Category: Linux

Apache Tomcat 9 – SSL/TLS Configuration HOW-TO

In this exercise, Tomcat 9 will be installed with OpenJDK 8 using a self-signed certificate in a PKS12 keystore on a clean CentOS 7 Linux server using the Http11NioProtocol protocol.  These are the steps. ######################################################################################## # Apache Tomcat 9 ######################################################################################## yum install wget vim net-tools firewalld unzip -y yum install java-1.8.0-openjdk-devel -y cd /opt/app wget http://us.mirrors.quenda.co/apache/tomcat/tomcat-9/v9.0.16/bin/apache-tomcat-9.0.16.tar.gz tar xzvf apache-tomcat-9.0.16.tar.gz ln…

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Install Elastic Stack 5.6 on CentOS 7

By combining the massively popular Elasticsearch, Logstash, and Kibana (what was the ELK Stack is now the Elastic Stack), Elastic has created an end-to-end stack that delivers actionable insights in real time from almost any type of structured and unstructured data source. There are many resources that offer installation procedures from simple to complex configurations. This is my take on…

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Migrate User Accounts from one CentOS server to another CentOS server

There are many articles that suggest that simply copying certain files from one CentOS to another CentOS server will be sufficient enough to migrate the user accounts along with their permissions and passwords.  Other arguments suggest that certain files such as the passwd and shadow files should never be manually edited; but the caveat is that there is no “utility”…

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Automate the kinit process with a secure password

If in the event you want to automate the kinit process and automate this process at logon, the steps outlined below will work.  This has been tested on a CentOS 7 installation. ktutil ktutil: addent -password -p username@DOMAIN.COM -k 1 -e rc4-hmac Password for username@DOMAIN.COM: [enter your password] ktutil: addent -password -p username@DOMAIN.COM -k 1 -e aes256-cts Password for username@DOMAIN.COM:…

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Atlassian JIRA support for unsupported OpenJDK

Atlassian JIRA does not support OpenJDK. Oracle has changed it licensing for Oracle JDK.  With that in mind, the goal is to use OpenJDK as a replacement for the Oracle JDK. This is possible and easy to do. Search for your jira install %JIRA_HOME/jira/bin/check-java.sh.  On the line that contains “java version” change it to “openjdk version“, then restart your install…

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pihole becomes unresponsive

If pihole becomes unresponsive, one reason may be that the diskspace is full. The diskspace may become full from an excessively large pihole database and or /var/log entries.  In a recent case, both were the cause.  Stopping the services and truncating the logs in /var/log and deleting the database worked in this case.  The following logs were large, but I…

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pihole reset all stats

There may be a time where you want to have a fresh dashboard without the stats and logs.  A case maybe a misconfigured NIC that may dump millions of DNS queries into the logs.  Yup I have seen this happen. Whenever you need to reset the pihole stats and logs that display on the /admin dashboard, the following options will…

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Create systemd services for Atlassian Apps

While working with the Atlassian products over the years, a pattern emerges. Even though there are distinct differences in their setup and configurations, the installation process can be generalized. One of the post-installation considerations to make is in the manual creation of a service.  The benefit of a service is that it will automate the running of the application, rather…

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CentOS 7 df command hangs

The df command is useful in reporting disk space usage.  However, recently encountered a system that would hang after issuing the df command.  A CTL-C or CTL-Z would not escape this annoyance.  The issue was quickly resolved by reinstalling stystemd. yum -y reinstall systemd After reinstalling systemd, the df command was reissued and was quite responsive. Source https://serverfault.com/questions/911811/centos-7-df-started-to-hang

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The cd command in CentOS 7

I have been working in a CLI environment for many years, so the cd “change directory” command is nothing new to me; however, an accidental typo presented an unexpected result.  Instead of typing “cd ..” which would transverse back one directory, a user typed only “cd” with the intention of pasting from the clipboard the rest of the path.  The…

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VIM: Preserve File Date with Touch

I had a single file I needed to modify but didn’t want to modify the date of the file.  It was a minor change to the file, so I wanted to maintain the file date for posterity.  In any case, I learned the vim does not provide this functionality, but touch would and quite easily.  With that said, I am…

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Determine which processes are using swap in Linux

Some servers may have several applications, each running in their own allocated piece of RAM and SWAP.  It seems easy enough to use `top` to determine memory usage, but it wasn’t so obvious (to me) as to how to determine swap usage.  A nifty little command called smem to the rescue. So what is smem?  It is a “Report memory…

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ssh logins using keys

I have wanted to experiment and expand upon different ways of ssh’ing into one linux box from another using the ssh-keygen.  This article demonstrates several different methods that I have tested and used throughout the years. Actually what has happened, is that over time, scripting evolved and always seem to make tweaks along the way. yum install -y sshpass echo…

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Spacewalk Certificate expiration warning [Resolved] 2018

I’m not going to go into detail as to what spacewalk is and what this message is all about, you are here for a reason.  You may have received an auto-generated email from Spacewalk to “inform you that your Spacewalk Certificate has expired on your [fqdn] server. After 4 day(s) the systems management services provided by your Spacewalk Server will…

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How to change user name in CentOS

A username needed to be changed on a local install of a CentOS Linux box.  Here are the steps taken to resolve the issue. usermod -l new old mv /home/old/ /home/new/ groupmod -n new old chown new:new /home/new/ chown new:new /home/new/ -R passwd new

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How to add desktop icons on CentOS 7

For the most part, I prefer to work using the terminal on a minimal install of Linux; however, there are those occasional times where the GUI is necessary.  Recently faced with having to add a few desktop shortcuts to the Desktop posed a bit of a problem for me. Basically, wanted to achieve two things, a Desktop icon to launch…

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VIM: Join Lines

I had a document where I wanted to join every other line.  I tried several approaches on a Windows box using Cygwin but only one worked with a couple variations.  Using the vim editor.  This is a new trick to me, and wanted to jot it down before I forget about. The file looked something like this. 10.10.10.10 a.com 10.10.10.11…

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