How to start Docker Daemon, "dockerd", on CentOS systems?

If you have installed Docker on your CentOS system, you follow these steps to start the Docker Daemon, "dockerd".

1. Verify Docker installation path.

fyicenter$ which dockerd
  /usr/bin/dockerd

2. Start Docker Daemon using the "dockerd" command. But it needs "root" permission. It still fails to start Container Daemon.

fyicenter$ dockerd
  INFO[09:51:59.778175452+08:00] Starting up
  dockerd needs to be started with root.
  To see how to run dockerd in rootless mode with unprivileged user,
  see the documentation

fyicenter$ sudo dockerd &
INFO[...] Starting up
WARN[...] could not change group /var/run/docker.sock to docker: group docker not found
INFO[...] parsed scheme: "unix"                         module=grpc
INFO[...] scheme "unix" not registered, fallback to default scheme  module=grpc
INFO[...] ClientConn switching balancer to "pick_first"  module=grpc
WARN[...] grpc: addrConn.createTransport failed to connect
  to {unix:///run/containerd/containerd.sock <nil> 0 <nil>}.
  Err :connection error: desc = "transport: Error while dialing
  dial unix /run/containerd/containerd.sock: connect: connection refused".
  Reconnecting...  module=grpc

3. Log in as "root" and start Docker Daemon again.

fyicenter# dockerd &

INFO[...] Starting up
WARN[...] could not change group /var/run/docker.sock to docker: group docker not found
INFO[...] libcontainerd: started new containerd process  pid=3145420
INFO[...] parsed scheme: "unix"                         module=grpc
INFO[...] scheme "unix" not registered, fallback to default scheme  module=grpc
INFO[...] ClientConn switching balancer to "pick_first"  module=grpc
INFO[...] starting containerd version=v1.4.6
INFO[...] loading plugin "io.containerd.content.v1.content"...  type=io.containerd.content.v1
INFO[...] loading plugin "io.containerd.snapshotter.v1.aufs"...  type=io.containerd.snapshotter.v1
INFO[...] serving... address=/var/run/docker/containerd/containerd-debug.sock
INFO[...] serving... address=/var/run/docker/containerd/containerd.sock.ttrpc
INFO[...] serving... address=/var/run/docker/containerd/containerd.sock
INFO[...] containerd successfully booted in 0.023700s
INFO[...] using prior storage driver: overlay2
WARN[...] Your kernel does not support cgroup blkio weight
WARN[...] Your kernel does not support cgroup blkio weight_device
INFO[...] Loading containers: start.
INFO[...] Firewalld: docker zone already exists, returning
INFO[...] Firewalld: interface docker0 already part of docker zone, returning
INFO[...] Firewalld: interface docker0 already part of docker zone, returning
INFO[...] Default bridge (docker0) is assigned with an IP address 172.17.0.0/16. Daemon option --bip can be used to set a preferred IP address
INFO[...] Firewalld: interface docker0 already part of docker zone, returning
INFO[...] Loading containers: done.
INFO[...] Docker daemon commit=b0f5bc3 graphdriver(s)=overlay2 version=20.10.7
INFO[...] Daemon has completed initialization
INFO[...] API listen on /var/run/docker.sock

4. Verify Docker Daemon.

fyicenter$ sudo ps -efl | grep docker
  - 264001 -     12:24 pts/14   00:00:00 dockerd
  - 275268 -     12:24 ?        00:00:00 containerd --config \
    /var/run/docker/containerd/containerd.toml --log-level info

fyicenter$ sudo docker info
  Client:
   Context:    default
   Debug Mode: false

  Server:
   Containers: 0
    Running: 0
    Paused: 0
    Stopped: 0
   Images: 0
   Server Version: 20.10.7
   Storage Driver: overlay2
    Backing Filesystem: xfs
  ...

5. Possible issue when starting the Docker binary package is the $PATH access to the "containerd" command. You need to add the "./docker" directory to $PATH.

fyicenter$ su

fyicenter# ./docker/dockerd
  INFO[09:53:51.388587173+08:00] Starting up
  failed to start containerd: exec: "containerd":
    executable file not found in $PATH

fyicenter# export PATH=/home/fyicenter/docker:$PATH

fyicenter# ./docker/dockerd
  ...
  INFO[...] starting containerd version=v1.4.6
  INFO[...] containerd successfully booted in 0.023700s
  INFO[...] Docker daemon commit=b0f5bc3 graphdriver(s)=overlay2 version=20.10.7
  INFO[...] Daemon has completed initialization
  INFO[...] API listen on /var/run/docker.sock

⇒ Install Docker CE on Ubuntu

⇐ Install Docker CE Binary on CentOS

⇑ Install Docker CE on CentOS

⇑⇑ Docker Container Platform - Tutorials