安装docker报错Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon？

Project scene:

Tip: When creating k8s with rancher, one of the servers reported Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

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Problem Description:

So I went to the server and checked the reason. Whether it was docker run helloworld or docker info, it reported Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
Then check the log

systemctl status docker

● docker.service - Docker Application Container Engine
   Loaded: loaded (/etc/systemd/system/docker.service; enabled; vendor preset: disabled)
   Active: activating (auto-restart) (Result: exit-code) since 四 2020-09-17 17:18:16 CST; 1s ago
     Docs: http://docs.docker.io
  Process: 6430 ExecStartPost=/sbin/iptables -I FORWARD -s 0.0.0.0/0 -j ACCEPT (code=exited, status=0/SUCCESS)
  Process: 6429 ExecStart=/opt/kube/bin/dockerd --registry-mirror=http://3cda3ca9.m.daocloud.io -H unix:///var/run/docker.sock -H tcp://0.0.0.0:2375 (code=exited, status=1/FAILURE)
 Main PID: 6429 (code=exited, status=1/FAILURE)

9月 17 17:18:16 cdh2-4 systemd[1]: Unit docker.service entered failed state.
9月 17 17:18:16 cdh2-4 systemd[1]: docker.service failed.

Look at the detailed log

journalctl -u docker.service

9月 08 21:12:32 cdh2-4 systemd[1]: Starting Docker Application Container Engine...
9月 08 21:12:32 cdh2-4 dockerd[17900]: time="2020-09-08T21:12:32.921547656+08:00" level=warning msg="could not change group /var/run/docker.sock to docker: group docker not found"
9月 08 21:12:32 cdh2-4 dockerd[17900]: time="2020-09-08T21:12:32.953783378+08:00" level=warning msg="failed to load plugin io.containerd.snapshotter.v1.btrfs" error="path /var/lib/docker/contain
9月 08 21:12:32 cdh2-4 dockerd[17900]: time="2020-09-08T21:12:32.956534309+08:00" level=warning msg="failed to load plugin io.containerd.snapshotter.v1.aufs" error="modprobe aufs failed: "modpro
9月 08 21:12:32 cdh2-4 dockerd[17900]: time="2020-09-08T21:12:32.957510869+08:00" level=warning msg="could not use snapshotter zfs in metadata plugin" error="path /var/lib/docker/containerd/daem
9月 08 21:12:32 cdh2-4 dockerd[17900]: time="2020-09-08T21:12:32.957525885+08:00" level=warning msg="could not use snapshotter btrfs in metadata plugin" error="path /var/lib/docker/containerd/da
9月 08 21:12:32 cdh2-4 dockerd[17900]: time="2020-09-08T21:12:32.957533745+08:00" level=warning msg="could not use snapshotter aufs in metadata plugin" error="modprobe aufs failed: "modprobe: FA
9月 08 21:12:33 cdh2-4 systemd[1]: Started Docker Application Container Engine.

Cause Analysis:

After repeated tossing, reinstalling, using different mirror sources, and using check-config.sh to check the configuration of the docker environment , according to the results of its scan, Baidu and Google solved some of the problems!

./check-config.sh 

其中出现 (RHEL7/CentOS7: User namespaces disabled; add 'user_namespace.enable=1' to boot command line)

solution:

groupadd docker
usermod -aG docker $(whoami)
service docker start

Solutions to other problems:

1. Run yum list installed | grep docker command, prompting that Repository epel is listed more than once in the configuration

solution:

zip centos7-repo.zip /etc/yum.repos.d/*

Back up the original configuration items and be prepared!

Universal solution:

cd /etc/yum.repos.d/
wget http://mirrors.aliyun.com/repo/Centos-7.repo
sed -i 's/^.*aliyuncs*/#&/g' /etc/yum.repos.d/CentOS-Base.repo
wget  https://mirrors.aliyun.com/repo/epel-7.repo

2. In centos7, docker info reports an error docker bridge-nf-call-iptables is disabled solution

solution:

cat > /etc/sysctl.d/docker.conf <<-'EOF'
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-arptables = 1
EOF

sysctl  --system
sysctl -p

3. Check which rpm docker has and kill it! 

yum list installed | grep docker
yum -y remove docker-ce-cli.x86_64
yum -y remove containerd.io.x86_64

 4. Back up /etc/docker/daemon.json. I have used many mirrors and tested a lot, but Ali is more reliable

cat >/etc/docker/daemon.json <<-'EOF'
{
  "registry-mirrors":["https://jnxt8d8b.mirror.aliyuncs.com"]
}
EOF

systemctl daemon-reload && systemctl restart docker

5. At this time, docker info

systemctl status docker
docker info

 

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solution:

Tip: docker reports an error Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon?
what can we do about it?

Encountered a bug, an occupational disease, and still refuse to let it go... This is a mistake, eat something, have a cup of coffee... I guess I'm crazy...

Take a look again

systemctl status docker

docker.service - Docker Application Container Engine
   Loaded: loaded (/etc/systemd/system/docker.service; disabled; vendor preset: disabled)
   Active: activating (auto-restart) (Result: exit-code) since 四 2020-09-17 17:49:59 CST; 466ms ago
     Docs: http://docs.docker.io
  Process: 15193 ExecStartPost=/sbin/iptables -I FORWARD -s 0.0.0.0/0 -j ACCEPT (code=exited, status=0/SUCCESS)
  Process: 15192 ExecStart=/opt/kube/bin/dockerd --registry-mirror=http://3cda3ca9.m.daocloud.io -H unix:///var/run/docker.sock -H tcp://0.0.0.0:2375 (code=exited, status=1/FAILURE)
 Main PID: 15192 (code=exited, status=1/FAILURE)

1. Remove --registry-mirror=http://3cda3ca9.m.daocloud.io

vim /etc/systemd/system/docker.service

I don’t know which blog to watch, I added it! After removing

[Unit]
Description=Docker Application Container Engine
Documentation=http://docs.docker.io

[Service]
Environment="PATH=/opt/kube/bin:/bin:/sbin:/usr/bin:/usr/sbin"
ExecStart=/opt/kube/bin/dockerd -H unix:///var/run/docker.sock -H tcp://0.0.0.0:2375
ExecStartPost=/sbin/iptables -I FORWARD -s 0.0.0.0/0 -j ACCEPT
ExecReload=/bin/kill -s HUP $MAINPID
Restart=always
RestartSec=5
LimitNOFILE=infinity
LimitNPROC=infinity
LimitCORE=infinity
Delegate=yes
KillMode=process

[Install]
WantedBy=multi-user.target

2，Cannot connect to the Docker daemon at tcp://0.0.0.0:2375. Is the docker daemon 

solution:

echo 'export DOCKER_HOST=tcp://0.0.0.0:2375' >> /etc/profile
source /etc/profile
systemctl daemon-reload && systemctl restart docker

Friendly link: https://www.cnblogs.com/weiyiming007/p/10168733.html

Finally, docker info, solve the problem!

docker info

systemctl status docker