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Text of the page (random words):
ages in this article we will cover subjects like how to create your own custom image and multi tier applications which runs as a service talking about multi tier we will show you some cool features which you can use when building multi tier apps so let s start and create docker image docker build image there are two ways of creating custom images commit operation inside container itself and dockerfile first option is not recommended because you rely on parent image and already prebuilt container in other words you run the container did some changes and run the commit command it is not so happy solution if you want clean image which was built from beginning dockerfile create docker image with dockerfile is preferred option when you want to build your own images focus is on quality parent image maintainability is then very easy especially if parent image is kept clean by its author motivation of building custom images include adding runtime libraries and ssl certifications changing the dockerfile can trigger updates like removal of unwanted libraries it is not possible to use inline comments and keywords are not word sensitive base or parent image parent image is prepacked image which is source on which other layers are built for example rhel or centos have their base images which are used in first line of dockerfile with word from comment from centos8 8 1 base image has no parent image in from but uses minimal image that is required to build container it uses from scratch directive comment from scratch scratch base image can be found on public docker repository docker hub steps to follow create working directory create dockerfile specs docker build image with docker command dockerfile format comment instruction arguments example apache web server running on centos this is a comment 1 from centos latest 2 label decription apache server 3 run yum install y httpd yum clean all systemctl enable httpd service 4 copy index html var www html 5 expose 80 6 env apacheversion 1 7 entrypoint usr sbin httpd 8 cmd d foreground 9 this is comment parent container to build you custom image is latest version of centos this is just metadata describing image run command executes command in bin sh shell adding extra layer above first layer of parent image notice that there are three commands separated by semicolon in this way you will avoid creating two additional layers with run command this is recommended way of creating custom images and avoiding extra layers and performance issues copy command copies local file which is located on host to new image expose command exposes apache server port 80 to host port 80 for service to be visible to external world set environment variable apacheversion entrypoint defines which command will be executed by default when container starts by default command bin sh c you want httpd command to start immediately cmd provides arguments for the entrypoint instruction steps create working directory dockerfile under your home path inside directory create dockerfile with content above inside same directory create another file index html with following content index html doctype html html head title welcome to apache server title head body p hi i am apache server p body html dockerfile from centos latest 2 label decription apache server 3 run yum install y httpd yum clean all systemctl enable httpd service 4 copy index html var www html 5 expose 80 6 env apacheversion 1 7 entrypoint usr sbin httpd 8 cmd d foreground 9 run the docker build command parameter f indicated which file to use parameter t will name the image because you can t name image inside dockerfile dot tells docker to search for file inside current directory root swmanager dockerfiles docker build f dockerfile t apacheserver sending build context to docker daemon 3 072kb step 1 8 from centos latest removing intermediate container 094156371bd1 f4db33717fe8 step 4 8 copy index html var www html 29536db0b52b step 5 8 expose 80 running in cea0bbe2bb13 removing intermediate container cea0bbe2bb13 b52bb72e819d step 6 8 env apacheversion 1 running in 3b2353124159 removing intermediate container 3b2353124159 a5579f1922d7 step 7 8 entrypoint usr sbin httpd running in 686bc014a689 removing intermediate container 686bc014a689 c0f10b14cb95 step 8 8 cmd d foreground running in ee59e916572f removing intermediate container ee59e916572f dd803595bc27 if you have latest centos image locally docker will use it otherwise it will try to fetch it from docker hub site check that both images are now on your local system root swmanager dockerfiles docker images repository tag image id created size apacheserver latest dd803595bc27 17 seconds ago 237mb centos latest 831691599b88 5 weeks ago 215mb run the apache server container from image root swmanager dockerfiles docker run dit p 80 80 apacheserver fb098d560c26fb97b74268b4e96969c611a4002940f38e6896930ff42397137b check that container is running root swmanager