RHCSA 8 EX200 Exam Practice Question 9 (Managing Containers In Linux)

October 2, 2020 Victor RHCSA 8 DUMPS/Exam Practice Questions 19

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RHCSA 8 Exam Practice Question 9

Question

As the student user, create a detached apache http web server container with the name, (site1) and with the tag that has the lowest version(1-112) from rhel8/httpd-24 image. Use the registry.redhat.io registry.

Use the username, administrator and the password, admin123

Create and mount the ~/storage/html/ directory as a persistent storage to the container as /var/www/. The content of ~/storage/html should be extracted from /tmp/image/containers.tgz

Also, Port 8080 on the container should be mapped to port 8080 on the host. Declare the environment variables, HTTPD_USER and HTTPD_PASSWORD and use admin as their values.

configure the container as a service using systemd and make the web server/container persistent across reboot.

The question is based On managing containers In The RHCSA 8 Course on this website. If you have gone through this course, solving this wouldn’t be a problem.

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Managing Containers In Linux

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Answer

1. Before we can configure containers, we need the container-tools module. Verify if the container-tools module is installed.

[student@DRDEV1 ~]# sudo yum module list --installed |grep container-tools

2. Install container-tools module.

[student@DRDEV1 ~]# sudo yum module install container-tools -y

Updating Subscription Management repositories.
Last metadata expiration check: 0:00:30 ago on Mon 30 Nov 2020 05:15:34 PM GMT.
Dependencies resolved.

3. login to the image registry using the credentials given.

NB: see the lesson pertaining to this course to see how I was able to login.

[student@DRDEV1 ~]$ podman login registry.redhat.io
Username: administrator
Password:
Login Succeeded!
[student@DRDEV1 ~]$

4. Inspect the httpd-24 image and search for the lowest tag.

NB: Sometimes, you may be given the tag to use.

[student@DRDEV1 ~]$ skopeo inspect docker://registry.redhat.io/rhel8/httpd-24 |more

{
    "Name": "registry.redhat.io/rhel8/httpd-24",
    "Digest": "sha256:43b6a13d3e6674ec684ba2cdf433633cabe4963a24e00b59f32532b31bbf1ce5",
    "RepoTags": [
        "1-112",
        "1-118",
        "1-118-source",
        "1-70",
        "1-30.1562749848",
        "1-76",
        "1-52",
        "1-42",
        "1-30",
        "1",
        "1-76.1584015406",
        "1-98",
        "1-112.1599745027",
        "1-92",
        "1-104",
        "1-105",
        "1-60",
        "1-63",
        "1-92.1590691900",
        "1-30.1561731107",
        "1-28",
        "1-25",
        "1-89",
        "latest"
RHCSA 8 EX200 exam practice question 9

5. download the container image from the registry.

[student@DRDEV1 ~]$ podman pull registry.redhat.io/rhel8/httpd-24:1-112

Trying to pull registry.redhat.io/rhel8/httpd-24:1-112...
Getting image source signatures
Copying blob da1cc572023a done
Copying blob c4d668e229cd done
Copying blob ec1681b6a383 done
Copying blob f32fb687aa09 done
Copying config e00cffb90b done
Writing manifest to image destination
Storing signatures
e00cffb90b6479531b8c5baa0d0ba57019c811184824246d73628079644b8ca6

Before we create the container, Let’s prepare the persistent storage that will be attached to the container.

6. verify if /home/student/storage/html exists.

[student@DRDEV1 ~]$ ls -l /home/student/storage/html

ls: cannot access '/home/student/storage/html: No such file or directory

7. make the ~/storage/html directory

[student@DRDEV1 ~]$ mkdir -p /home/student/storage/html

8. Extract the content of /tmp/image/containers.tgz to ~/storage/html directory.

[student@DRDEV1 ~]$ tar xfv /tmp/image/containers.tgz -C /home/student/storage/html/

index.html

9. view the content of storage/html directory

[student@DRDEV1 ~]$ cat storage/html/index.html

###################This is a web file for your container images on storage#################

10. verify others have the read permission on the file. Other users should be able to read the file.

so make sure the directory has the read and execute permission and the file has the read permission.

