物理機OS:
Ubuntu 12.04 3.8.0-42-generic x86_64
VirtualBox:
Oracle VM VirtualBox Manager 4.2.10
Vagrant:
Vagrant 1.7.3
CoreOS:
stable 717.3.0
coreos-vagrant source:
commit b9ed7e2182ff08b72419ab3e89f4a5652bc75082
一、原理
如果沒有Wall，CoreOS的coreos-vagrant安裝將非常簡單：
1、git clone https://github.com/coreos/coreos-vagrant
2、編輯配置文件
3、vagrant up
4、vagrant ssh
但是現在有了Wall，步驟3：vagrant up會報錯：無法連接到http://stable.release.core-os.net/amd64-usr/717.3.0/xx這個url，導致安裝失敗。
我大致分析了一下vagrant up的執行過程：
1、設置配置默認值
$num_instances = 1
$instance_name_prefix = "core"
$update_channel = "alpha"
$image_version = "current"
$enable_serial_logging = false
$share_home = false
$vm_gui = false
$vm_memory = 1024
$vm_cpus = 1
$shared_folders = {}
$forwarded_ports = {}
2、判斷是否存在config.rb這個配置，如果有，則加載。
3、設置config.vm.url，並獲取對應的json文件：
{
"name": "coreos-stable",
"description": "CoreOS stable",
"versions": [{
"version": "717.3.0",
"providers": [{
"name": "virtualbox",
"url": "http://stable.release.core-os.net/amd64-usr/717.3.0/coreos_production_vagrant.box",
"checksum_type": "sha256",
"checksum": "99dcd74c7cae8b1d90f108f8819f92b17bfbd34f4f141325bd0400fe4def55b6"
}]
}]
}
4、根據config.vm.provider（是virtualbox還是vmvare等）來決定采用哪種虛擬機創建邏輯。
這裡我們看到，整個過程只需要從core-os.net下載兩個文件：coreos_production_vagrant.box和coreos_production_vagrant.json。如果我們提前將這兩個文件下載到本地，並放在一個臨時的http server下，修改Vagrantfile和coreos_production_vagrant.json這兩個文件，就應該可以通過coreos-vagrant安裝了。
二、coreos-vagrant安裝single instance CoreOS
好了，根據上述原理，我們首先要下載coreos_production_vagrant.box和coreos_production_vagrant.json這兩個文件，根據我們的channel和版本選擇，兩個文件的下載地址分別為：
http://stable.release.core-os.net/amd64-usr/717.3.0/coreos_production_vagrant.box http://stable.release.core-os.net/amd64-usr/717.3.0/coreos_production_vagrant.json
接下來就是不管你用什麼梯子，只要把這兩個文件下載到本地，並放到一個目錄下就好了。
我們需要修改一下coreos_production_vagrant.json，將其中的url改為：
"url": "http://localhost:8080/coreos_production_vagrant.box"
我們要將這兩個文件放到一個local file server中，後續供core-vagrant訪問。最簡單的方法就是使用:
python -m SimpleHTTPServer 8080
當然使用Go實現一個簡單的http file server也是非常簡單的：
//fileserver.go
package main
import "net/http"
import "log"
func main() {
log.Fatal(http.ListenAndServe(":8080", http.FileServer(http.Dir("./"))))
}
接下來我們就可以按照正常步驟，下載coreos-vagrant並up了：
$git clone https://github.com/coreos/coreos-vagrant
修改Vagrantfile：
$ diff Vagrantfile Vagrantfile.bak 14,15c14,15 < $update_channel = "stable" < $image_version = "717.3.0" — > $update_channel = "alpha" > $image_version = "current" 55c55 < config.vm.box_url = "http://localhost:8080/coreos_production_vagrant.json" — > config.vm.box_url = "http://%s.release.core-os.net/amd64-usr/%s/coreos_production_vagrant.json" % [$update_channel, $image_version]
將user-data.sample改名為user-data，並編輯user-data，在etcd2下面增加一行：
etcd2:
name: core-01
將units:下面對於etcd2的注釋去掉，以enable etcd2服務。（將etcd服務注釋掉）
萬事俱備，只需vagrant up。
$ vagrant up
Bringing machine 'core-01' up with 'virtualbox' provider…
==> core-01: Box 'coreos-stable' could not be found. Attempting to find and install…
core-01: Box Provider: virtualbox
core-01: Box Version: 717.3.0
==> core-01: Loading metadata for box 'http://localhost:8080/coreos_production_vagrant.json'
core-01: URL: http://localhost:8080/coreos_production_vagrant.json
==> core-01: Adding box 'coreos-stable' (v717.3.0) for provider: virtualbox
core-01: Downloading: http://localhost:8080/coreos_production_vagrant.box
core-01: Calculating and comparing box checksum…
==> core-01: Successfully added box 'coreos-stable' (v717.3.0) for 'virtualbox'!
