Experience Docker

Docker 這東西我注意很久了，但一直以為他就一個 VM Guest Machine 的 Adapter 之類的東西，然後可以 remote 一些指令。不過我誤解了，因為如果只是這樣，應該紅不起來。看到這本書 Docker —— 從入門到實踐裡面提到一段和 VM 的比較，如下圖節錄：

這段很吸引我，我想『感覺』一下啟動的『秒級』是啥感覺，還有效能接近『原生』。。。這太有吸引力了！！然後還是可以快速建立測試環境，也符合我現在想要的，甚至可以不用像 OpenStack 那麼複雜的安裝和設置，而且要很多 resource (就是機器要很強啦) 。。。

以下是我的感動筆記。。。。 XDD

Enviornment

OS X (10.10)
Boot2Docker
- Mac OS: Boot2Docker 1.4.1
- Windows 可以下載 Windows-installer

Install

直接安裝下載的 Boot2Docker-1.4.1.pkg, 跟一般在 Mac 上安裝軟體一樣

到 LaunchPad 點選 boot2docker, 會開始初始化, 我的過程如下, 看起來應該沒問題:

init boot2docker

rick@iWish:22:39:27 ~$ bash
unset DYLD_LIBRARY_PATH ; unset LD_LIBRARY_PATH
mkdir -p ~/.boot2docker
if [ ! -f ~/.boot2docker/boot2docker.iso ]; then cp /usr/local/share/boot2docker/boot2docker.iso ~/.boot2docker/ ; fi
/usr/local/bin/boot2docker init
/usr/local/bin/boot2docker up
$(/usr/local/bin/boot2docker shellinit)
docker version
rick@iWish:22:39:27 ~$ unset DYLD_LIBRARY_PATH ; unset LD_LIBRARY_PATH
rick@iWish:22:39:27 ~$ mkdir -p ~/.boot2docker
ocker.iso ~/.boot2docker/ ; fi-f ~/.boot2docker/boot2docker.iso ]; then cp /usr/local/share/boot2docker/boot2d
rick@iWish:22:39:27 ~$ /usr/local/bin/boot2docker init
Generating public/private rsa key pair.
... omitted ...
rick@iWish:22:40:11 ~$ docker version
Client version: 1.4.1
Client API version: 1.16
Go version (client): go1.3.3
Git commit (client): 5bc2ff8
OS/Arch (client): darwin/amd64
Server version: 1.4.1
Server API version: 1.16
Go version (server): go1.3.3
Git commit (server): 5bc2ff8
rick@iWish:22:40:12 ~$

Install Image from Docker Hub - CentOS

我習慣使用 CentOS，就先來一個漱漱口，指令：docker pull centos。Docker 會到一個叫做 Docker Hub 的地方抓指定的 image，Docker Hub 上有很多各式各樣的映像檔分類。以下是我抓的過程：

docker pull centos

rick@iWish:22:40:12 ~$ docker pull centos
centos:latest: The image you are pulling has been verified
511136ea3c5a: Pull complete
5b12ef8fd570: Pull complete
34943839435d: Pull complete
Status: Downloaded newer image for centos:latest

這個過程會抓到的是最新的 CentOS 7，如果想要指定版本，那就要下 docker pull centos:centos6

Run command in CentOS

docker run 是用來執行 container 裏的程式，後面可以帶參數，跑完後 container 就結束了，我執行幾個 linux command：

rick@iWish:23:19:44 ~$ docker run centos /bin/echo 'hello'
hello
rick@iWish:23:19:56 ~$ docker run centos /bin/cat /etc/issue
\S
Kernel \r on an \m

rick@iWish:23:22:41 ~$ docker run centos /bin/cat /etc/fstab
LABEL=_/   /        ext4      defaults         0 0
devpts     /dev/pts  devpts  gid=5,mode=620   0 0
tmpfs      /dev/shm  tmpfs   defaults         0 0
proc       /proc     proc    defaults         0 0
sysfs      /sys      sysfs   defaults         0 0
rick@iWish:23:22:47 ~$ docker run centos /bin/df
Filesystem     1K-blocks   Used Available Use% Mounted on
rootfs          19049892 310512  17748656   2% /
none            19049892 310512  17748656   2% /
tmpfs            1028332      0   1028332   0% /dev
shm                65536      0     65536   0% /dev/shm
/dev/sda1       19049892 310512  17748656   2% /etc/hosts
tmpfs            1028332      0   1028332   0% /proc/kcore

可以這樣想像，guest machine 不用真的開起來，然後就可以執行 container 裡面的程式。如果想開啟 shell：docker run -t -i centos /bin/bash，-t 是虛擬終端機，-i 是開啟 stdin，如下：

