<!--[metadata]>
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title = "update"
description = "The update command description and usage"
keywords = ["resources, update, dynamically"]
[menu.main]
parent = "smn_cli"
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<![end-metadata]-->

## update

```markdown
Usage:  docker update [OPTIONS] CONTAINER [CONTAINER...]

Update configuration of one or more containers

Options:
      --blkio-weight value          Block IO (relative weight), between 10 and 1000
      --cpu-period int              Limit CPU CFS (Completely Fair Scheduler) period
      --cpu-quota int               Limit CPU CFS (Completely Fair Scheduler) quota
  -c, --cpu-shares int              CPU shares (relative weight)
      --cpuset-cpus string          CPUs in which to allow execution (0-3, 0,1)
      --cpuset-mems string          MEMs in which to allow execution (0-3, 0,1)
      --help                        Print usage
      --kernel-memory string        Kernel memory limit
  -m, --memory string               Memory limit
      --memory-reservation string   Memory soft limit
      --memory-swap string          Swap limit equal to memory plus swap: '-1' to enable unlimited swap
      --restart string              Restart policy to apply when a container exits
```

The `docker update` command dynamically updates container configuration.
You can use this command to prevent containers from consuming too many 
resources from their Docker host.  With a single command, you can place 
limits on a single container or on many. To specify more than one container,
provide space-separated list of container names or IDs.

With the exception of the `--kernel-memory` option, you can specify these
options on a running or a stopped container. On kernel version older than
4.6, you can only update `--kernel-memory` on a stopped container or on
a running container with kernel memory initialized.

## EXAMPLES

The following sections illustrate ways to use this command.

### Update a container's cpu-shares

To limit a container's cpu-shares to 512, first identify the container
name or ID. You can use `docker ps` to find these values. You can also
use the ID returned from the `docker run` command.  Then, do the following:

```bash
$ docker update --cpu-shares 512 abebf7571666
```

### Update a container with cpu-shares and memory

To update multiple resource configurations for multiple containers:

```bash
$ docker update --cpu-shares 512 -m 300M abebf7571666 hopeful_morse
```

### Update a container's kernel memory constraints

You can update a container's kernel memory limit using the `--kernel-memory`
option. On kernel version older than 4.6, this option can be updated on a
running container only if the container was started with `--kernel-memory`.
If the container was started *without* `--kernel-memory` you need to stop
the container before updating kernel memory.

For example, if you started a container with this command:

```bash
$ docker run -dit --name test --kernel-memory 50M ubuntu bash
```

You can update kernel memory while the container is running:

```bash
$ docker update --kernel-memory 80M test
```

If you started a container *without* kernel memory initialized:

```bash
$ docker run -dit --name test2 --memory 300M ubuntu bash
```

Update kernel memory of running container `test2` will fail. You need to stop
the container before updating the `--kernel-memory` setting. The next time you
start it, the container uses the new value.

Kernel version newer than (include) 4.6 does not have this limitation, you
can use `--kernel-memory` the same way as other options.

### Update a container's restart policy

You can change a container's restart policy on a running container. The new
restart policy takes effect instantly after you run `docker update` on a
container.

To update restart policy for one or more containers:

```bash
$ docker update --restart=on-failure:3 abebf7571666 hopeful_morse
```
