在我的例子中，是进程本身(CI服务器代理)试图运行一个docker命令，但无法运行它，但当我试图从同一个用户中运行相同的命令时，它工作了。

重新启动运行CI服务器代理的守护进程解决了这个问题。

之前命令在代理内部无法工作的原因是因为代理在我安装docker并授予docker组权限之前正在运行，代理进程使用缓存的旧权限并且正在失败。重新启动进程将丢弃缓存，使事情得以解决。

添加docker组

$ sudo groupadd docker

将当前用户添加到docker组

$ sudo usermod -aG docker $USER

切换会话到docker组

$ newgrp - docker

运行一个示例进行测试

$ docker run hello-world

在Linux环境下，安装docker后，需要重新启动docker才能更好地避免这个问题。

$ sudo systemctl restart docker

在Centos上安装Docker后。在运行下面的命令时，我得到下面的错误。

[centos@aiops-dev-cassandra3 ~]$ docker run hello-world
docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.soc k/v1.40/containers/create: dial unix /var/run/docker.sock: connect: permission denied.
See 'docker run --help'.

修改docker.socket的Group和Permission

[centos@aiops-dev-cassandra3 ~]$ ls -l /lib/systemd/system/docker.socket
-rw-r--r--. 1 root root 197 Nov 13 07:25 /lib/systemd/system/docker.socket
[centos@aiops-dev-cassandra3 ~]$ sudo chgrp docker /lib/systemd/system/docker.socket
[centos@aiops-dev-cassandra3 ~]$ sudo chmod 666 /var/run/docker.sock
[centos@aiops-dev-cassandra3 ~]$ ls -lrth /var/run/docker.sock
srw-rw-rw-. 1 root docker 0 Nov 20 11:59 /var/run/docker.sock
[centos@aiops-dev-cassandra3 ~]$

使用以下docker命令进行验证

[centos@aiops-dev-cassandra3 ~]$ docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
1b930d010525: Pull complete
Digest: sha256:c3b4ada4687bbaa170745b3e4dd8ac3f194ca95b2d0518b417fb47e5879d9b5f
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

[centos@aiops-dev-cassandra3 ~]$

Docker守护进程绑定到Unix套接字，而不是TCP端口。 默认情况下，Unix套接字由root用户拥有，其他用户只能使用sudo访问它。Docker守护进程始终以根用户运行。

如果不想在docker命令前面加上sudo，可以创建一个名为docker的Unix组，并向其中添加用户。当Docker守护进程启动时，它会创建一个Unix套接字，供Docker组的成员访问。

创建docker组并添加用户:

Create the docker group sudo groupadd docker Add your user to the docker group sudo usermod -aG docker $USER Log out and log back in so that your group membership is re-evaluated. If testing on a virtual machine, it may be necessary to restart the virtual machine for changes to take effect. On a desktop Linux environment such as X Windows, log out of your session completely and then log back in. On Linux, you can also run the following command to activate the changes to groups: newgrp docker Verify that you can run docker commands without sudo. The below command downloads a test image and runs it in a container. When the container runs, it prints an informational message and exits docker run hello-world

如果您在将用户添加到Docker组之前首先使用sudo运行Docker CLI命令，您可能会看到以下错误，这表明您的~/。由于sudo命令，创建的Docker /目录权限不正确。

   WARNING: Error loading config file: /home/user/.docker/config.json -
   stat /home/user/.docker/config.json: permission denied

要解决这个问题，要么删除~/。Docker /目录(它会自动重新创建，但任何自定义设置都将丢失)，或使用以下命令更改其所有权和权限:

sudo chown "$USER":"$USER" /home/"$USER"/.docker -R

sudo chmod g+rwx "$HOME/.docker" -R

linux上docker的所有其他后期安装步骤都可以在这里找到https://docs.docker.com/engine/install/linux-postinstall/

这对我来说很有用:

进入容器内部并修改文件的ACL

sudo usermod -aG docker $USER
sudo setfacl --modify user:$USER:rw /var/run/docker.sock

这是一个比使用chmod更好的解决方案。