rick@iWish:23:28:15 ~$ docker run -t -i centos
[root@983b17e4470a /]# pwd
/
[root@983b17e4470a /]# ls -ls
total 52
0 lrwxrwxrwx  1 root root    7 Dec  2 14:58 bin -> usr/bin
0 drwxr-xr-x  5 root root  380 Dec 17 15:28 dev
4 drwxr-xr-x 46 root root 4096 Dec 17 15:28 etc
4 drwxr-xr-x  2 root root 4096 Jun 10  2014 home
0 lrwxrwxrwx  1 root root    7 Dec  2 14:58 lib -> usr/lib
0 lrwxrwxrwx  1 root root    9 Dec  2 14:58 lib64 -> usr/lib64
4 drwx------  2 root root 4096 Dec  2 14:58 lost+found
4 drwxr-xr-x  2 root root 4096 Jun 10  2014 media
4 drwxr-xr-x  2 root root 4096 Jun 10  2014 mnt
4 drwxr-xr-x  2 root root 4096 Jun 10  2014 opt
0 dr-xr-xr-x 93 root root    0 Dec 17 15:28 proc
4 dr-xr-x---  2 root root 4096 Dec  2 15:00 root
4 drwxr-xr-x  7 root root 4096 Dec  2 15:00 run
0 lrwxrwxrwx  1 root root    8 Dec  2 14:58 sbin -> usr/sbin
4 drwxr-xr-x  3 root root 4096 Dec  2 15:00 selinux
4 drwxr-xr-x  2 root root 4096 Jun 10  2014 srv
0 dr-xr-xr-x 13 root root    0 Dec 17 15:28 sys
4 drwxrwxrwt  2 root root 4096 Dec 17 15:28 tmp
4 drwxr-xr-x 13 root root 4096 Dec  2 14:58 usr
4 drwxr-xr-x 18 root root 4096 Dec  2 14:59 var
[root@983b17e4470a /]# df -h
Filesystem      Size  Used Avail Use% Mounted on
rootfs           19G  305M   17G   2% /
none             19G  305M   17G   2% /
tmpfs          1005M     0 1005M   0% /dev
shm              64M     0   64M   0% /dev/shm
/dev/sda1        19G  305M   17G   2% /etc/hosts
tmpfs          1005M     0 1005M   0% /proc/kcore
[root@983b17e4470a /]# uname -a
Linux 983b17e4470a 3.16.7-tinycore64 #1 SMP Tue Dec 16 23:03:39 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
[root@983b17e4470a /]# whoami
root
[root@983b17e4470a /]# netstat -na
bash: netstat: command not found
[root@983b17e4470a /]# ifconfig
bash: ifconfig: command not found
[root@983b17e4470a home]# exit
exit
rick@iWish:23:33:43 ~$

試了一些基本的東西，看看系統狀態，不過可以發現 netstat、ifconfig 都無法執行，應該需要額外設置 eth 之類的東西吧。

LAMP

我最常用的 LAMP 組合，找了適當的 image 裝: docker pull dockerfiles/centos-lamp
也可以先用 docker search [keyword] 找找看，下面是搜尋的結果 - 一堆

rick@iWish:23:33:45 ~$ docker search lamp
NAME                                         DESCRIPTION                                     STARS     OFFICIAL   AUTOMATED
tutum/lamp                                   LAMP image - Apache listens in port 80, an...   41                   [OK]
dockerfiles/centos-lamp                                                                      6                    [OK]
tehes/superdevlamp                           Complete optimized LAMP stack for Drupal d...   4
ricardoamaro/drupal-lamp                     https://github.com/ricardoamaro/docker-dru...   4
rpawel/lamp55-joomla                                                                         3
... 太多了，省略 ...
# 下載
rick@iWish:23:43:29 ~$ docker pull dockerfiles/centos-lamp
Pulling repository dockerfiles/centos-lamp
666d59f8429d: Download complete
539c0211cd76: Download complete
1b522efc5462: Download complete
46d50bbca148: Download complete
082a6a05108d: Download complete
f1c190401f1a: Download complete
987fe7539090: Download complete
7bfe4ff4df41: Download complete
720bdd4ad932: Download complete
27a235cf3931: Download complete
837dfe4536e0: Download complete
f977418995c6: Download complete
d638bd947021: Download complete
dc5d255a48c7: Download complete
b1089d528d27: Download complete
bc3211f4cc3e: Download complete
62d8c4d27eed: Download complete
Status: Downloaded newer image for dockerfiles/centos-lamp:latest

參數 -d 是啟動成 daemon。接續的 -p 49001:80 是指定和 local machine port mapping: 49001 對應到 80

start daemon

1 2	rick@iWish:23:56:40 ~$ docker run -d -p 49001:80 dockerfiles/centos-lamp aef450a7b2092b0a5699e23bf48a01766ca2d6b9e08741f11864510aa326097c

檢查 Daemon 狀態：

docker ps

rick@iWish:23:57:34 ~$ docker ps
CONTAINER ID        IMAGE                            COMMAND             CREATED             STATUS              PORTS                           NAMES
aef450a7b209        dockerfiles/centos-lamp:latest   "supervisord -n"    21 seconds ago      Up 21 seconds       22/tcp, 0.0.0.0:49001->80/tcp   stoic_franklin
rick@iWish:23:59:29 ~$

打開瀏覽器，開啟 URL: http://localhost:49001 應該會看到 apache 的畫面 不過其實我沒跑成功, 待研究

結論

『感覺』過後，其實還不賴！真的『秒殺』的啟動時間。接下來我還想繼續是一些東西，像是：

MySQL, MongoDB, Memcache
Java Container: Tomcat / Jetty
Multiple docker container
Config network for docker container
Docker life-cycle
How to backup? portable?

如果跟我同樣再觀望，可以去官方的 Try It! 先試看看。

Experience Docker

Enviornment

Install

Install Image from Docker Hub - CentOS

Run command in CentOS

LAMP

結論

延伸閱讀

Reference

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