<p>I use the command <code>docker container update --cpus 1 target_container</code> to update the setting. But in most cases it not working and response "you must provide one or more flags when using this command", but somethings it working</p>

<p>Any one know the reason?</p>

<p>Some log is like,</p>

<pre><code>$ docker container update --cpus 0.5 target_container
you must provide one or more flags when using this command
$ docker container update --cpus 0.5 target_container
you must provide one or more flags when using this command
$ docker container update --cpus 0.5 target_container
target_container
</code></pre>

<p>the docker version is </p>

<pre><code>Client:
 Version:           18.09.7
 API version:       1.39
 Go version:        go1.10.4
 Git commit:        2d0083d
 Built:             Fri Aug 16 14:19:38 2019
 OS/Arch:           linux/amd64
 Experimental:      false

Server:
 Engine:
  Version:          18.09.7
  API version:      1.39 (minimum version 1.12)
  Go version:       go1.10.4
  Git commit:       2d0083d
  Built:            Thu Aug 15 15:12:41 2019
  OS/Arch:          linux/amd64
  Experimental:     false
</code></pre>

<p>The <a href="https://docs.docker.com/engine/reference/commandline/update/" rel="nofollow noreferrer">docker update</a> man page includes:</p>

<pre><code>--cpus      API 1.29+
</code></pre>

<p>A <code>docker version</code> can show you if your API is equal or above <a href="https://docs.docker.com/engine/api/v1.29/" rel="nofollow noreferrer">the API 29</a>, which was with  Docker 17.05.</p>

<p>For testing, try <code>--cpus=1</code> or <code>--cpus=0.5</code>, considering the argument is supposed to be "number of CPUs"</p>

<p>As usual with commands including an hyphen: <a href="https://stackoverflow.com/a/170148/6309">don't copy-paste it</a>, copy it manually.</p>
