{"id":807,"date":"2018-11-29T12:32:27","date_gmt":"2018-11-29T12:32:27","guid":{"rendered":"https:\/\/www.appservgrid.com\/paw93\/?p=807"},"modified":"2018-12-06T23:22:28","modified_gmt":"2018-12-06T23:22:28","slug":"managing-containerized-system-services-with-podman","status":"publish","type":"post","link":"https:\/\/www.appservgrid.com\/paw93\/index.php\/2018\/11\/29\/managing-containerized-system-services-with-podman\/","title":{"rendered":"Managing containerized system services with Podman"},"content":{"rendered":"

\"Managing<\/p>\n

In this article, I discuss containers<\/a>, but look at them from another angle. We usually refer to containers as the best technology for developing new cloud-native applications and orchestrating them with something like Kubernetes<\/a>. Looking back at the origins of containers, we\u2019ve mostly forgotten that containers were born for simplifying application distribution on standalone systems.<\/p>\n

In this article, we\u2019ll talk about the use of containers as the perfect medium for installing applications and services on a Red Hat Enterprise Linux<\/a> (RHEL) system. Using containers doesn\u2019t have to be complicated, I\u2019ll show how to run MariaDB, Apache HTTPD, and WordPress in containers, while managing those containers like any other service, through systemd and systemctl.<\/p>\n

Additionally, we\u2019ll explore Podman, which Red Hat has developed jointly with the Fedora community. If you don\u2019t know what Podman is yet, see my previous article, Intro to Podman (Red Hat Enterprise Linux 7.6)<\/a> and Tom Sweeney\u2019s Containers without daemons: Podman and Buildah available in RHEL 7.6 and RHEL 8 Beta<\/a>.<\/p>\n

Red Hat Container Catalog<\/h2>\n

First of all, let\u2019s explore the containers that are available for Red Hat Enterprise Linux through the Red Hat Container Catalog <\/a>(access.redhat.com\/containers)<\/a>:<\/p>\n

\"\"<\/p>\n

By clicking Explore The Catalog, we\u2019ll have access to the full list of containers categories and products available in Red Hat Container Catalog.<\/p>\n

\"Exploring<\/a><\/p>\n

Clicking Red Hat Enterprise Linux will bring us to the RHEL section, displaying all the available containers images for the system:<\/p>\n

\"Available<\/a><\/p>\n

At the time of writing this article, in the RHEL category there were more than 70 containers images, ready to be installed and used on RHEL 7 systems.<\/p>\n

So let\u2019s choose some container images and try them on a Red Hat Enterprise Linux 7.6 system. For demo purposes, we\u2019ll try to use Apache HTTPD + PHP and the MariaDB database for a WordPress blog.<\/p>\n

Install a containerized service<\/h2>\n

We\u2019ll start by installing our first containerized service for setting up a MariaDB database that we\u2019ll need for hosting the WordPress blog\u2019s data.<\/p>\n

As a prerequisite for installing containerized system services, we need to install the utility named Podman on our Red Hat Enterprise Linux 7 system:<\/p>\n

[root@localhost ~]# subscription-manager repos –enable rhel-7-server-rpms –enable rhel-7-server-extras-rpms
\n[root@localhost ~]# yum install podman<\/p>\n

As explained in my previous article, Podman complements Buildah and Skopeo by offering an experience similar to the Docker command line: allowing users to run standalone (non-orchestrated) containers. And Podman doesn\u2019t require a daemon to run containers and pods, so we can easily say goodbye to big fat daemons.<\/p>\n

By installing Podman, you\u2019ll see that Docker is no longer a required dependency!<\/p>\n

As suggested by the Red Hat Container Catalog\u2019s MariaDB page, we can run the following commands to get the things done (we\u2019ll replace, of course, docker with podman):<\/p>\n

