Author Archives: ronaldpringadi

List open or listening ports

Posted on March 29, 2019 by ronaldpringadi

You started a service, you can’t tell whether it actually bound to its port, and you want to see what’s listening — or you want to find out which process is squatting on port 8080. Two one-liners, two operating systems: … Continue reading →

Posted in Bash, Operating System | Comments Off on List open or listening ports

MongoDB Notes

Posted on March 29, 2019 by ronaldpringadi

If you’re storing binary files inside MongoDB, the convention is called GridFS. It splits each logical file into two collections: a metadata document and a sequence of binary chunks. This post is a cheat sheet for inspecting and tweaking those … Continue reading →

Posted in Database | Comments Off on MongoDB Notes

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 →

Posted in Linux | Comments Off on CentOS 6 repo Settings

Show Linux Partition Tree Mountpoint and If SSD

Posted on June 27, 2017 by ronaldpringadi

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

Posted in Linux | Comments Off on Show Linux Partition Tree Mountpoint and If SSD

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 →

Posted in java | Comments Off on Setting log4j log level programmatically

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 →

Posted in java | Comments Off on Print java stack trace from anywhere

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 →

Posted in java | Tagged | Comments Off on Knowing your exception class name

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

Posted in Linux, Operating System | Comments Off on SELinux directory permission

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 →

Posted in Linux, Operating System | Comments Off on RedHat / Centos Firewall

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 →

Posted in Bash, Linux | Comments Off on Bash string comparison