A Technical I.T./DevOps Blog
Question
What file controls the configuration setting of the hostname of the server?
Answer
According to Linux+ Complete by Roderick W. Smith (on page 409), most Linux distributions use /etc/hostname.
To make the changes take effect on the server without rebooting, run this command:
sudo hostname –file /etc/hostname
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Continue reading “What File Has Control of the Hostname of the Linux Server?”
Problem scenario
You try to enable a service with this command: sudo systemctl enable foobar
But you get this error: “Failed to execute operation: Invalid argument”
What should you do?
Solution
1. Find the .service file for foobar (e.g., /etc/systemd/system/foobar.service).
2. Find the “Install” section. Is there an extra character? Make sure the line looks right.
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Problem scenario
You try to manually delete EC-2 instances (both worker nodes and the master node of Kubernetes), but this does not work. The EC-2 instances are re-created. How do you delete the cluster?
Solution
Prerequisite
Install and configure the AWS CLI; if you need assistance, see this posting.
Procedures
Run these three commands but substitute “contint.k8s.local” with the name of your cluster:
export KOPS_CLUSTER_NAME=contint.k8s.local
export KOPS_STATE_STORE=s3://$KOPS_CLUSTER_NAME-state
kops delete cluster –name contint.k8s.local –yes …
Continue reading “How Do You Delete a Kubernetes Cluster in AWS?”
Problem scenario
You want to log into the web UI of Foreman. What do you do?
Solution
1. Run this command: sudo find / -name foreman-installer -type f
2. Based on the results above, run this: sudo /path/to/foreman-installer –foreman-version # Replace “path/to” with the results of the first command (e.g., /usr/sbin/”).
3. The output from the above command should show you the credentials for the administrator user.
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Continue reading “How Do You Find The Web UI Credentials for Foreman after You Installed It?”
If you want a great Kubernetes quiz, see this link.
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Problem scenario
You inherited a server with Foreman installed. What should you do to find out what version is installed?
Solution
1. Run this command: sudo find / -name foreman-installer -type f
2. Based on the results above, run this:
sudo /path/to/foreman-installer –foreman-version
# Replace “path/to” with the path results of the first command (e.g., /usr/sbin/”).
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Continue reading “How Do You Know What Version of Foreman Is Installed?”
Problem scenario
You want to write a script that will show which Yum repositories are available to you. You want each one enabled. How do you accomplish this?
Solution
Run this command: sudo yum-config-manager –enable *
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Continue reading “How Do You Enable All Yum Repositories That Are Available?”
Problem scenario
You installed Nginx in a Docker container on a RedHat Linux server. You go to this container with a web browser and see the default screen. Where is the default file (on the back-end) that users see from the front-end by default that says “Welcome to nginx!”?
Solution
This is the name and location of the file (assuming the Docker container was created via the public repository):
/usr/share/nginx/html/index.html
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Continue reading “Where Is The “Welcome to Nginx!” Page Stored in a Docker Container?”
Problem scenario
You want to see options for the yum-config-manager command. How do you find which repositories can be enabled for a Red Hat Enterprise Linux server?
Solution
Run this command: sudo yum repolist all
With the output on the left, you will need what is left of the “/” (forward slash) if one appears in a command like this: sudo yum-config-manager –enable rhui-REGION-rhel-server-rhscl
Let’s say you see this output below from the sudo yum repolist all command:
rhui-REGION-rhel-server-source-supplementary/7Server/x86_64 Red Hat Enterprise Linux Server 7 Supplementary (SRPMs) disabled
To use this output,
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Continue reading “How Do You Determine which yum-config-manager Repos Can be Enabled?”
Problem scenario
You accidentally used a command like this:
sudo rpm -ivh http://path/to…
You accidentally installed and configured a remote repository that you do not want to retrieve packages from. How do you use rpm to remove the configuration?
Solution
1. Run this command: cd /etc/yum.repos.d/
2. Delete the file that is there as a consequence of your “rpm” command.
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Continue reading “How Do You Use rpm to Remove a Repository You Installed?”