[student@DRDEV1 ~]$ ls -ld storage/

drwxrwxr-x. 3 student student 18 Dec  7 17:19 storage/
[student@DRDEV1 ~]$ ls -ld storage/html/index.html

-rw-rw-r--. 1 student student 92 Dec  7 17:22 storage/html/index.html

11. Now, let’s create the container

[student@DRDEV1 ~]$ podman run -d --name site1 -p 8080:8080 -e HTTPD_USER=admin -e HTTPD_PASSWORD=admin -v /home/student/storage:/var/www:Z registry.redhat.io/rhel8/httpd-24:1-112

20432130c52d9c1cec9eac62f24503da8c0a271a51aba9324548a11194c75550

12. Verify that the container is running.

[student@DRDEV1 ~]$ podman ps

CONTAINER ID  IMAGE                                    COMMAND               CREATED         STATUS             PORTS                   NAMES
20432130c52d  registry.redhat.io/rhel8/httpd-24:1-112  /usr/bin/run-http...  50 seconds ago  Up 50 seconds ago  0.0.0.0:8080->8080/tcp  site1

13. Verify that you can access the storage on the container with the forwarded port.

[student@DRDEV1 ~]$ curl http://localhost:8080

###################This is a web file for your container images on storage#################

Now, we need to configure the container as a systemd service

14. create the systemd directory where a user’s unit files can be defined (~/.config/systemd/user). In this case, the student user.

 [student@DRDEV1 ~]$ mkdir -p /home/student/.config/systemd/user

15. generate student user’s unit file so that we can make use of container as a service

NB: make sure the unit file is generated in (~/.config/systemd/user) directory.

[student@DRDEV1 ~]$ cd /home/student/.config/systemd/user/
[student@DRDEV1 user]$ podman generate systemd --name site1 --files --new

16. Verify that the unit file has been generated

[student@DRDEV1 user]$ ls

container-site1.service

17. make the “container as a service” persistent across reboot

[student@DRDEV1 user]$ loginctl enable-linger

Verify that linger is enabled for the student user

[student@DRDEV1 user]$ loginctl show-user student

UID=1005
GID=1005
Name=student
Timestamp=Mon 2020-12-07 09:19:31 GMT
TimestampMonotonic=245042201
RuntimePath=/run/user/1005
Service=user@1005.service
Slice=user-1005.slice
Display=47
State=active
Sessions=47 4 2
IdleHint=no
IdleSinceHint=0
IdleSinceHintMonotonic=0
Linger=yes

18. so now, let’s start the container as a service

* stop the container first, and remove the archived container

[student@DRDEV1 ~]$ podman stop  site1

28d99a8041ccb30fc9335af638cadb22544fcf13a6319d6086c74d3539040473

[student@DRDEV1 ~]$ podman rm site1

28d99a8041ccb30fc9335af638cadb22544fcf13a6319d6086c74d3539040473

* verify that the container has been stopped and removed

[student@DRDEV1 ~]$ podman ps

CONTAINER ID  IMAGE   COMMAND  CREATED  STATUS  PORTS   NAMES
[student@DRDEV1 ~]$ podman ps -a

CONTAINER ID  IMAGE   COMMAND  CREATED  STATUS  PORTS   NAMES

*start the container as a service

[student@DRDEV1 ~]$ systemctl --user daemon-reload

* enable the container as a service to start across reboot.

[student@DRDEV1 ~]$ systemctl --user enable --now container-site1

Created symlink /home/student/.config/systemd/user/multi-user.target.wants/container-site1.service → /home/student/.config/systemd/user/container-site1.service.
Created symlink /home/student/.config/systemd/user/default.target.wants/container-site1.service → /home/student/.config/systemd/user/container-site1.service.

19. verify that the container has started.

[student@DRDEV1 ~]$ podman ps

CONTAINER ID  IMAGE                                    COMMAND               CREATED             STATUS                 PORTS                   NAMES
20432130c52d  registry.redhat.io/rhel8/httpd-24:1-112  /usr/bin/run-http...  About a minute ago  Up About a minute ago  0.0.0.0:8080->8080/tcp  site1

20. Verify the content of the container storage

[student@DRDEV1 ~]$ curl http://localhost:8080

###################This is a web file for your container images on storage#################

21. stop the container and reboot the system if you wish and verify that the container is persistent.