dockerfiles docker ps container id image command created status ports names b921ced4b400 apacheserver usr sbin httpd d 3 seconds ago up 1 second 0 0 0 0 8080 80 tcp ecstatic_chaplygin browse the home page it should display message from custom index html above root swmanager dockerfiles curl 127 0 0 1 8080 doctype html html head title welcome to apache server title head body p hi i am apache server p body html multi container applications in multi container world you can merge two or more containers into the one stack imagine classic three layer stack with front end business and database layer you would normally start these services individually configuring their endpoints and establishing communication between layers here you can define which type of containers will be part of multi container world network storage ports environment variables and many more you build multi tier with docker compose but you can always start containers individually with docker run but this is more convenient way because you have dynamic file where you put all configuration due its dynamic nature multi containers bring challenge in the form of ip addressing each time container is stopped and started there is no guarantee that it will get the same ip address that s way it is important to establish dns services remember the network part where containers which use default bridge network do not have dns services only containers with custom user network use built in dns server docker compose by default will always create custom network docker compose compose is a tool for defining and running multi container docker applications compose is software as well as yaml file to configure your application layers dockerfile can be used in production staging development testing as well as ci workflows to build multi tier container you need 1 dockerfile 2 docker compose file 3 docker compose up command to start building version 3 services app ports 80 80 db image mysql ports 3306 3306 networking building services with docker compose install default network if not specified default network is built from scratch and includes project name directory where docker compose file is located underscore and word default projectname_default in this way all containers are reachable on that network by hostname defined in file there is no firewall between them you can always use pre existing network docker environment variables docker environment variables is just one of the options you can put in docker compose file there are various way to set variables but two main options are direct assignment or assignment by file direct assignment web environment debug 1 assignment by file web env_file web variables env assignment during docker run docker compose run e debug 1 web python console py multiple compose files if you use different environments and workloads you can use multiple compose files by default docker compose runs two files docker compose yml and docker compose override yml first one contains base configuration and second one includes specific configured based on environment by convention the docker compose yml contains your base configuration f option to specify the list of files extending services if your environment has more services that have common set of configuration data you can use feature which is named extending services you can set options in one place and use it anywhere your shared configuration is some kind of template example web extends file common yml service app common yml app build ports 5000 5000 volumes var lib data this instructs web service to use all configuration defined by common yml file example in the following example you will learn how to deploy multi tier application which consists of two images automation_db simple web application coded in python to add delete update data mysql 5 7 mysql database which holds records about data image automation_db was created with following dockerfile from python alpine3 7 copy app workdir app run pip install r requirements txt expose 5000 entrypoint python cmd app __init__ py docker file builds custom image from parent image python alpine3 7 copies app directory with source code and set app as working directory after it installs all requirements which are defined in requirements txt file exposes port 5000 to outside and defines app __init__ py as starting point when run image docker compose file created service and merged two container together version 2 services app image automation latest links db ports 5000 5000 db image mysql 5 7 ports 3306 3306 environment mysql_root_password password mysql_database automation_db volumes mnt mysql mysql57 var lib mysql file consists of two containers app and db app container uses previously build image which we called automation it links to db container and exposes port 5000 to outside second container db uses clean mysql 5 7 image and exposes port 3306 to outside there are two environment variables which are set to successfully start mysql mysql_root_password password