<p>It turns out there was a leftover file from a previous version of docker at <code>/etc/systemd/system/docker.service.d/service-overrides.conf</code> that was injecting environment variables into the docker.service ExecStart command.</p>
<pre><code># cat /etc/systemd/system/docker.service.d/service-overrides.conf
[Service]
EnvironmentFile=-/etc/sysconfig/docker
EnvironmentFile=-/etc/sysconfig/docker-storage
EnvironmentFile=-/etc/sysconfig/docker-network
ExecStart=
ExecStart=/usr/bin/docker daemon $OPTIONS \
      $DOCKER_STORAGE_OPTIONS \
      $DOCKER_NETWORK_OPTIONS \
      $BLOCK_REGISTRY \
      $INSECURE_REGISTRY
</code></pre>
<p>I removed this file and rebooted, then docker started successfully.</p>

CC BY-SA 4.0
2023-10-06T03:17:25.857Z
2023-10-06T03:17:25.857Z
merlin
<p>I've installed docker on Centos 7 from the official docker-ce repository (followed instructions <a href="https://docs.docker.com/engine/install/centos/" rel="nofollow noreferrer">here</a>). I'm seeing the following error when trying to start the docker service with <code>systemctl start docker</code></p>
<pre><code>Starting Docker Application Container Engine...
docker[24207]: unknown flag: --ip-forward
docker[24207]: See 'docker --help'.
docker[24207]: Usage:  docker [OPTIONS] COMMAND
</code></pre>
<p>Here is the docker version:</p>
<pre><code>[root@js03 englab]# docker --version
Docker version 24.0.6, build ed223bc
</code></pre>

<docker><containerd>
Docker on Centos 7 - "unkown flag: --ip-forward"
merlin
# Docker on Centos 7 - "unkown flag: --ip-forward"

(Asked by: username_0 on 2023-10-06)

I've installed docker on Centos 7 from the official docker-ce repository (followed instructions here). I'm seeing the following error when trying to start the docker service with systemctl start docker
Starting Docker Application Container Engine...
docker[24207]: unknown flag: --ip-forward
docker[24207]: See 'docker --help'.
docker[24207]: Usage:  docker [OPTIONS] COMMAND

Here is the docker version:
[root@js03 englab]# docker --version
Docker version 24.0.6, build ed223bc

**Tags:** docker, containerd


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## 1 answers

### Answer by username_0 on 2023-10-06. Score: 0 | Accepted answer

It turns out there was a leftover file from a previous version of docker at /etc/systemd/system/docker.service.d/service-overrides.conf that was injecting environment variables into the docker.service ExecStart command.
# cat /etc/systemd/system/docker.service.d/service-overrides.conf
[Service]
EnvironmentFile=-/etc/sysconfig/docker
EnvironmentFile=-/etc/sysconfig/docker-storage
EnvironmentFile=-/etc/sysconfig/docker-network
ExecStart=
ExecStart=/usr/bin/docker daemon $OPTIONS \
      $DOCKER_STORAGE_OPTIONS \
      $DOCKER_NETWORK_OPTIONS \
      $BLOCK_REGISTRY \
      $INSECURE_REGISTRY

I removed this file and rebooted, then docker started successfully.


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