Docker - shawfdong/hyades GitHub Wiki
Docker is an open-source project that automates the deployment of applications inside software containers, by providing an additional layer of abstraction and automation of operating-system-level virtualization on Linux. Docker uses resource isolation features of the Linux kernel such as cgroups and kernel namespaces to allow independent containers to run within a single Linux instance, avoiding the overhead of starting virtual machines[1].
We'll install and test Docket on my CentOS 7 box[2].
Make sure firewalld is disabled and iptables is enabled:
# systemctl status firewalld # systemctl status iptables
Install Docker:
# yum -y install docker
Enable and start the Docker daemon:
# systemctl status docker.service
docker.service - Docker Application Container Engine
Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled)
Active: inactive (dead)
Docs: http://docs.docker.com
# systemctl enable docker.service
# systemctl start docker.service
Get the latest CentOS image:
# docker pull centos # docker images REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE docker.io/centos 7 fd44297e2ddb 6 days ago 215.7 MB docker.io/centos latest fd44297e2ddb 6 days ago 215.7 MB docker.io/centos centos7 fd44297e2ddb 6 days ago 215.7 MB
Test the CentOS image:
# docker run -i -t centos /bin/bash
[root@6935ebd5e6c9 /]# ls
bin dev etc home lib lib64 lost+found media mnt opt proc root run sbin srv sys tmp usr var
[root@6935ebd5e6c9 /]# uname -a
Linux 6935ebd5e6c9 3.10.0-229.1.2.el7.x86_64 #1 SMP Fri Mar 27 03:04:26 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
[root@6935ebd5e6c9 /]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
5: eth0: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
link/ether 02:42:ac:11:00:01 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::42:acff:fe11:1/64 scope link
valid_lft forever preferred_lft forever
Docker takes advantage of namespaces to provide the isolated workspace called container[3]. On the host:
# ip a
...
4: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
link/ether 56:84:7a:fe:97:99 brd ff:ff:ff:ff:ff:ff
inet 172.17.42.1/16 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::5484:7aff:fefe:9799/64 scope link
valid_lft forever preferred_lft forever
6: veth0388916: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP
link/ether 72:41:c5:d0:9e:95 brd ff:ff:ff:ff:ff:ff
inet6 fe80::7041:c5ff:fed0:9e95/64 scope link
valid_lft forever preferred_lft forever
# brctl show
bridge name bridge id STP enabled interfaces
docker0 8000.56847afe9799 no veth0388916