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本文小編為大家詳細介紹“CentOS7安裝Docker服務的方法”，內(nèi)容詳細，步驟清晰，細節(jié)處理妥當，希望這篇“CentOS7安裝Docker服務的方法”文章能幫助大家解決疑惑，下面跟著小編的思路慢慢深入，一起來學習新知識吧。
1.1、什么是docker？
docker是基于go語言實現(xiàn)的云開源項目，誕生于2013年初，最初發(fā)起者是dotcloud公司。
docker是一個開源的引擎，可以輕松的為任何應用創(chuàng)建一個輕量級的、可移植的、自給自足的容器。開發(fā)者在筆記本上編譯測試通過的容器可以批量地在生產(chǎn)環(huán)境中部署，包括vms（虛擬機）、bare metal、openstack 集群和其他的基礎應用平臺。
docker中文社區(qū)
docker的主要目標是'build,ship and run any app anywhere',即通過對應用組件的封裝（packing）、分發(fā)（distribution）、部署（deployment）、運行（runtime）等生命周期的管理，達到應用組件級別的“一次封裝，多次運行”。這里的應用組件，既可以是一個web應用，也可以是一套數(shù)據(jù)庫服務，甚至是一個操作系統(tǒng)或編輯器。
1.2、為什么要使用docker？
docker在正確的地點，正確的時間順應了正確的趨勢--即高效的構建應用。
更快速地的交付和部署。
更高效的資源利用
更輕松的更新部署
更簡單的更新管理
docker與虛擬機比較
docker容器很快，啟動和停止可以秒級實現(xiàn)，相比傳統(tǒng)的虛擬機方式快很多
docker容器對系統(tǒng)資源需求很少，一臺主機上面可以運行數(shù)千個docker容器
docker通過類似git的操作來方便用戶獲取、分布和更新應用鏡像，指令簡單，學習成本較低
docker通過dockerfile配置文件來支持靈活的自動化創(chuàng)建和部署機制，提高工作效率
1.3、虛擬化與docker
虛擬化是一個通用的概念，在不通領域有著不同的理解。在計算機領域，一般是指計算虛擬化（computing virtualization），或服務器虛擬化。
虛擬化的核心是對資源進行抽象，目標往往是為了在同一主機上運行多個操作系統(tǒng)或應用，從而提高系統(tǒng)資源的利用率，同時帶來降低成本，方便管理和容錯容災。
虛擬化可分為基于硬件的虛擬化和基于軟件的虛擬化。基于軟件的虛擬化又分為應用虛擬化和平臺虛擬化。平臺虛擬化又細分如下幾個子類：
完全虛擬化。虛擬機模擬完整的底層硬件環(huán)境和特權指令的執(zhí)行過程，客戶操作系統(tǒng)無需進行修改。例如vmware workstation，virtulbox，qemu等
硬件輔助虛擬化。利用硬件輔助支持處理敏感指令來實現(xiàn)完全虛擬化的功能，客戶端操作系統(tǒng)無需更改，例如xen，kvm等
部分虛擬化。只針對部分硬件資源進行虛擬化，客戶端操作系統(tǒng)需要進行更改。
超虛擬化。部分硬件接口以軟件的形式提供給客戶機操作系統(tǒng)，客戶機操作系統(tǒng)需要進行更改。
操作系統(tǒng)級虛擬化。內(nèi)核通過創(chuàng)建多個虛擬的操作系統(tǒng)實例來隔離不同的進程，docker技術。
docker 安裝
安裝docker是操作系統(tǒng)級虛擬化工具，它可以在containers中自動部署應用程序
安裝docker
[root@linuxprobe~]# yum -y install docker [root@linuxprobe~]# systemctl start docker [root@linuxprobe~]# systemctl enable docker [root@linuxprobe ~]# systemctl status docker # 查看docker狀態(tài) ● docker.service - docker application container engine loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor preset: disabled) active: active (running) since wed 2016-10-26 19:38:40 cst; 12s ago docs: http://docs.docker.com main pid: 3762 (docker-current) cgroup: /system.slice/docker.service └─3762 /usr/bin/docker-current daemon --exec-opt native.cgroupdriver=systemd --selinux-enabled --log-driver=journald oct 26 19:38:39 linuxprobe.org docker-current[3762]: time="2016-10-26t19:38:39.844803185+08:00" level=info msg="devmapper: successfully created filesystem xfs on device docker-253:0-104354176-base" oct 26 19:38:39 linuxprobe.org docker-current[3762]: time="2016-10-26t19:38:39.994708787+08:00" level=info msg="graph migration to content-addressability took 0.00 seconds" oct 26 19:38:40 linuxprobe.org docker-current[3762]: time="2016-10-26t19:38:40.018129400+08:00" level=info msg="firewalld running: true" oct 26 19:38:40 linuxprobe.org docker-current[3762]: time="2016-10-26t19:38:40.294869786+08:00" level=info msg="default bridge (docker0) is assigned with an ip address 172.17.0.0/16. daemon option --bip can ...red ip address" oct 26 19:38:40 linuxprobe.org docker-current[3762]: time="2016-10-26t19:38:40.567994904+08:00" level=info msg="loading containers: start." oct 26 19:38:40 linuxprobe.org docker-current[3762]: time="2016-10-26t19:38:40.568039413+08:00" level=info msg="loading containers: done." oct 26 19:38:40 linuxprobe.org docker-current[3762]: