How Do You Troubleshoot Maven Giving You an Error Such as “java.lang.OutOfMemoryError java heap space”?

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Problem scenario
You are getting an error such as “java.lang.OutOfMemoryError java heap space”

You have plenty of swap space available, but this error persists. The problem is as if nothing is using swap space you know exists. Why won’t your Java program or Maven build utilize the swap space that is available to it?

Possible solution #1 (for Maven builds)
Run a command like one of these (but uncomment the second one if you want to commit roughly 5 GB of memory to the maven build):

export MAVEN_OPTS=-Xmx512m
# export MAVEN_OPTS=-Xmx5120m

Now retry your mvn command.

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How Do You Handle a Discrepancy between NMAP Results?

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Problem scenario
From two different servers the nmap results show different ports are open. What is the likely cause of this problem?

Possible Solution #1
Is there a firewall between the two servers? Some firewalls block incoming or outgoing connections exclusively. An OS level firewall or other intermediate firewall could easily produce discrepant nmap results based on the servers running the nmap command.

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How Do You Install SUSE when You Encounter “The System cannot be installed because … There is no device mounted at ‘/'”?

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Problem scenario
You are trying to install Linux SUSE. You get an error “The System cannot be installed because the following errors were found: There is no device mounted at ‘/’. How do you get passed this problem?

Solution
Use the “Expert Partitioner”. Verify you have one device (e.g., /dev/sda1) that has the Type “BIOS Boot Partition.” Verify you have one device (e.g.,

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How Do You Connect to a VM in Oracle VirtualBox from a Desktop?

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Problem scenario
You are connecting to a VM in Oracle VirtualBox from a desktop. The pings to the VM are not responding. What should you do?

Solution
Go to Devices -Network -Network Settings
The “Attached to:” setting hould be “Bridged Adapter”
The “Name” setting should what you think is appropriate. Not uncommonly this will be en0 Wi-Fi.
Expand the “Advanced” settings.

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How Do You Install CentOS when the Installation Source Option is a URL Exclusively (without an Option for a Local ISO)?

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Problem scenario
You are trying to install CentOS in an offline manner. You get to the “Installation Summary” screen. The Software section says “Installation Source…Setting up installation source.” There is a yellow triangle with an exclamation point near the “Installation Source” button. The “Begin installation” button is grayed out. You want to choose a local ISO, and you thought it was installing via a local ISO. You do not have access to the internet.

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How Do You Use the Bisect Module in Python?

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Problem scenario
You want to use bisect in Python. How do you do this?

Solution

# This program was adapted from code found
# https://docs.python.org/3/library/bisect.html

import bisect
def grade(score, breakpoints=[60, 70, 80, 90], grades=’FDCBA’):
i = bisect.bisect(breakpoints, score)
return grades[i]

x = [grade(score) for score in [71, 88, 94]]
print(x)

import bisect
def whether(temperature, breakpoints=[38, 70, 80, 100], descriptors=[”cold”, “cool”, “warm”, “hot”, “very hot”]):
i = bisect.bisect(breakpoints, …

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How Do You Configure Email Alerts for AWS Spending Thresholds of Specific Dollar Amounts?

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Problem scenario
Sometimes you forget what is running in AWS. You want to be notified when you have spent a certain amount of money. How do you set up a notification in your AWS account that will apprise you when you have have spent over a certain amount of money for a given month?

Solution

  1. Log into the AWS Management Console (aka the web UI).

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What Do You Do when ImportExportTools is Not an Option in Thunderbird?

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Problem scenario
You installed ImportExportTolls NG, the add-on in Mozilla Thunderbird. In Thunderbird you go to Tools, but “ImportExportTools” or “ImportExportTools NG” is not visible. What do you do?

Solution
You need to have a mailbox — even an empty mailbox — configured. This will import all the messages you are trying to import into that mailbox. The hamburger icon’s Tools -Import,

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