==> core-01: Importing base box 'coreos-stable'…
==> core-01: Matching MAC address for NAT networking…
==> core-01: Checking if box 'coreos-stable' is up to date…
==> core-01: Setting the name of the VM: coreos-vagrant_core-01_1437121834188_89503
==> core-01: Clearing any previously set network interfaces…
==> core-01: Preparing network interfaces based on configuration…
core-01: Adapter 1: nat
core-01: Adapter 2: hostonly
==> core-01: Forwarding ports…
core-01: 22 => 2222 (adapter 1)
==> core-01: Running 'pre-boot' VM customizations…
==> core-01: Booting VM…
==> core-01: Waiting for machine to boot. This may take a few minutes…
core-01: SSH address: 127.0.0.1:2222
core-01: SSH username: core
core-01: SSH auth method: private key
core-01: Warning: Connection timeout. Retrying…
==> core-01: Machine booted and ready!
==> core-01: Setting hostname…
==> core-01: Configuring and enabling network interfaces…
==> core-01: Running provisioner: file…
==> core-01: Running provisioner: shell…
core-01: Running: inline script
登入你的coreos實例：
$ vagrant ssh CoreOS stable (717.3.0) core@core-01 ~ $
在vagrant up時，你可能會遇到如下兩個錯誤：
錯誤1：
Progress state: VBOX_E_FILE_ERROR VBoxManage: error: Could not open the medium storage unit '/home1/tonybai/.vagrant.d/boxes/coreos-stable/717.3.0/virtualbox/coreos_production_vagrant_image.vmdk'. VBoxManage: error: VMDK: inconsistent references to grain directory in '/home1/tonybai/.vagrant.d/boxes/coreos-stable/717.3.0/virtualbox/coreos_production_vagrant_image.vmdk' (VERR_VD_VMDK_INVALID_HEADER).
這個問題的原因很可能是你的Virtualbox版本不對，比如版本太低，與coreos_production_vagrant.box格式不兼容。可嘗試安裝一下高版本virtualbox來解決。
錯誤2：
core-01: SSH address: 127.0.0.1:2222 core-01: SSH username: core core-01: SSH auth method: private key core-01: Warning: Connection timeout. Retrying… core-01: Warning: Connection timeout. Retrying… core-01: Warning: Connection timeout. Retrying…
coreos虛擬機創建後，似乎一直無法連接上。在coreos的github issue中，有人遇到了這個問題，目前給出的原因是因為cpu的支持虛擬化技術的vt開關沒有打開，需要在bios中將其開啟。這主要在安裝64bit box時才會發生。
到這裡，我們已經完成了一個single instance coreos虛擬機的安裝。vagrant halt可以幫助你將啟動的coreos虛擬機停下來。
$ vagrant halt ==> core-01: Attempting graceful shutdown of VM…
三、 CoreOS cluster
上面雖然成功的安裝了coreos，然並卵。在實際應用中，CoreOS多以Cluster形式呈現，也就是說我們要啟動多個CoreOS實例。
使用vagrant啟動多個coreos實例很簡單，只需將配置中的$num_instances從1改為n。
這裡我們啟用config.rb這個配置文件(將config.rb.sample改名為config.rb)，並將其中的$num_instances修改為3：
# Size of the CoreOS cluster created by Vagrant $num_instances=3
該配置文件中的數據會覆蓋Vagrantfile中的默認配置。
三個instance中的etcd2要想組成集群還需要一個配置修改，那就是在etcd.io上申請一個token：
$curl https://discovery.etcd.io/new https://discovery.etcd.io/fe81755687323aae273dc5f111eb059a
將這個token配置到user-data中的etcd2下：
etcd2:
#generate a new token for each unique cluster from https://discovery.etcd.io/new
#discovery: https://discovery.etcd.io/<token>
discovery: https://discovery.etcd.io/fe81755687323aae273dc5f111eb059a
我們再來up看看：
$ vagrant up
Bringing machine 'core-01' up with 'virtualbox' provider…
Bringing machine 'core-02' up with 'virtualbox' provider…
Bringing machine 'core-03' up with 'virtualbox' provider…
==> core-01: Checking if box 'coreos-stable' is up to date…
==> core-01: VirtualBox VM is already running.