time="2016-10-26t19:38:40.568047306+08:00" level=info msg="daemon has completed initialization" oct 26 19:38:40 linuxprobe.org docker-current[3762]: time="2016-10-26t19:38:40.568058527+08:00" level=info msg="docker daemon" commit=cb079f6-unsupported execdriver=native-0.2 graphdriver=devicemapper version=1.10.3 oct 26 19:38:40 linuxprobe.org docker-current[3762]: time="2016-10-26t19:38:40.572491688+08:00" level=info msg="api listen on /var/run/docker.sock" oct 26 19:38:40 linuxprobe.org systemd[1]: started docker application container engine. hint: some lines were ellipsized, use -l to show in full.
下載官方鏡像并創(chuàng)建一個container，并在container中輸出“welcome to the docker world”
[root@linuxprobe ~]# docker pull centos using default tag: latest trying to pull repository docker.io/library/centos ... latest: pulling from docker.io/library/centos 08d48e6f1cff: pull complete digest: sha256:b2f9d1c0ff5f87a4743104d099a3d561002ac500db1b9bfa02a783a46e0d366c status: downloaded newer image for docker.io/centos:latest [root@linuxprobe ~]# docker run centos /bin/echo "welcome to the docker world" welcome to the docker world
使用“i”和“t”選項連接到container的交互會話，如下所示。如果從container會話退出，則container的進程完成
[root@linuxprobe ~]# docker run -i -t centos /bin/bash [root@82699d79557c /]# uname -a linux 82699d79557c 3.10.0-327.el7.x86_64 #1 smp thu nov 19 22:10:57 utc 2015 x86_64 x86_64 x86_64 gnu/linux [root@82699d79557c /]# exit exit [root@linuxprobe ~]# #back
如果從容器會話中退出并保持容器的進程，請按ctrl + p和ctrl + q鍵
[root@linuxprobe ~]# docker run -i -t centos /bin/bash [root@a05c7fd0a54f /]# [root@linuxprobe ~]# [root@linuxprobe ~]# docker ps container id image command created status ports names a05c7fd0a54f centos "/bin/bash" 24 seconds ago up 23 seconds trusting_fermat [root@linuxprobe ~]# docker attach a05c7fd0a54f # connect docekr process [root@a05c7fd0a54f /]# [root@linuxprobe ~]# docker kill a05c7fd0a54f # kill docker process a05c7fd0a54f [root@linuxprobe ~]# docker ps # 查看運行的docker服務 container id image command created status ports names
docker：添加鏡像
在容器中添加鏡像文件
例如，使用更新官方映像安裝httpd，并將其添加為容器的新映像。該容器是在每次執(zhí)行docker run命令時生成的，因此添加最新執(zhí)行的容器如下
[root@linuxprobe ~]# docker images repository tag image id created size docker.io/centos latest 0584b3d2cf6d less than a second ago 196.5 mb # start a container and install httpd [root@linuxprobe ~]# docker run centos /bin/bash -c "yum -y update; yum -y install httpd" [root@linuxprobe ~]# docker ps -a | head -2 container id image command created status ports names f36383194ad4 centos "/bin/bash -c 'yum -y" 2 minutes ago exited (0) 45 seconds ago jolly_cray elegant_wright [root@linuxprobe ~]# docker commit f36383194ad4 my_image/centos_httpd [root@linuxprobe ~]# docker images repository tag image id created size docker.io/centos latest 0584b3d2cf6d less than a second ago 196.5 mb my_image/centos_httpd latest b0be2940865a 7 seconds ago 338.3 mb
訪問容器
