Author Archives: ronaldpringadi

CentOS 6 repo Settings

Posted on March 2, 2018 by ronaldpringadi

To fix repo settings in CentOS 6 1. make sure there is no proxy or funny settings in vi /etc/yum.conf 2. There are a couple of files within /etc/yum.repos.d/. Make sure the url are correct (accessible) and enabled=1 ll /etc/yum.repos.d/ … Continue reading →

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Show Linux Partition Tree Mountpoint and If SSD

Posted on June 27, 2017 by ronaldpringadi

1lsblk -o TYPE,NAME,KNAME,UUID,MOUNTPOINT,SIZE,ROTA

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Setting log4j log level programmatically

Posted on June 8, 2017 by ronaldpringadi

Sometimes you don’t want to ship a log4j.properties file — you want to spin up logging in code. Useful inside unit tests, one-off debug runs, or anywhere you want to flip log levels at runtime. Here’s a self-contained setupLog4j() that … Continue reading →

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Print java stack trace from anywhere

Posted on May 26, 2017 by ronaldpringadi

Need to know which code calls a specific location? Dump the stack trace: 1234import org.apache.commons.lang3.exception.ExceptionUtils; // …somewhere in your method: LOG.trace(ExceptionUtils.getStackTrace(new Throwable())); You’re constructing a Throwable just to capture the current stack — you’re not throwing it. ExceptionUtils.getStackTrace turns the … Continue reading →

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Knowing your exception class name

Posted on May 25, 2017 by ronaldpringadi

You’re staring at a generic catch (Exception e) and you don’t know which actual exception is being thrown. The trick is to log the runtime class so you can replace the generic catch with a specific one: 12345} catch (Exception … Continue reading →

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SELinux directory permission

Posted on November 8, 2016 by ronaldpringadi

To check SELinux directory permission you need to -z for example 1ls -Z /var/www/html If something is incorrect you can re-adjust some of the directory permission: 1chcon -R -t httpd_sys_content_t /var/www/html

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RedHat / Centos Firewall

Posted on November 8, 2016 by ronaldpringadi

To add an exception to firewall In RedHat/CentOS 6 12345iptables –line -vnL iptables -A INPUT -p tcp –dport 80 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -p tcp -s 192.168.0.0/16 -j ACCEPT iptables -D INPUT -p tcp -s … Continue reading →

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Bash string comparison

Posted on September 6, 2016 by ronaldpringadi

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465#!/bin/bash function test(){ echo "" echo "TEST $1" echo "VAR_1: $VAR_1 VAR_2: $VAR_2 " if [ "$VAR_1" = "false" ]; then echo " VAR_1 is false"; fi if [ "$VAR_2" = "false" ]; then echo " VAR_2 is false"; fi … Continue reading →

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Show postgres lock

Posted on July 21, 2016 by ronaldpringadi

You’re staring at a query that won’t finish, or a deploy that hangs on a migration, or a UI request that just sits there. Postgres is almost certainly waiting on a lock that another transaction holds. The classic query for … Continue reading →

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Apache Lucene: The Search Engine Hiding Inside Half the Internet

Posted on July 21, 2016 by ronaldpringadi

If you’ve ever used Elasticsearch, Solr, or even some features in big platforms like Twitter or LinkedIn, chances are you’ve been touching Apache Lucene without knowing it. It’s the quiet workhorse — a Java library that does one thing extraordinarily … Continue reading →

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