A Technical I.T./DevOps Blog
Problem scenario
You have a small AWS server (e.g., t2.nano with 0.5 GB of RAM) running Ubuntu. How do you install Nagios on it?
Solution
1. As root or a sudoer user, run a script with the following content (sudo bash /tmp/install.sh):
# Written by continualintegration.com
#This script installs Nagios. There is some interactive portion at the beginning.
# But it should be easy to install Nagios using the following.
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Continue reading “How Do You Install Nagios on Ubuntu Step-By-Step?”
Problem scenario
You have Java installed. The “java -version” command returns data showing that Java was been installed correctly. You try to use the javac command to compile a .java file. You get this error:
-bash: javac: command not found
How do you compile your Java code when javac is not recognized?
Solution
As root,
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Continue reading “How Do You Troubleshoot This Error “javac: command not found”?”
Problem scenario
You want to change the MAC address of your wireless network adapter (e.g., you want a WiFi network to see your laptop as a different or new machine). How do you do this?
Solution
1. Go to Control Panel -Network and Internet
2. Go to “Network and Sharing Center”
3. Click on “Change adapter settings”
4.
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Problem scenario
With a SQL front end (e.g., pgAdmin or HeidiSQL) you get this error “could not connect to server: Connection refused 0x0000274D/10061) Is the server running on host “x.x.x.x” and accepting TCP/IP connections on port 5432?
You double checked you are trying to connect to the correct IP address (x.x.x.x). You know port 5432 is not blocked. You know the postgres service is listening on port 5432 on the destination server.
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Worried about being sued for something you posted online? You may need to educate yourself about the risks.
American citizens may want to understand the context of online defamation by buying Be Careful Who You SLAPP by Delfino and Day. To learn about strategic lawsuits designed to silence people in the USA, there is no better book than SLAPPs: Being Sued for Speaking Out by Rock Pring.
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Continue reading “Comprehending Being Sued for Online Postings (e.g., Frivolous Libel Lawsuits)”
Problem scenario
You want to know where the Linux users are logging on from (e.g., for security and configuration reasons). You want to know the IP addresses of their desktops. Where do you find the IP address from most recent login on a Linux server?
Solution
To see the most recent login session details (including IP address), run this command:
last
After you press enter you’ll see the most recent logins.
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Continue reading “Where Do You Find the IP Address from Most Recent Login on a Linux Server?”
Background
For troubleshooting networking issues with a Linux/Unix server, the nmap utility is extremely useful. For Windows with PowerShell version 3, there is a script can help you almost as much as nmap; see this posting if you are interested. For newer versions of PowerShell, use the Test-NetConnection command.
Problem scenario
You use nmap to test a port on an IP address.
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Continue reading “How Do You Troubleshoot a False “State” Value in nmap Results?”
Problem scenario
From a Linux command prompt (e.g., Linux terminal) you want to connect to a specific Postgres database. How do you create a table or issue SQL commands to a specific Postgres database from the back-end (the Postgres server itself)?
Solution
1. First enter the Postgres command prompt by running these two commands:
sudo -i -u postgres
psql
2.
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Continue reading “How Do You Connect to a Specific Postgres Database without a SQL Front End?”
Problem scenario
You want to install Docker on Linux. How do you determine if the VM or physical server with Linux meets the minimum requirements for installing Docker?
Solution
Run this script:
#!/bin/bash
# Written by continualintegration.com
echo “This will test if your Linux server is ready for Docker.”
i=0;
os=$(uname -m | grep -i x)
if [ -z “$os” ];
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Continue reading “How Do You Know If Your Linux Server Can Support a Docker Installation?”
Problem scenario
You want to install Docker, but you want to be sure that the kernel is high enough to be supported.
Solution
The minimum kernel version is stated on Docker’s website. As the spring time of 2017, run this script to find out if your kernel version is high enough:
a=$(uname -r)
b=$(echo $a | awk -F
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Continue reading “How Do You Know If Your Linux Kernel Meets the Minimum Requirements for Docker?”