root@linuxprobe ~]# docker run -it -p 8081:80 my_image/centos_httpd /bin/bash [root@2f0d06526d42 /]# /usr/sbin/httpd & [1] 14 [root@2f0d06526d42 /]# ah00558: httpd: could not reliably determine the server's fully qualified domain name, using 172.17.0.2. set the 'servername' directive globally to suppress this message [1]+ done /usr/sbin/httpd [root@2f0d06526d42 /]# echo "httpd on docker container" > /var/www/html/index.html # exit with ctrl+p, ctrl+q [root@2f0d06526d42 /]# [root@linuxprobe ~]# docker ps container id image command created status ports names 2f0d06526d42 my_image/centos_httpd "/bin/bash" 54 seconds ago up 52 seconds 0.0.0.0:8081->80/tcp hopeful_gates [root@linuxprobe ~]# docker ps -a | head -2 container id image command created status ports names 2f0d06526d42 my_image/centos_httpd "/bin/bash" 27 minutes ago up 27 minutes 0.0.0.0:8081->80/tcp hopeful_gates
客戶端瀏覽器訪問
docker：使用dockerfile
使用dockerfile并自動創(chuàng)建docker鏡像
[1] dockerfile的格式是[instruction arguments],請參閱instruction的以下說明。
instruction 說明
maintainer 它設置生成的圖像的作者字段。
run 當創(chuàng)建docker鏡像時，它將執(zhí)行任何命令。
cmd 它將執(zhí)行任何命令當docker容器將被執(zhí)行。
label 它向圖像添加元數(shù)據(jù)。
expose 它通知docker容器將在運行時偵聽指定的網(wǎng)絡端口。
add 它復制新文件，目錄或遠程文件url。
copy 它復制新的文件或目錄。 [add]的區(qū)別是，它不可能指定remore url，也不會自動提取歸檔文件。
volume 它創(chuàng)建具有指定名稱的裝入點，并將其標記為從本機主機或其他容器保存外部裝入的卷 user它設置用戶名或uid。
workdir 它設置工作目錄。
例如，創(chuàng)建一個dockerfile來安裝httpd并添加index.html，并使用80端口啟動httpd
[root@linuxprobe ~]# vim dockerfile # create new from centos maintainer linuxprobe <admin@linuxprobe.org> run yum -y install httpd run echo "hello linuxprobe dockerfile" > /var/www/html/index.html expose 80 cmd ["-d", "foreground"] entrypoint ["/usr/sbin/httpd"] [root@linuxprobe ~]# docker build -t web_server:latest . sending build context to docker daemon 21.5 kb step 1 : from centos ---> 0584b3d2cf6d step 2 : maintainer linuxprobe <admin@linuxprobe.org> ---> running in 8064d0091e44 ---> 940c8fbe4161 removing intermediate container 8064d0091e44 step 3 : run yum -y install httpd ---> running in 3d37e4919fa9 loaded plugins: fastestmirror, ovl determining fastest mirrors * base: mirrors.163.com * extras: ftp.sjtu.edu.cn * updates: mirrors.163.com resolving dependencies --> running transaction check ---> package httpd.x86_64 0:2.4.6-40.el7.centos.4 will be installed --> processing dependency: httpd-tools = 2.4.6-40.el7.centos.4 for package: httpd-2.4.6-40.el7.centos.4.x86_64 --> processing dependency: system-logos >= 7.92.1-1 for package: httpd-2.4.6-40.el7.centos.4.x86_64 --> processing dependency: /etc/mime.types for package: httpd-2.4.6-40.el7.centos.4.x86_64 --> processing dependency: libaprutil-1.so.0()(64bit) for package: httpd-2.4.6-40.el7.centos.4.x86_64 --> processing dependency: libapr-1.so.0()(64bit) for package: httpd-2.4.6-40.el7.centos.4.x86_64 --> running transaction check ---> package apr.x86_64 0:1.4.8-3.el7 will be installed ---> package apr-util.x86_64 0:1.5.2-6.el7 will be installed ---> package centos-logos.noarch 0:70.0.6-3.el7.centos will be installed ---> package httpd-tools.x86_64 0:2.4.6-40.el7.centos.4 will be installed ---> package mailcap.noarch 0:2.1.41-2.el7 will be installed --> finished dependency resolution dependencies resolved ================================================================================ package arch version repository size ================================================================================ installing: httpd x86_64 2.4.6-40.el7.centos.4 updates 2.7 m installing for dependencies: apr x86_64 1.4.8-3.el7 base 103 k apr-util x86_64 1.5.2-6.el7 base 92 k centos-logos noarch 70.0.6-3.el7.centos base 21 m httpd-tools x86_64 2.4.6-40.el7.centos.4 updates 83 k mailcap