docker 運行時常見錯誤
(1) Cannot connect to the Docker daemon at unix:///var/run/docker.sock.
[root@localhost geo]# docker version
Client: Docker Engine - Community
Version: 19.03.8
API version: 1.40
Go version: go1.12.17
Git commit: afacb8b
Built: Wed Mar 11 01:27:04 2020
OS/Arch: linux/amd64
Experimental: false
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docke r daemon running?
解決
systemctl daemon-reload
systemctl restart docker.service
# 或者
service docker restart
(2) Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock
[geo@localhost ~]$ docker version
Client: Docker Engine - Community
Version: 19.03.8
API version: 1.40
Go version: go1.12.17
Git commit: afacb8b
Built: Wed Mar 11 01:27:04 2020
OS/Arch: linux/amd64
Experimental: false
Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.40/version: dial unix /var/run/docker.sock: connect: permission denied
原因
摘自docker mannual上的一段話
Manage Docker as a non-root user
The docker daemon binds to a Unix socket instead of a TCP port. By default that Unix socket is owned by the user root and other users can only access it using sudo. The docker daemon always runs as the root user.
If you don’t want to use sudo when you use the docker command, create a Unix group called docker and add users to it. When the docker daemon starts, it makes the ownership of the Unix socket read/writable by the docker group.
大概的意思就是：docker進程使用Unix Socket而不是TCP端口。而默認情況下，Unix socket屬於root用戶，需要root權限才能訪問。
解決方法1
使用sudo獲取管理員權限，運行docker命令
解決方法2
docker守護進程啟動的時候，會默認賦予名字為docker的用戶組讀寫Unix socket的權限，因此只要創建docker用戶組，並將當前用戶加入到docker用戶組中，那么當前用戶就有權限訪問Unix socket了，進而也就可以執行docker相關命令
sudo groupadd docker #添加docker用戶組
sudo gpasswd -a $USER docker #將登陸用戶加入到docker用戶組中
newgrp docker #更新用戶組
docker ps #測試docker命令是否可以使用sudo正常使用