CoreOS主要包含以下一些東西：
（1）最小的OS：kernel+systemd
（2）使用Docker執行應用
（3）使用fleet管理叢集
（4）使用etcd實現服務發現：一個分散式的K/V儲存引擎儲存配置資料
下載vagrant的coreos配置檔案
$ git clone https://github.com/coreos/coreos-vagrant.git
$vagrant up
$ vagrant status
Current machine states:
core-01 running (virtualbox)
core-02 running (virtualbox)
core-03 running (virtualbox)
$ ssh-add ~/.vagrant.d/insecure_private_key
Identity added: /Users/yy/.vagrant.d/insecure_private_key (/Users/yy/.vagrant.d/insecure_private_key)
$ vagrant ssh core-01
Last login: Sun Sep 7 16:23:31 2014 from 10.0.2.2
CoreOS (beta)
core@core-01 ~ $ fleetctl list-machines
MACHINE IP METADATA
542a4130... 172.17.8.101 -
bcb90abf... 172.17.8.102 -
e6a8eaa9... 172.17.8.103 -
讀寫etcd
core@core-01 ~ $ etcdctl set first-etcd-key "Hello World"
Hello World
core@core-01 ~ $ etcdctl get first-etcd-key
Hello World
在core-02上可以讀到first-etcd-key對應的值：
core@core-02 ~ $ etcdctl get first-etcd-key
Hello World
也可以直接提供的API讀取相應的key：
core@core-02 ~ $ curl -L http://127.0.0.1:4001/v1/keys/first-etcd-key
{"action":"get","key":"/first-etcd-key","value":"Hello World","index":2264}
使用fleetctl管理服務
core@core-01 ~ $ cat hello.service
[Unit]
Description=My Service
After=docker.service
[Service]
TimeoutStartSec=0
ExecStartPre=-/usr/bin/docker kill hello
ExecStartPre=-/usr/bin/docker rm hello
ExecStartPre=/usr/bin/docker pull busybox
ExecStart=/usr/bin/docker run --name hello busybox /bin/sh -c "while true; do echo Hello World; sleep 1; done"
ExecStop=/usr/bin/docker stop hello
core@core-01 ~ $ fleetctl load hello.service
Job hello.service loaded on 542a4130.../172.17.8.101
core@core-01 ~ $ fleetctl start hello.service
Job hello.service launched on 542a4130.../172.17.8.101
檢視服務狀態
core@core-01 ~ $ fleetctl status hello.service
● hello.service - My Service
Loaded: loaded (/run/fleet/units/hello.service; linked-runtime)
Active: active (running) since Mon 2014-09-08 04:21:13 UTC; 1min 25s ago
Process: 1117 ExecStartPre=/usr/bin/docker pull busybox (code=exited, status=0/SUCCESS)
Process: 1108 ExecStartPre=/usr/bin/docker rm hello (code=exited, status=1/FAILURE)
Process: 1046 ExecStartPre=/usr/bin/docker kill hello (code=exited, status=1/FAILURE)
Main PID: 1185 (docker)
CGroup: /system.slice/hello.service
└─1185 /usr/bin/docker run --name hello busybox /bin/sh -c while true; do echo Hello World; sleep 1; done
Sep 08 04:22:28 core-01 docker[1185]: Hello World
Sep 08 04:22:29 core-01 docker[1185]: Hello World
Sep 08 04:22:30 core-01 docker[1185]: Hello World
Sep 08 04:22:31 core-01 docker[1185]: Hello World
Sep 08 04:22:32 core-01 docker[1185]: Hello World
Sep 08 04:22:33 core-01 docker[1185]: Hello World
Sep 08 04:22:34 core-01 docker[1185]: Hello World
Sep 08 04:22:35 core-01 docker[1185]: Hello World
Sep 08 04:22:36 core-01 docker[1185]: Hello World
Sep 08 04:22:37 core-01 docker[1185]: Hello World
core@core-01 ~ $ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
fa7084105f19 busybox:buildroot-2014.02 /bin/sh -c 'while tr 2 minutes ago Up 2 minutes hello
在另一個coreos檢視服務狀態
$ vagrant ssh core-02 -- -A
Last login: Mon Sep 8 04:35:40 2014 from 10.0.2.2
CoreOS (beta)
core@core-02 ~ $ fleetctl list-units
UNIT DSTATE TMACHINE STATE MACHINE ACTIVE
hello.service launched 542a4130.../172.17.8.101 launched 542a4130.../172.17.8.101 active
core@core-02 ~ $ fleetctl status hello.service
● hello.service - My Service
Loaded: loaded (/run/fleet/units/hello.service; linked-runtime)
Active: active (running) since Mon 2014-09-08 04:21:13 UTC; 15min ago
Process: 1117 ExecStartPre=/usr/bin/docker pull busybox (code=exited, status=0/SUCCESS)
Process: 1108 ExecStartPre=/usr/bin/docker rm hello (code=exited, status=1/FAILURE)
Process: 1046 ExecStartPre=/usr/bin/docker kill hello (code=exited, status=1/FAILURE)
Main PID: 1185 (docker)
CGroup: /system.slice/hello.service
└─1185 /usr/bin/docker run --name hello busybox /bin/sh -c while true; do echo Hello World; sleep 1; done
Sep 08 04:36:20 core-01 docker[1185]: Hello World
Sep 08 04:36:21 core-01 docker[1185]: Hello World
Sep 08 04:36:22 core-01 docker[1185]: Hello World
Sep 08 04:36:23 core-01 docker[1185]: Hello World
Sep 08 04:36:24 core-01 docker[1185]: Hello World
Sep 08 04:36:25 core-01 docker[1185]: Hello World
Sep 08 04:36:26 core-01 docker[1185]: Hello World
Sep 08 04:36:27 core-01 docker[1185]: Hello World
Sep 08 04:36:28 core-01 docker[1185]: Hello World
Sep 08 04:36:29 core-01 docker[1185]: Hello World
core@core-02 ~ $ fleetctl destroy hello.service
Destroyed hello.service
主要參考
[1] https://coreos.com/docs/quickstart/
作者：YY哥
出處：http://www.cnblogs.com/hustcat/
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