Two New Power User Hacks

Tip #1. I learned two new hacks.  – one to regain control and inspect an SSH Session.  Thanks to ServerFault. https://serverfault.com/questions/283129/why-do-consoles-sometimes-hang-forever-when-ssh-connection-breaks ~. – terminate connection (and any multiplexed sessions) ~B – send a BREAK to the remote system ~C – open a command line ~R – request rekey ~V/v – decrease/increase verbosity (LogLevel) ~^Z – […]

FirewallD

Fast commands for enabling firewalld on RHEL7 and CENTOS7. I had to enable these for a secondary control on a project I am on. Check the Status of the Firewall on Each Machine and confirm firewalld is started. systemctl status firewalld ● firewalld.service – firewalld – dynamic firewall daemon    Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor […]

VirtualBox Additions missing

If you see Kernel Headers not found for target kernel level when installing the VBoxLinuxAdditions.run “Please install them and execute”. This issue was found on centos. You’ll see the commands below: yum install “kernel-devel-uname-r ==$(uname -r)” References https://unix.stackexchange.com/questions/232147/your-kernel-headers-for-kernel-3-10-0-229-el7-x86-64-cannot-be-found

Kerberos and Java

I have worked on a kerberos smoke test for my team. I learned a few tips in the process. The useTicketCache is a preferred use in case the java process dies while the KDC is down. HBase Canary Testing runs on a kerberos enabled cluster using hbase canaryhttp://hbase.apache.org/book.html#trouble.client If you are port forwarding over SSH, […]

Forwarding DGram in node.js

For a project I am working on I needed to rewrite a DGram port. I moved the ports around and found a few quick tests. Testing with NC my-machine:~$ echo -n “data-message” | nc -v -4u -w1 localhost 88found 0 associationsfound 1 connections:1: flags=82<CONNECTED,PREFERRED> outif (null) src 127.0.0.1 port 53862 dst 127.0.0.1 port 88 rank […]

COS and Hadoop FS issue

I ran into this issue with Python and IBM Cloud Object Storage. I applied a quick fix: pyspark –packages com.ibm.stocator:stocator:1.0.24 https://github.com/ibm-watson-data-lab/ibmos2spark/tree/master/python https://github.com/ibm-watson-data-lab/ibmos2spark/tree/master/pythonhttps://blog.sicara.com/get-started-pyspark-jupyter-guide-tutorial-ae2fe84f594f https://stackoverflow.com/questions/46011671/no-filesystem-for-scheme-cos

Kafka, Zookeeper… and Kerberos

My team runs a Kafka service for data ingestion, we ran across a rare timeout when our main Key Distribution Center (KDC) went down. When the zookeeper service restarted, zookeeper worked flawlessly. I checked the services with the zookeeper four-letter commands. However, the kafka-broker/zookeeper startup and authentication failed and the brokers went down. We checked […]

Tracking down RPM install dates/reasons/who

I had to find the date of an RPM install to track the lineage of an RPM. I found two very helpful commands. The “rpm -q basesystem –qf ‘%{installtime:date}\n’”, which I found thanks to StackExchange, was exceptionally helpful for placing the date/time of an installed RPM. The rpm -qi basesystem also provided some excellent additional […]