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This is a followup post to ealier post on Fedora Mount folders without requiring passwords Usually, mount folder permission is only available to root user. In order to allow this for normal user, we need to add a policy rule for polkit sudo vi /etc/polkit-1/localauthority/50-local.d/10-mount-without-password.pkla [storage group mount override] Identity=unix-user:madhur Action=org.freedesktop.udisks2.filesystem-mount;org.freedesktop.udisks2.filesystem-mount-system ResultAny=yes ResultInactive=yes ResultActive=yes Similarly, if you want to allow normal user to manage systemd units /etc/polkit-1/localauthority/50-local.d/service-auth.pkla [Allow yourname to start/stop/restart services] Identity=unix-user:madhur Action=org.freedesktop.systemd1.manage-units ResultActive=yes...

When writing applications for JVM which are long running such as application servers and web servers, it is very important to make sure that they shut down cleanly as and when required. This is very important in cloud computing, as cloud technologies such as Kubernetes might kill the pod due to low resources or as part of scale up / scale down processes. Similarly, applications deployed on VMs in AWS, Azure or GCE can be...

Web3 development scene is changing very fast with lot of breaking changes getting introduced every few months. This makes it very difficult to follow any online tutorial which was written few months back. This post itself will become obsolete after few months. As of this writing, I am using Solidity compiler version 0.8.15 pragma solidity ^0.8.4; In this post, I will outline few of the breaking changes I have encountered when working with web3 and...

We noticed that one of our production servers had an ever increasing memory usage increase. The memory increase was slow though. It looked like some of the keys didn’t had the TTL in our redis servers. We wanted to find out how. One of the standard ways is running the following command: redis-cli keys "*" | while read LINE ; do TTL=`redis-cli ttl "$LINE"`; if [ $TTL -eq -1 ]; then echo "$LINE"; fi; done;...

Recently, we noticed a production issue where some of the redis slave nodes were repeatedly being kicked out of the cluster. This was interesting since that redis cluster had been running without any issues for almost 3 years. The logs were repeatedly filled with slave trying to get full sync from master nodes again and again. # Connection with master lost. * Caching the disconnected master state. * Connecting to MASTER x.x.x.x:6379 * MASTER <->...

StatsD which is an excellent metrics aggregator, which can send aggregate and send metrics to variety of backends such as Graphite One of the aggregations which StatsD is generate an upper_99 and mean_99 for series of metrics. It is important to understand the differences between two. This is because if you are just measuring mean_99 , you might be missing on certain outliers which are important to understand the overall picture in the system. For...

Compared to Bitcoin, Ethereum provides a good set of development tools to get up and running with executing transactions in Ethereum blockchain. Here is an example of a simple transaction done in ethereum using Ganache The same can easily be modified to point to Infura var Web3 = require('web3'); var EthereumTransaction = require('ethereumjs-tx').Transaction; var web3 = new Web3('http://127.0.0.1:7545'); var sendingAddress = '0xaB549b951d2ebFd71B506bc14BF743A8879F5130'; var receivingAddress = '0x9E0F9ccA3B3FE51028660798c7bd6455bF9c3899'; web3.eth.getBalance(sendingAddress).then(console.log); web3.eth.getBalance(receivingAddress).then(console.log); var rawTransaction = { nonce: 1, to:...

Recently, few of our production server running Redis was exhibiting high memory usage. Strangely, redis was consuming very low memory, but the overall system usage was pretty high (> 70 %). One of the things which was common having this issue was that uptime of those systems was relatively higher than others. They were running without reboot for over 3 years. That’s when someone indicated that its the buffer memeory which might be full. What...

If you want to provision a test Apache Cassandra cluster for yourself, I recently created an automated solution using Vagrant and Ansible Git clone the repository https://github.com/madhur/vagrant-cassandra-ansible and use vagrant up command to bring up the five Ubuntu 18.0 nodes. This is a fork of original https://github.com/apkan/vagrant-cassandra-ansible, however it had couple of issues: It was using old version of Ubuntu which did not had systemd but instead used upstart Had 3 node cluster

With this pandemic and kids taking classes online from their devices such as Laptops and PCs, it is important that kids do not spend too much spend online and use PCs and laptops only for learning purposes. My own kid had started playing online games teaming up with his school friends over Google Meet / Zoom. These online games can be so addictive that having a conversation or arguing with your child does not work,...