ip_conntrack table full, dropping packet

Last week, I found myself with a server under low load, but it couldn’t make or receive network connections. When I ran dmesg, I found the following line repeating over and over:

ip_conntrack: table full, dropping packet
I’d seen this message before, but I headed over to Red Hat’s site for more details. It turns out that the server was running iptables, but it was under a very heavy load and also handling a high volume of network connections. Generally, the ip_conntrack_max is set to the total MB of RAM installed multiplied by 16. However, this server had 4GB of RAM, but ip_conntrack_max was set to 65536:

# cat /proc/sys/net/ipv4/ip_conntrack_max

I logged into another server with 1GB of RAM (RHES 5, 32-bit) and another with 2GB of RAM (RHES 4, 64-bit), and both had ip_conntrack_max set to 65536. I’m not sure if this is a known Red Hat issue, or if it’s just set to a standard value out of the box. Continue reading “ip_conntrack table full, dropping packet” »


ওমরাহর নিয়ম

১. ওমরাহর ইহরাম (ফরজ)
· পরিষ্কার-পরিচ্ছন্নতা সেরে গোসল বা অজু করে নিতে হবে
· মিকাত অতিক্রমের আগেই সেলাইবিহীন একটি সাদা কাপড় পরিধান করুন, অন্যটি গায়ে জড়িয়ে নিয়ে ইহরামের নিয়তে দুই রাকাত নামাজ পড়ে নিন
· শুধু ওমরাহর নিয়ত করে এক বা তিনবার তালবিয়া পড়ে নিন Continue reading “ওমরাহর নিয়ম” »


Understanding RAID

I always try to share what I learn, and a few days back was looking for a single page short cut summary notes on various RAID level for the storage units. Found this article quite resourceful and exactly a single paged document that I was looking for.

Now sharing the content for the readers. Enjoy!


raid-0 (1)RAID 0 splits data across drives, resulting in higher data throughput. The performance of this configuration is extremely high, but a loss of any drive in the array will result in data loss. This level is commonly referred to as striping.

  • Minimum number of drives required: 2
  • Performance: High
  • Redundancy: Low
  • Efficiency: High

Continue reading “Understanding RAID” »


GoodReads: How to use Docker in a practical way (part 1 – Introduction)

Part 1: Introduction to the terminology


It is not an uncommon situation, for early adopters of newly introduced concepts and technologies, to be totally confused when these can fundamentally change the ways of developing and delivering services. Especially when everybody talks about something like Docker, and how awesome and game changing it is. This confusion happens when we try things early on and rushing straight to testing them without grasping the whole concept and background of this newly introduced technology.

This is why you may have abandoned the whole trend of Linux containers, or because you read some controversial article from yea sayers and naysayers. In this first part, of a series of articles, we will try our best to clear things up and put everything on the right perspective for any developer, sysadmins, Q/A engineers or even enthusiasts who just need the right inspiration to use Linux containers and solve their special IT problems.
We will start from the beginning, with some necessary description of the historical events and concepts and then I will showcase how we can start working with Docker containers. This way, you will be able to understand “what led to the creation of containers”, “what are the building blocks” and “how do they work”. Continue reading “GoodReads: How to use Docker in a practical way (part 1 – Introduction)” »


Prophet Muhammad’s Last Sermon

Read it first in Bangla while was a school student, likely to be in my religion classes. Thought might be useful to other.

Prophet Muhammad’s final sermon was delivered during the Hajj of the year 632 C.E., the ninth day of Dhul Hijjah, the 12th month of the lunar year, at Arafat, the most blessed day of the year. There were countless Muslims present with the Prophet during his last pilgrimage when he delivered his last Sermon. Continue reading “Prophet Muhammad’s Last Sermon” »


Mustafizur stars in landmark series win- Bangladesh v India, 2nd ODI, Mirpur

216075Bangladesh 200 for 4 (Shakib 51*, Ashwin 1-32) beat India 200 in 45 overs (Dhawan 53, Mustafizur 6-43) by six wickets (D/L method)

Mustafizur Rahman was the hero in Mirpur again, (off)cutting through India’s batting with a six-wicket haul to add to his five-for on ODI debut, and launching Bangladesh to their first ever bilateral series win against India. Mustafizur’s 6 for 43, the second best figures by a Bangladesh bowler in ODIs, skittled India for 200, before Shakib Al Hasan steered the chase with a busy fifty, his second on the trot.

With this six-wicket win, Bangladesh also cemented their place in the 2017 Champions Trophy. An overjoyed Mashrafe Mortaza, who has been a part of each of Bangladesh’s five victories against India, toasted his team’s “big achievement”.

Why Bangladesh’s target was 200
When the rains came, India were already eight wickets down after 43.5 overs. Because the game was revised to 47 overs per side, India lost out on some batting opportunity, but that loss was minimal as they were already eight down at the time of the interruption. According to the DLS calculations, the batting resources denied to Bangladesh at the start of their innings, compared to what they would have had in a full 50-over innings, was marginally more than the resources India lost out on.