defines root password mysql_database automation_db defines pre defined database last entry defines volume path where mysql container reads data path already has automation_db database created two things to consider what about network when you don t specify network in docker compose file docker compose will create custom network for example if docker compose yml file is in home john directory custom network john_default will be created both containers will join this network and each container can now look up the hostname web or db and get back the appropriate container s ip address there is no firewall between containers link keyword in docker compose file link keyword has two functions dependency and extra alias by which service is reachable in our example for app to start successfully it is mandatory to have running database in this case first database is up and then app is connecting to database it is worth to mention that compose does not wait till container is ready only running for mysql full availability you have to define extra logic second function is extra alias which is just one way for services to reach itself by names proof of concept 1 download two containers to your local system automation and mysql data files 2 upload two files to your test linux machine with docker installed 3 download the mysql 5 7 container to your local repository docker pull mysql 5 7 4 unzip mysql data to mnt mysql directory root swmanager tmp mkdir mnt mysql root swmanager tmp unzip mysql57 zip d mnt mysql archive mysql57 zip creating mnt mysql mysql57 extracting mnt mysql mysql57 auto cnf creating mnt mysql mysql57 automation_db inflating mnt mysql mysql57 automation_db db opt inflating mnt mysql mysql57 automation_db esxi frm inflating mnt mysql mysql57 automation_db esxi ibd inflating mnt mysql mysql57 ca key pem inflating mnt mysql mysql57 ca pem inflating mnt mysql mysql57 client cert pem inflating mnt mysql mysql57 client key pem inflating mnt mysql mysql57 ibdata1 inflating mnt mysql mysql57 ib_buffer_pool inflating mnt mysql mysql57 ib_logfile0 inflating mnt mysql mysql57 ib_logfile1 creating mnt mysql mysql57 mysql data will be stored in following path mnt mysql mysql57 5 load the automation_db image root swmanager tmp docker load i automation tar 629164d914fc loading layer 4 464mb 4 464mb 50f8b07e9421 loading layer 838 7kb 838 7kb 9b77965e1d3f loading layer 73 31mb 73 31mb 88e61e328a3c loading layer 4 608kb 4 608kb 5fa31f02caa8 loading layer 6 453mb 6 453mb f5b2455b79ed loading layer 96 77kb 96 77kb c5a6e8eabb7a loading layer 28 24mb 28 24mb loaded image automation latest 6 load the mysql container root swmanager tmp docker load i mysql tar 95ef25a32043 loading layer 72 49mb 72 49mb 492e36400248 loading layer 338 4kb 338 4kb b279ae737dff loading layer 9 539mb 9 539mb 10263d924b2a loading layer 4 2mb 4 2mb ec9e20671283 loading layer 1 536kb 1 536kb 7dbd11e8dc05 loading layer 53 75mb 53 75mb 4fb0c46aefac loading layer 6 656kb 6 656kb 49368a7f4157 loading layer 3 584kb 3 584kb fb6af29036b4 loading layer 313 4mb 313 4mb f803b994f6aa loading layer 16 38kb 16 38kb a52072ac0f07 loading layer 1 536kb 1 536kb 7 check that images are stored on your local system repository tag image id created size automation latest a24edd32a29c 36 minutes ago 108mb mysql 5 7 8679ced16d20 7 days ago 448mb 8 install docker compose root swmanager curl l https github com docker compose releases download 1 26 2 docker compose uname s uname m o usr local bin docker compose total received xferd average speed time time current dload upload total spent left speed 100 638 100 638 0 0 2133 0 2133 100 11 6m 100 11 6m 0 0 570k 0 0 00 20 0 00 20 700k add permissions root swmanager chmod x usr local bin docker compose 9 start docker compose in directory where docker compose file is root swmanager docker compose up creating network root_default with the default driver creating root_db_1 done creating root_app_1 done attaching to root_db_1 root_app_1 db_1 2020 08 04 19 52 50 00 00 note entrypoint entrypoint script for mysql server 5 7 31 1debian10 started db_1 2020 08 04 19 52 51 00 00 note entrypoint switching to dedicated user mysql db_1 2020 08 04 19 52 51 00 00 note entrypoint entrypoint script for mysql server 5 7 31 1debian10 started db_1 2020 08 04 19 52 51 00 00 note entrypoint initializing database files db_1 2020 08 04t19 52 51 355285z 0 warning timestamp with implicit default value is deprecated please use explicit_defaults_for_timestamp server option see documentation for more details db_1 2020 08 04t19 52 52 116427z 0 warning innodb new log files created lsn 45790 db_1 2020 08 04t19 52 52 311565z 0 warning innodb creating foreign key constraint system tables db_1 2020 08 04t19 52 52 461787z 0 warning no existing uuid has been found so we assume that this is the first time that this server has been started generating a new uuid 1504b770 d68c 11ea 91b3 0242ac130002 db_1 2020 08 04t19 52 52 479514z 0 warning gtid table is not ready to be used table mysql gtid_executed can...