==> core-02: Importing base box 'coreos-stable'…
==> core-02: Matching MAC address for NAT networking…
==> core-02: Checking if box 'coreos-stable' is up to date…
==> core-02: Setting the name of the VM: coreos-vagrant_core-02_1437388468647_96550
==> core-02: Fixed port collision for 22 => 2222. Now on port 2200.
==> core-02: Clearing any previously set network interfaces…
==> core-02: Preparing network interfaces based on configuration…
core-02: Adapter 1: nat
core-02: Adapter 2: hostonly
==> core-02: Forwarding ports…
core-02: 22 => 2200 (adapter 1)
==> core-02: Running 'pre-boot' VM customizations…
==> core-02: Booting VM…
==> core-02: Waiting for machine to boot. This may take a few minutes…
core-02: SSH address: 127.0.0.1:2200
core-02: SSH username: core
core-02: SSH auth method: private key
core-02: Warning: Connection timeout. Retrying…
==> core-02: Machine booted and ready!
==> core-02: Setting hostname…
==> core-02: Configuring and enabling network interfaces…
==> core-02: Running provisioner: file…
==> core-02: Running provisioner: shell…
core-02: Running: inline script
==> core-03: Importing base box 'coreos-stable'…
==> core-03: Matching MAC address for NAT networking…
==> core-03: Checking if box 'coreos-stable' is up to date…
==> core-03: Setting the name of the VM: coreos-vagrant_core-03_1437388512743_68112
==> core-03: Fixed port collision for 22 => 2222. Now on port 2201.
==> core-03: Clearing any previously set network interfaces…
==> core-03: Preparing network interfaces based on configuration…
core-03: Adapter 1: nat
core-03: Adapter 2: hostonly
==> core-03: Forwarding ports…
core-03: 22 => 2201 (adapter 1)
==> core-03: Running 'pre-boot' VM customizations…
==> core-03: Booting VM…
==> core-03: Waiting for machine to boot. This may take a few minutes…
core-03: SSH address: 127.0.0.1:2201
core-03: SSH username: core
core-03: SSH auth method: private key
core-03: Warning: Connection timeout. Retrying…
==> core-03: Machine booted and ready!
==> core-03: Setting hostname…
==> core-03: Configuring and enabling network interfaces…
==> core-03: Running provisioner: file…
==> core-03: Running provisioner: shell…
core-03: Running: inline script
$vagrant ssh core-02
CoreOS stable (717.3.0)
core@core-02 ~ $
可以看到Vagrant啟動了三個coreos instance。關閉這些instance，同樣用halt：
$ vagrant halt ==> core-03: Attempting graceful shutdown of VM… ==> core-02: Attempting graceful shutdown of VM… ==> core-01: Attempting graceful shutdown of VM…
四、小結
以上僅僅是CoreOS最基本的入門，雖然現在安裝ok了，但CoreOS的各種服務組件的功用、配置；如何與Docker配合形成分布式服務系統；如何用Google Kubernetes管理容器集群等還需更進一步深入學習，這個後續會慢慢道來。
原文：http://tonybai.com/2015/07/20/install-coreos-by-coreos-vagrant/