install docker on centos7 manually

1. download dock * .rpm

download the package whose version is depended on OS version website
docker-ce-18.03.0.ce-1.el7.centos.x86_64

2. install , start, and verify

before install docker, dependencies should be installed: pigz-2.3.3-1.el7.centos.x86_64.rpm ， container-selinux-2.107-3.el7.noarch.rpm then,
install docker :

sudo rpm -i docker-ce-18.03.0.ce-1.el7.centos.x86_64

start docker :

sudo systemctl start docker

verify :

sudo docker images ls 
...
sudo docker container ls 
...
sudo docker run hello-world
Hello from Docker!
This message shows that your installation appears to be working correctly.

3. ISSUE : warning: container-selinux-2.107-3.el7.noarch.rpm: Header V3 RSA/SHA256 Signature, key ID f4a80eb5: NOKEY

rpm uses Public Key Check to make installation more secure.

#use `lskeys` to see the signing keys installed 
$ lskeys 
#install a key with `rpm --import` followed by the key file(local file or a URL) 
$ rpm --import 
#disable GPG signature check for RPM packages
$ sudo rpm --nosignature  ****.rpm

reference :

[1] Thread: PROBLEM WITH "WARNING : NOKEY" WHILE INSTALLING A SOURCE RPM

[2] Rpm, Yum, Dnf “NOKEY” Public Key Check Error and Solution
[3] Install Docker Engine on CentOS