the
|
||
root directory (`/`), but the developer can set a different default with the
|
||
Dockerfile `WORKDIR` command. The operator can override this with:
|
||
|
||
-w="": Working directory inside the container
|