Continue reading “Mustafizur stars in landmark series win- Bangladesh v India, 2nd ODI, Mirpur” »


Pf vs Iptables- a Great comparative article

I enjoyed reading the following article, though would worth keeping a copy on my blog. Happy Reading-

Today I will be talking a lot about OpenBSD, FreeBSD and other Unix-like operating systems from the Berkeley Software Distribution. I thought that would be appropriate being my first document on Unixmen. I however will also be talking about Linux and Untangle and how they complement Unix based firewalls such as Pfsense.

I would like to explain what I think is the best way to secure a network from hackers and bots and why these techniques work as well as I say they do. I however will not be explaining how, as I will save that for another article. That being said if there is anything in error here please let me know but I am sure you will find nothing in contrast to common theory. I would also like to show you guys some things I like to do and things I think are critical to IT security. Continue reading “Pf vs Iptables- a Great comparative article” »


rkhunter perfect configuration


Exposing any computer to the internet is in some ways risky. There are many ways that your server can be compromised or attacked by remote systems and malicious software, and it is an ongoing and proactive process to defend yourself against potential threats.

One potential concern is rootkits. Rootkits are software secretly installed by a malicious intruder to allow that user continued access to the server once security is breached. This is an extremely dangerous problem, because even after the entry vector that the user originally used to gain access is fixed, they can continue to enter the server using the rootkit they installed.

One tool that can help you protect your system from these kinds of problems is rkhunter. This software checks your system against a database of known rootkits. Additionally, it can check other system files to make sure they are in line with expected properties and values.

In this guide, we will install and configure rkhunter to protect our Ubuntu 12.04 VPS. Continue reading “rkhunter perfect configuration” »


BD now member of Asia PKI Consortium

Bangladesh has been accepted as a member of the Asia PKI Consortium in its General Assembly (GA) Meeting held in Bangkok recently. The GA Meeting was chaired by Philip Leung, Chairman of Asia PKI Consortium and attended by member countries. The GA unanimously approved the membership of Bangladesh in the Asia PKI Consortium and expressed its interest to engage with Bangladesh in this complex field of technology, says a press release.

An international conference styled "The Common Denominators Collaboration of Cross-Region on E-Government Application, Cloud Computing and Security" was organised on the occasion in which large number international experts, companies took part Bangkok, Thailand recently. Ms Karen Chang, Office of Science and Technology, Executive YuanTaiwan and BAWG Chair along with Mr Shin Adachi, Dr Tschai Huei Jane and Mr Th Schee among others made presentations.

The Ministry of ICT of Thailand and Asia PKI Consortium (APKIC) were the hosts. The organiser of the event was Electronic Transaction Development Agency (ETDA) of Thailand, Business Case/Application Working Group (BAWG) of APKIC and Thailand PKI Association. Ms Suranghana Wayuparb, Chairperson of Thailand PKI Association & Vice Chair of APKIC Executive Director and CEO, ETDA along with Charamporn Jotikasthira, President of the Stock Exchange of Thailand and APKIC Chairman Philip Leung inaugurated the event. Continue reading “BD now member of Asia PKI Consortium” »


Miracle of Humankind- of the grace of Allah! Survivors after 17 days of building collapse

DHAKA, Bangladesh (AP) — A seamstress buried in the wreckage of a collapsed garment factory building for 17 days was rescued Friday, a miraculous moment set against a scene of unimaginable horror, where the death toll shot past 1,000.

Reshma survived, in remarkably good shape, by eating dried food that was in her area and drinking spare amounts of water with her. She was discovered on the second floor of the eight-story Rana Plaza building, where crews have been focused on recovering bodies, not rescuing survivors, for much of the past two weeks.

"I heard voices of the rescue workers for the past several days. I kept hitting the wreckage with sticks and rods just to attract their attention," she told the private Somoy TV from her hospital bed as doctors and nurses milled about, giving her saline and checking her condition.

"No one heard me. It was so bad for me. I never dreamed I'd see the daylight again," she said.

"There was some dried food around me. I ate the dried food for 15 days. The last two days I had nothing but water. I used to drink only a limited quantity of water to save it. I had some bottles of water around me," she said.

Once Reshma finally got their attention, the crews ordered the cranes and bulldozers to immediately stop work and used handsaws and welding and drilling equipment to cut through the iron rod and debris still trapping her. They gave her water, oxygen and saline as they worked to free her.

When Reshma was freed after 40 minutes, the crowd erupted in wild cheers. She was rushed to a military hospital in an ambulance, but her rescuers said she was in shockingly good condition, despite her ordeal.

Abdur Razzak, a warrant officer with the military's engineering department who first spotted her in the wreckage, said she could even walk.

"She was fine, no injuries. She was just trapped. The space was wide," said Lt. Col. Moyeen, an army official at the scene.

Reshma told her rescuers there were no more survivors in her area. Workers began tearing through the nearby rubble anyway, hoping to find another person alive. Continue reading “Miracle of Humankind- of the grace of Allah! Survivors after 17 days of building collapse” »