This message shows that your installation appears to be working correctly.<\/div>
…<\/div> <\/div>\n
As you may tell from the output, docker<\/code> was initially unable to find the hello-world<\/code> image locally, so it downloaded it from Docker Hub, created a container from it, and ran the application within the container, which displayed the Hello from Docker [...]<\/code> message.<\/p>\nSearching for Docker Images<\/h3>\n
You can also search for various images, using the search<\/code> subcommand. The script will search Docker Hub and list all images matching the string you used:<\/p>\n$ sudo docker search wordpress<\/code><\/pre>\nOutput<\/small><\/p>\n$ sudo docker search wordpress\nNAME DESCRIPTION STARS OFFICIAL AUTOMATED\nwordpress The WordPress rich content management system\u2026 2652 [OK] \nbitnami\/wordpress Bitnami Docker Image for WordPress 95 [OK]\nappcontainers\/wordpress Centos\/Debian Based Customizable WordPress C\u2026 34 [OK]\netopian\/alpine-php-wordpress Alpine WordPress Nginx PHP-FPM WP-CLI 18 [OK]\ncenturylink\/wordpress WordPress image with MySQL removed. 14 [OK]\nraulr\/nginx-wordpress Nginx front-end for the official wordpress:f\u2026 11 [OK]\n1and1internet\/ubuntu-16-nginx-php-5.6-wordpress-4 ubuntu-16-nginx-php-5.6-wordpress-4 6 [OK]\ndalareo\/wordpress-ldap WordPress images with LDAP support automatic\u2026 6 [OK]\nwithinboredom\/scalable-wordpress An easy to scale WordPress 5 [OK]\n1and1internet\/ubuntu-16-nginx-php-7.1-wordpress-4 ubuntu-16-nginx-php-7.1-wordpress-4 3 [OK]\njulianxhokaxhiu\/docker-awesome-wordpress A Docker that combines all the most awesome \u2026 2 [OK]\nwodby\/wordpress-nginx Nginx for WordPress 2 [OK]\ngwee\/wordpress-sendmail-docker wordpress with sendmail 2 [OK]\nwodby\/wordpress-php PHP for WordPress 2 [OK]\ndsteinkopf\/wordpress wordpress clone plus some php extensions 1 [OK]\njulianxhokaxhiu\/docker-wordpress-ldaps WordPress Docker image with LDAPS support 1 [OK]\narm64v8\/wordpress The WordPress rich content management system\u2026 1 \nbakudankun\/wordpress-ja WordPress Japanese Edition forked from offic\u2026 1 [OK]\nowncloud\/wordpress WordPress image for ownCloud websites 1 \napsl\/wordpress WordPress on LAMP managed with circus. Wordp\u2026 1 [OK]\ndavask\/d-wordpress Dockerfile for wordpress 0 [OK]\nitherz\/wordpress WordPress 0 [OK]\nerikzenker\/wordpress wordpress docker image 0 \nansibleplaybookbundle\/wordpress-ha-apb An APB which deploys WordPress HA 0 [OK]\nmattti\/wordpress WordPress adjusted to my own needs 0 [OK]\n<\/code><\/pre>\nOK<\/strong> in the OFFICIAL<\/strong> column indicates that the image is created and supported by the company behind the software<\/small><\/p><\/blockquote>\nDownloading (Pulling) Docker Images<\/h3>\n
If you decide what image you want to use, you can download it to your machine by using the pull<\/code> subcommand.<\/p>\nFor example, we’ll download the official WordPress<\/strong> image. To do this run:<\/p>\n$ sudo docker pull wordpress<\/code><\/pre>\nAfter it finishes downloading the image, the output will look something like this:<\/p>\n
$ sudo docker pull centos\nUsing default tag: latest\nlatest: Pulling from library\/centos\naeb7866da422: Pull complete \nDigest: sha256:67dad89757a55bfdfabec8abd0e22f8c7c12a1856514726470228063ed86593b\nStatus: Downloaded newer image for centos:latest<\/code><\/pre>\nAfter the image is downloaded, you can run a container using it using the run<\/code> command, as we’ve done in the hello-world<\/code> example. If the image has not yet been downloaded, Docker will attempt to pull it from Docker Hub, and then run a container using it.<\/p>\nListing Docker Images<\/h3>\n
To list all of our downloaded images just run:<\/p>\n
$ sudo docker images<\/code><\/pre>\nExample output<\/small>
\n\n
sudo docker images<\/div>
REPOSITORY TAG IMAGE ID CREATED SIZE<\/div>
centos latest 75835a67d134 6 weeks ago 200MB<\/div>
hello-world latest 4ab4c602aa5e 2 months ago 1.84kB<\/div> <\/div><\/p>\n
Further in this tutorial, we’ll see how downloaded images can be modified and generated into new images, which we can then upload to Docker Hub or other Docker registries.<\/p>\n
Step 5 \u2014 Intro to Docker Containers<\/h2>\n
Earlier we played around with the hello-world<\/code> container. We downloaded the image and used it to run the hello-world<\/code> container which just displayed a message and exited after showing us the message. That was just a basic example. Docker containers can do more than that, and we can use them interactively, just like we would with a VPS, but much more resource friendly.<\/p>\nLet’s see an example of how a container can be similar to a VPS. Given the fact that we’re using Ubuntu, let’s go a little crazy and run a container using the latest image of CentOS<\/strong>. Don’t worry if you’ve never used CentOS – what we’re doing is similar to what we’d do on Ubuntu.<\/p>\nWe’ll use the combination of the -i<\/code> and -t<\/code> switches to get interactive shell access to the container:<\/p>\n$ sudo docker run -it centos<\/code><\/pre>\nDocker will most likely not find the image on your machine and pull it from Docker Hub. After it’s downloaded and the container is run, your command prompt will change, reflecting the fact that you’re working inside the container:<\/p>\n
