A Technical I.T./DevOps Blog
Problem scenario
You want to bypass Docker and configure the cgroups directly. You want new Docker containers to be governed by these customized settings. What should you do?
Solution
You may not want to bypass Docker for your cgroup modifications. You should read about the libcontainers. By default Docker uses libcontainers for granular configuration changes along the lines of modifying cgroups settings.
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Question
What is a Secret in Kubernetes?
Answer
It is a ConfigMap with sensitive data that is encoded in Base64 text. What is a ConfigMap? It is a .yaml with a special format. There is always a “data:” section that is part of the YAML definition of a ConfigMap. The key-value pairs in the “data” section will have keys that appear in regular text;
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Problem scenario
You have heard of the immutable bit and want to know how it is different from the sticky bit. What is the immutable bit versus the sticky bit? What are the differences between the two?
Solution
We like the term “immutable flag” as opposed to “immutable bit” to help distinguish the two. We have three parts to explain this.
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Continue reading “What Is The Immutable Bit vs. The Sticky Bit?”
Problem scenario
You are used to AWS Security Groups. You created a firewall rule in GCP. You cannot seem to reach the GCP server. What is wrong?
Possible Solution
Does the GCP firewall rule use the same shorthand notation like this?
x.x.x.x/32
Inbound rules in AWS Security Groups use the /32 to allow an IP address to connect to an EC-2 instance or service.
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Continue reading “How Do You Open a Port to Connect to a GCP server?”
Problem scenario
You want to use the same command for encryption and compression. You want the compression to be high (for maximum data density for backups and storage purposes). You can install a new package. What should you do?
Solution
Use 7zip.
Prerequisite
Try whereis 7z to see if 7zip is installed. If it is not,
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Problem scenario
You try to run terraform apply to create an Azure VM but you receive a message like this:
Error: Error applying plan:
1 error(s) occurred:
* azurerm_virtual_machine.myterraformvm: 1 error(s) occurred:
* azurerm_virtual_machine.myterraformvm: compute.VirtualMachinesClient#CreateOrUpdate: Failure sending request: StatusCo” Message=”Authentication using either SSH or by user name and password must be enabled in Linux profile.” Target=”linux”
What should you do?
Solution
1.
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Problem scenario
You have a heterogeneous enterprise network of servers. You want your Linux machines to communicate and transfer files with your Windows machines. You do not want to use Active Directory. What do you do?
Solution
1. Install Cygwin on the Windows server if it has not been set up already. If you need assistance with this, see this posting.
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Continue reading “How Do You Set up SSH on a Windows 2016 Server with Cygwin?”
Problem scenario
You cannot ping a server, but your nmap results show that port 22 on the server is open. You can reach the server with nmap, but not with ping. What is wrong?
Possible solution
Is the server in the AWS Security Group that you think it is? Go to the AWS console and verify the security group for the server is what you think is correct.
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Continue reading “Why Cannot You Ping a Server when Nmap Commands to The Server Work?”
Problem scenario
You want to set up Zookeeper with three nodes in AWS. What do you do?
Solution
1. Install Zookeeper on each of the servers. If you need assistance with this, see this posting.
2. Modify the zoo.cfg file on each of the servers. Add stanzas like these but substitute foobarX.amazonaws.com with the Public DNS name of each server:
server.1=foobar1.amazonaws.com:2888:3888
server.2=foobar2.amazonaws.com:2888:3888
server.3=foobar3.amazonaws.com:2888:3888
initLimit=5
syncLimit=5
3.
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Continue reading “How Do You Set Up a Multi-Node Cluster of Zookeeper?”
Question
What is SELinux?
Answer
Security-Enhanced Linux (or SELinux) is a kernel module that can be installed and turned on in a Linux server. It categorizes files, hardware resources and processes; to learn more see this posting. It has the ability to restrict access to these categories. If a server is designated as an application server, a database server,
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