[root@DRDEV1 ~]# systemctl --user stop container-site1
[root@DRDEV1 ~]# reboot
[student@DRDEV1 ~]$ podman ps

CONTAINER ID  IMAGE                                    COMMAND               CREATED         STATUS             PORTS                   NAMES
20432130c52d  registry.redhat.io/rhel8/httpd-24:1-112  /usr/bin/run-http...  12 minutes ago  Up 12 minutes ago  0.0.0.0:8080->8080/tcp  site1

Solution Summary

sudo yum module list –installed |grep container-tools

sudo yum module install container-tools -y

podman login registry.redhat.io

skopeo inspect docker://registry.redhat.io/rhel8/httpd-24 |more

podman pull registry.redhat.io/rhel8/httpd-24:1-112

ls -l /home/student/storage/html

mkdir -p /home/student/storage/html

tar xfv /tmp/image/containers.tgz -C /home/student/storage/html/

podman run -d –name site1 -p 8080:8080 -e HTTPD_USER=admin -e HTTPD_PASSWORD=admin -v /home/student/storage:/var/www:Z registry.redhat.io/rhel8/httpd-24:1-112

curl http://localhost:8080

mkdir -p /home/student/.config/systemd/user

cd /home/student/.config/systemd/user/

podman generate systemd –name site1 –files –new

loginctl enable-linger

systemctl –user daemon-reload

systemctl –user enable –now container-site1

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19 Comments

  1. Hello Victor\
    thanks for valuable info when i run systemctl status container-ihs1.service, i am getting `unit container-ihs1.service could not be found`
    any idea

    Reply

  2. Hello Victor\
    I changed generated containder-ihs.service content; replaced wants line with `wants=syslog.servic` and it is working, br

    Reply

  3. Thanks a lot. I got your premium Questions and answers and your site has really helped me. I am preparing for my next phase which is RHCE. Do you have any package for RHCE.

    Reply

  4. Victor h ,

    the question states ” Create and mount the ~/storage/html/ directory as a persistent storage to the container as /var/www/…”

    And your answer states ” podman run -d –name site1 -p 8080:8080 -e HTTPD_USER=admin -e HTTPD_PASSWORD=admin -v /home/student/storage:/var/www:Z registry.redhat.io/rhel8/httpd-24:1-112 ”

    Why did you not enter “/home/student/storage/html ” does this do the same…?

    Reply

    • it can be any but i will strongly recommend “/home/student/storage/html” since that was what the question explicitly said. Nice observation though. Good one!!!

      Reply

  6. Why adding a –new, once you stop it and you generate the service file, without the new you wont neet to remove the stopped container. Does it make any difference for the examn, as I read to take care with the new option in production environments.

    Reply

      • actually new comment is not supported in exam environment . when we put new it show an error like new comment not found. if u ignore this command and try to execute podman generate without new then you can not start the service . how can we fix this issue.
        Kindly please address this issue and provide a solution.

        Reply

  7. how will you be able to answer a question like this on the exam if there is no internet connection during the exam? you would need to be able to log on to the registry and pull the image.

    Reply

  8. how would tasks like these be asked as a question on the exam if you don’t have an internet connection during the exam?

    Reply

  9. Hi,
    I have a confusion with the persistent storage part.
    The q says:
    “Create and mount the ~/storage/html/ directory as a persistent storage to the container as /var/www/. The content of ~/storage/html should be extracted from /tmp/image/containers.tgz”

    So from here it stands: /home/student/storage/html:/var/www

    If so, when the container will look for its index.html file, it will look for: “/var/www/html/index.html”

    Now if I mount as per the question (ie. /home/student/storage/html:/var/www)
    then, that /var/www/html/index.html file eventually should be this file (by replacing /var/www by /home/student/storage/html): /home/student/storage/html/html/index.html, NOT /home/student/storage/html/index.html

    So if I want to follow the Q exactly, I have to mount like this /home/student/storage/html:/var/www and I have to have directory/index file in host like this: /home/student/storage/html/html/index.html, with 2 html directory created.

    Is my understanding correct? I have checked it; it does work only the way I explained;

    Thanks and Reg

    Reply

  10. I will also recommend to add this:
    after extracting archive files
    1.) semanage fcontext -a -t container_file_t ‘/storage(/.*)?’
    2.) restorecon -R /storage

    Reply

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