[root@localhost ~]# podman pull registry.access.redhat.com\/rhscl\/mariadb-102-rhel7
\nTrying to pull registry.access.redhat.com\/rhscl\/mariadb-102-rhel7…Getting image source signatures
\nCopying blob sha256:9a1bea865f798d0e4f2359bd39ec69110369e3a1131aba6eb3cbf48707fdf92d
\n72.21 MB \/ 72.21 MB [======================================================] 9s
\nCopying blob sha256:602125c154e3e132db63d8e6479c5c93a64cbfd3a5ced509de73891ff7102643
\n1.21 KB \/ 1.21 KB [========================================================] 0s
\nCopying blob sha256:587a812f9444e67d0ca2750117dbff4c97dd83a07e6c8c0eb33b3b0b7487773f
\n6.47 MB \/ 6.47 MB [========================================================] 0s
\nCopying blob sha256:5756ac03faa5b5fb0ba7cc917cdb2db739922710f885916d32b2964223ce8268
\n58.82 MB \/ 58.82 MB [======================================================] 7s
\nCopying config sha256:346b261383972de6563d4140fb11e81c767e74ac529f4d734b7b35149a83a081
\n6.77 KB \/ 6.77 KB [========================================================] 0s
\nWriting manifest to image destination
\nStoring signatures
\n346b261383972de6563d4140fb11e81c767e74ac529f4d734b7b35149a83a081<\/p>\n

[root@localhost ~]# podman images
\nREPOSITORY TAG IMAGE ID CREATED SIZE
\nregistry.access.redhat.com\/rhscl\/mariadb-102-rhel7 latest 346b26138397 2 weeks ago 449MB<\/p>\n

After that, we can look at the Red Hat Container Catalog page<\/a> for details on the needed variables for starting the MariaDB container image.<\/p>\n

Inspecting the previous page, we can see that under Labels<\/em>, there is a label named usage<\/em> containing an example string for running this container image:<\/p>\n

usage docker run -d -e MYSQL_USER=user -e MYSQL_PASSWORD=pass -e MYSQL_DATABASE=db -p 3306:3306 rhscl\/mariadb-102-rhel7<\/p>\n

After that we need some other information about our container image: the \u201cuser ID running inside the container<\/em>\u201d and the \u201cpersistent volume location to attach<\/em>\u201c:<\/p>\n

[root@localhost ~]# podman inspect registry.access.redhat.com\/rhscl\/mariadb-102-rhel7 | grep User
\n“User”: “27”,
\n[root@localhost ~]# podman inspect registry.access.redhat.com\/rhscl\/mariadb-102-rhel7 | grep -A1 Volume
\n“Volumes”: {
\n“\/var\/lib\/mysql\/data<\/i>“: {}
\n[root@localhost ~]# podman inspect registry.access.redhat.com\/rhscl\/mariadb-102-rhel7 | grep -A1 ExposedPorts
\n“ExposedPorts”: {
\n“3306<\/i>\/tcp”: {}<\/p>\n

At this point, we have to create the directories that will handle the container\u2019s data; remember that containers are ephemeral by default. Then we set also the right permissions:<\/p>\n

[root@localhost ~]# mkdir -p \/opt\/var\/lib\/mysql\/data
\n[root@localhost ~]# chown 27:27 \/opt\/var\/lib\/mysql\/data<\/p>\n

Then we can set up our systemd unit file for handling the database. We\u2019ll use a unit file similar to the one prepared in the previous article:<\/p>\n

[root@localhost ~]# cat \/etc\/systemd\/system\/mariadb-service.service
\n[Unit]
\nDescription=Custom MariaDB Podman Container
\nAfter=network.target<\/p>\n

[Service]
\nType=simple
\nTimeoutStartSec=5m
\nExecStartPre=-\/usr\/bin\/podman rm “mariadb-service”<\/p>\n

ExecStart=\/usr\/bin\/podman run –name mariadb-service -v \/opt\/var\/lib\/mysql\/data:\/var\/lib\/mysql\/data:Z -e MYSQL_USER=wordpress -e MYSQL_PASSWORD=mysecret -e MYSQL_DATABASE=wordpress –net host registry.access.redhat.com\/rhscl\/mariadb-102-rhel7<\/p>\n

ExecReload=-\/usr\/bin\/podman stop “mariadb-service”
\nExecReload=-\/usr\/bin\/podman rm “mariadb-service”
\nExecStop=-\/usr\/bin\/podman stop “mariadb-service”
\nRestart=always
\nRestartSec=30<\/p>\n

[Install]
\nWantedBy=multi-user.target<\/p>\n

Let\u2019s take apart our ExecStart command and analyze how it\u2019s built:<\/p>\n