DockerCLI/docs/reference/commandline/update.md

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## update
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Update configuration of one or more containers
### Aliases
`docker container update`, `docker update`
### Options
| Name | Type | Default | Description |
|:---------------------------------------------------|:----------|:--------|:-----------------------------------------------------------------------------|
| `--blkio-weight` | `uint16` | `0` | Block IO (relative weight), between 10 and 1000, or 0 to disable (default 0) |
| `--cpu-period` | `int64` | `0` | Limit CPU CFS (Completely Fair Scheduler) period |
| `--cpu-quota` | `int64` | `0` | Limit CPU CFS (Completely Fair Scheduler) quota |
| `--cpu-rt-period` | `int64` | `0` | Limit the CPU real-time period in microseconds |
| `--cpu-rt-runtime` | `int64` | `0` | Limit the CPU real-time runtime in microseconds |
| [`-c`](#cpu-shares), [`--cpu-shares`](#cpu-shares) | `int64` | `0` | CPU shares (relative weight) |
| `--cpus` | `decimal` | | Number of CPUs |
| `--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) |
| [`-m`](#memory), [`--memory`](#memory) | `bytes` | `0` | Memory limit |
| `--memory-reservation` | `bytes` | `0` | Memory soft limit |
| `--memory-swap` | `bytes` | `0` | Swap limit equal to memory plus swap: -1 to enable unlimited swap |
| `--pids-limit` | `int64` | `0` | Tune container pids limit (set -1 for unlimited) |
| [`--restart`](#restart) | `string` | | Restart policy to apply when a container exits |
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## Description
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.
> **Warning**
>
> The `docker update` and `docker container update` commands are not supported
> for Windows containers.
{ .warning }
## Examples
The following sections illustrate ways to use this command.
### <a name="cpu-shares"></a> Update a container's cpu-shares (--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:
```console
$ docker update --cpu-shares 512 abebf7571666
```
### <a name="memory"></a> Update a container with cpu-shares and memory (-m, --memory)
To update multiple resource configurations for multiple containers:
```console
$ docker update --cpu-shares 512 -m 300M abebf7571666 hopeful_morse
```
### <a name="kernel-memory"></a> Update a container's kernel memory constraints (--kernel-memory)
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.
> **Note**
>
> The `--kernel-memory` option has been deprecated since Docker 20.10.
For example, if you started a container with this command:
```console
$ docker run -dit --name test --kernel-memory 50M ubuntu bash
```
You can update kernel memory while the container is running:
```console
$ docker update --kernel-memory 80M test
```
If you started a container without kernel memory initialized:
```console
$ 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.
### <a name="restart"></a> Update a container's restart policy (--restart)
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:
```console
$ docker update --restart=on-failure:3 abebf7571666 hopeful_morse
```
Note that if the container is started with `--rm` flag, you cannot update the restart
policy for it. The `AutoRemove` and `RestartPolicy` are mutually exclusive for the
container.