A Technical I.T./DevOps Blog
Problem scenario
You want to install and configure Apache Camel from source on any distribution of Linux. What do you do?
Solution
You cannot. But there is a way to use Apache Camel as a test.
Background: It is not something that is can be purely installed-and-configured like other applications. Camel is a framework for integrating messaging solutions or microservice architecture.
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Continue reading “How Do You Install and Configure Apache Camel on a Linux Server?”
Problem scenario
You have installed sqlite3. It is a version above 3.22.0. But when you run “make deps” you see this error message:
checking for SQLITE… no
configure: error: Package requirements (sqlite3 = 3.22.0) were not met:
No package ‘sqlite3’ found
What should you do?
Solution
Run this:
sudo apt -y install libsqlite3-dev
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Problem scenario
You have run start-dfs.sh and start-yarn.sh. You have stopped all the Hadoop services too. When you run “jps”, the NameNode is not showing up. You have tried a variety of different troubleshooting methods (including rebooting the NameNode). The NameNode has never worked correctly. You can delete all the data in the cluster because it never really worked. What should you do?
Solution
Run this but remember it will delete all your data:
hdfs namenode -format # Warning: this command will delete all your data in Hadoop …
Continue reading “How Do You Get the NameNode Process to Start in Hadoop?”
Problem scenario
You have added a partition to Linux. When you type “df -h” you do not see evidence that it is available. You tried the “sudo lsblk” command, but you do not see the device. The “fdisk -l” command does show the new device and the size that is available. The command ll /dev/sd* does not show your new device.
When you run “fdisk /dev/sdaX”, you get this: “fdisk: cannot open /dev/sdaX: No such file or directory”
How do you make it available?
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Problem scenario
You are aware that arrays are a supported data type in Bash. You would like to iterate through some variables as arrays could enable complex logic. What do you do?
Solution
The array is zero-based. So the first element is referred to by index number 0.
continualarray=(dog cat hamster rabbit horse cow)
echo ${continualarray[2]}
echo ${continualarray[5]}
Create a file foobar.txt to test an array’s line-reading capacity.
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Problem scenario
You want to use Windows 2016 with 2 GB of RAM. You have Oracle VirtualBox installed on a Linux server. You want the VM to be able to communicate with the host or other VMs on the host. You have a license for Windows 2016. What should you do?
Solution
Prerequisite: You have Oracle VirtualBox set up. You know what adapters you can attach a VM to.
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Continue reading “How Do You Create a Windows 2016 Server with Vagrant and Oracle VirtualBox?”
Problem scenario
You want to return only the JSON of the output that is related to a specific role — not the entire list of an “aws iam list-roles” command. What do you do?
Solution
Prerequisite
You must have the AWS CLI installed. If you need assistance, see this posting.
Procedures
Use the “–query” flag.
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Continue reading “How Do You Filter the Output of an AWS CLI Command?”
Problem scenario
You want to accept user input with a Java program. How do you write such a program?
Solution
Here is the program:
import java.util.Scanner;
public class acceptChar {
public static void main(String[] args) {
System.out.println(“Please enter a character, then press enter: “);
Scanner in = new Scanner(System.in);
char letter = in.next().charAt(0);
System.out.println(letter);
}
}
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Problem scenario
Some processes are a low priority for an OS given their nice level. Why do they eventually run when the OS is active and busy handling processes that have higher priorities? Wouldn’t a nice level that indicates a low priority keep the process starved of receiving resources?
Answer
There is a round robin scheduling algorithm for the CPU to allocate time.
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Problem scenario
You get “ssh connect to host x.x.x.x port 22: Connection refused” when trying to SSH. What do you do?
Possible solution #1
Do you have the correct IP address? Can you copy and paste the IP address? Can you run “ip addr show” on different servers? Is the IP addressed used multiple times in different subnets? It could refer to different servers.
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