[root@35e04744a977 \/]#<\/code><\/pre>\nThe seemingly random sequence of letters and numbers, 35e04744a977<\/code>, represents the container ID. We use that to identify the container and need it should we want to remove the container.<\/p>\nNow let’s run some basic commands, like update the package database inside the container. On CentOS, to do this, we use yum<\/code> instead of apt<\/code>. You also don’t need to use sudo<\/code>, as you’re now acting as root<\/code> in this container.<\/p>\n# yum update<\/code><\/pre>\nNow let’s install an application on it, such as PHP<\/code>:<\/p>\n# yum install php<\/code><\/pre>\nWhen the installation, if I check the version, I get the following output:<\/p>\n
\n
php -v<\/div>
PHP 5.4.16 (cli) (built: Apr 12 2018 19:02:01)<\/div>
Copyright (c) 1997-2013 The PHP Group<\/div>
Zend Engine v2.4.0, Copyright (c) 1998-2013 Zend Technologies<\/div> <\/div>\n
Any changes you make in the container only apply to that container.<\/p>\n
To exit the container just run exit<\/code>.<\/p>\nList Docker Containers<\/h3>\n
After you’ve used Docker for a while, you’ll most likely be managing a few Docker containers, active<\/strong> and inactive<\/strong>.<\/p>\nTo view your active containers<\/strong> run the following:<\/p>\n$ sudo docker ps<\/code><\/pre>\nSince we’ve got our demo containers inactive, we’ll get the following output:<\/p>\n
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES<\/code><\/pre>\nSo far we’ve run two containers. One from the hello-world<\/code> image, and the other from the centos<\/code> image, but now they’re both stopped.<\/p>\nTo view all of the containers, active<\/strong> and inactive<\/strong>, run the following:<\/p>\n$ sudo docker ps -a<\/code><\/pre>\nThis is the output I’m seeing:<\/p>\n
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES\n35e04744a977 centos \"\/bin\/bash\" 6 hours ago Exited (137) 3 hours ago pensive_northcutt\n82d53d646a6c hello-world \"\/hello\" 19 hours ago Exited (0) 19 hours ago frosty_allen<\/code><\/pre>\nTo view the latest created container, run the following:<\/p>\n
docker ps -l<\/code><\/pre>\nOutput<\/small><\/p>\nCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES\n35e04744a977 centos \"\/bin\/bash\" 6 hours ago Exited (137) 3 hours ago pensive_northcutt<\/code><\/pre>\nStart\/Stop Docker Containers<\/h3>\n
To start<\/strong> a stopped container use docker start<\/code>, followed by the container’s ID (35e04744a977<\/code>) or name (pensive_northcutt<\/code>). In our example I’ll start by using its’ name:<\/p>\n$ sudo docker start pensive_northcutt<\/code><\/pre>\nNow let’s see if it started by listing our active<\/strong> containers:<\/p>\n$ sudo docker ps<\/code><\/pre>\nOutput<\/small><\/p>\nCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES\n35e04744a977 centos \"\/bin\/bash\" 9 hours ago Up 33 seconds pensive_northcutt<\/code><\/pre>\nTo stop the running container, you run docker stop<\/code> followed by the container name or ID:<\/p>\n$ sudo docker stop pensive_northcutt<\/code><\/pre>\nUseful Basic Docker Commands<\/h3>\n
Running commands inside an active<\/strong><\/p>\nWhen you use docker start<\/code> you’ll notice that it’s started, but you’re not interacting with it, such as when you first ran it. To run commands inside it, you can use docker exec -it<\/code>, followed by the ID or name of the container, and followed by \/bin\/bash<\/code>. You’ll notice your prompt change, letting you know that you’ve opened up a new terminal in it:<\/p>\n\n
sudo docker exec -it pensive_northcutt \/bin\/bash<\/div>
[root@35e04744a977 \/]#<\/div> <\/div>\n
The -t<\/code> switch opens a terminal, the -i<\/code> switch makes it interactive, and the \/bin\/bash<\/code> option opens a bash shell to the running container.<\/p>\nExit a container without stopping it<\/strong><\/p>\nYou may find yourself needing to exit the container but wanting it to remain active. To do this, you can type Ctrl+P<\/code> followed by Ctrl+Q<\/code>. You’ll see something like the following output:<\/p>\n[root@35e04744a977 \/]# read escape sequence<\/code><\/pre>\nRenaming a container<\/strong><\/p>\nTo rename a container, you can use docker rename<\/code>, followed by the current name or ID of the container, and then the desired name.<\/p>\nFor example, to better organize my containers, I may want to rename my container named pensive_northcutt<\/code> to a name similar to the naming convention that Docker seems to use, so I’ll call it mr_tiny_nipples<\/code>.<\/p>\n$ sudo docker rename pensive_northcutt mr_tiny_nipples<\/code><\/pre>\nIf I run sudo docker ps<\/code> (because my container is still active), I get the output:<\/p>\n