noarch 2.1.41-2.el7 base 31 k transaction summary ================================================================================ install 1 package (+5 dependent packages) total download size: 24 m installed size: 31 m downloading packages: warning: /var/cache/yum/x86_64/7/base/packages/apr-util-1.5.2-6.el7.x86_64.rpm: header v3 rsa/sha256 signature, key id f4a80eb5: nokey public key for apr-util-1.5.2-6.el7.x86_64.rpm is not installed public key for httpd-tools-2.4.6-40.el7.centos.4.x86_64.rpm is not installed -------------------------------------------------------------------------------- total 382 kb/s | 24 mb 01:05 retrieving key from file:///etc/pki/rpm-gpg/rpm-gpg-key-centos-7 importing gpg key 0xf4a80eb5: userid : "centos-7 key (centos 7 official signing key) <security@centos.org>" fingerprint: 6341 ab27 53d7 8a78 a7c2 7bb1 24c6 a8a7 f4a8 0eb5 package : centos-release-7-2.1511.el7.centos.2.10.x86_64 (@centos) from : /etc/pki/rpm-gpg/rpm-gpg-key-centos-7 running transaction check running transaction test transaction test succeeded running transaction installing : apr-1.4.8-3.el7.x86_64 1/6 installing : apr-util-1.5.2-6.el7.x86_64 2/6 installing : httpd-tools-2.4.6-40.el7.centos.4.x86_64 3/6 installing : centos-logos-70.0.6-3.el7.centos.noarch 4/6 installing : mailcap-2.1.41-2.el7.noarch 5/6 installing : httpd-2.4.6-40.el7.centos.4.x86_64 6/6 verifying : apr-1.4.8-3.el7.x86_64 1/6 verifying : httpd-tools-2.4.6-40.el7.centos.4.x86_64 2/6 verifying : apr-util-1.5.2-6.el7.x86_64 3/6 verifying : httpd-2.4.6-40.el7.centos.4.x86_64 4/6 verifying : mailcap-2.1.41-2.el7.noarch 5/6 verifying : centos-logos-70.0.6-3.el7.centos.noarch 6/6 installed: httpd.x86_64 0:2.4.6-40.el7.centos.4 dependency installed: apr.x86_64 0:1.4.8-3.el7 apr-util.x86_64 0:1.5.2-6.el7 centos-logos.noarch 0:70.0.6-3.el7.centos httpd-tools.x86_64 0:2.4.6-40.el7.centos.4 mailcap.noarch 0:2.1.41-2.el7 complete! ---> 3ce9abf4dfea removing intermediate container 3d37e4919fa9 step 4 : run echo "hello linuxprobe dockerfile" > /var/www/html/index.html ---> running in 297d8d666c8d ---> 3d185363045b removing intermediate container 297d8d666c8d step 5 : expose 80 ---> running in 017db517e06a ---> 5c855e478c3c removing intermediate container 017db517e06a step 6 : cmd -d foreground ---> running in 6add13fca3cb ---> 7a219d9fa6e1 removing intermediate container 6add13fca3cb step 7 : entrypoint /usr/sbin/httpd ---> running in da4671709ee1 ---> c0d84e256068 removing intermediate container da4671709ee1 successfully built c0d84e256068 [root@linuxprobe ~]# docker images repository tag image id created size docker.io/centos latest 0584b3d2cf6d less than a second ago 196.5 mb web_server latest c0d84e256068 36 seconds ago 338.3 mb my_image/centos_httpd latest b0be2940865a 4 hours ago 338.3 mb [root@linuxprobe ~]# docker run -d -p 80:80 web_server c37d25a405a8e0599bf54fe77d78c807a520242a21ccb15b18d6b6ee4d13415b [root@linuxprobe ~]# docker ps container id image command created status ports names c37d25a405a8 web_server "/usr/sbin/httpd -d f" 6 seconds ago up 5 seconds 0.0.0.0:80->80/tcp condescending_knuth 2f0d06526d42 my_image/centos_httpd "/bin/bash" about an hour ago up about an hour 0.0.0.0:8081->80/tcp hopeful_gat
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