Month: May 2020

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Webinar – Build the Most Powerful Data Center with GPU Computing Technology and High-speed Interconnect

Build the Most Powerful Data Center with GPU Computing Technology and High-speed Interconnect

Date: Thursday, June 11, 2020
Time: 11:00am-12:30pm Singapore Time

Register here 

Please join NVIDIA as we discuss how to design a well-balanced system that maximizes performance and scalability of various workloads using NVIDIA GPUs and interconnect

Speakers will provide an overview of the state-of-the-art NVIDIA GPU accelerated compute architecture and In-Network computing fabric and how they come together with one goal: to deliver a solution that democratizes supercomputing power, making it readily accessible, installable, and manageable in a modern business setting. To learn more about this webinar click here

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“Command not found” Errors encountered in Gaussian G16

If you encountered errors when running Gaussian

bash: gview.sh: command not found

OR

bash: g16: command not found

OR

$g16/bsd/g16.profile: Permission denied

Usually it is due to the fact that the user is not in the Gaussian permission group.

Your GV and G16 folders should be in a unique Gaussian group. I have created a Gaussian Group called hpc_g16_group and put all the Gaussian users inside this group. Make sure the entire folder and sub folder of g16 and gv is using the same g16 group

drwxr-x--- 6 admin hpc_g16_group 4492 Aug 27 2019 g16
drwxr-x--- 10 admin hpc_g16_group 391 Feb 18 2019 gv

 

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Predicting the course of the COVID-19 epidemic in Poland

Virtual_ICM_Seminar_21May2020

TITLE: Predicting the course of the COVID-19 epidemic in Poland

SPEAKER: Franciszek Rakowski, affiliated Researcher at ICM University of Warsaw; principal Data Scientist at the AI institute, Samsung R&D, Poland

DATE&TIME: Thursday, May 21, 2020 at 4:00 PM (CEST)

PLEASE REGISTER AT:
https://supercomputingfrontiers.eu/2020/tickets/neijis7eekieshee/

ABSTRACT:
One of the most promising approaches to predicting the possible scenarios of the epidemic is based on agent-based models. The idea of that model family is quite simple: reproduce the demographic and sociological structure of the society, and run the simulations of the disease spread throughout that structure. The direct reproduction of the contact structure allows investigating the consequences of various administrative measures applied, like school closure or travel restrictions. The model results can be visualised as a dynamic map of spreading disease, and enables the assessment of burden of disease factors locally. Our model, constructed more than 10 years ago for influenza epidemics, has been reanimated and tuned to COVID-19 parameters. It is now producing both scientific results as well as pragmatic reports, which are then being passed to Polish governmental authorities.

SPEAKER’S BIO:
FRANCISZEK RAKOWSKI: Affiliated Researcher at ICM University of Warsaw.
Principal Data Scientist at the AI institute, Samsung R&D, Poland. Almost 10 years ago, when working at ICM UW as researcher, he led a project to construct a large-scale agent-based epidemic spread model for influenza disease. Recently, during the times of COVID-19 pandemic, he became the project leader of development and adaptation of the ICM Epidemic Model to the coronavirus disease. His interests also cover cognitive science, neuroscience and computational biology.

 

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SSH and X-Forwarding on CentOS 6

I encountered this error recently when trying to X forward to another remote site.

"Warning: No xauth data; using fake authentication data for X11 forwarding."

 

and there was no and doesn’t display picture.

These are the steps I took to trouble-shoot

  1. I checked my /etc/ssh/sshd_config and noted that the I have “X11Forwarding yes”
  2. On my .ssh/config, I have the “ForwardX11 yes”
  3. But one of my parameter /etc/ssh/sshd_config  “X11Uselocalhost yes”. Apparently,I was able to X11 Forward for hosts specify in my /etc/hosts file, but those outside my host file, I was not able to display the picture.
  4. But once I modified the  “X11Uselocalhost no”, the issue was resolved.

There was this post that a user explained quite well. (http://www.authsecu.com/nntp/comp-security-ssh/19540-comp-security-ssh-what-does-%22x11uselocalhost-no%22-do.htm)

When doing X forwarding, sshd listens on a TCP socket for connections from X clients. Normally, it will accept connections addressed to the loopback address only (127.0.0.1), restricting it to clients on the local host. X11UseLocalhost no means it will accept connections from anywhere. 

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Unable to open /dev/sdb with fdisk

Taken from my old blog Unable to open /dev/sdb with fdisk

Fdisk is a menu driven program for creation and manipulation of partition tables. The device is usually something like /dev/sda, /dev/sdb. A device name refers to the entire disks. /dev/sd? is the partition of the device. For example, /dev/sda1 refers to the first partition of the first device.

If you issued a command and you receive a corresponding message “unable to open /dev/sdb”

# fdisk /dev/sdb

 

Unable to open /dev/sdb

Linux is unable to locate or find the partition. One method to verify that it is so, do a listing of the

devices fdisk can see. In this example below, the partition has been created already.

# fdisk -l

 

Disk /dev/sdb: 2997.4 GB, 2997426536960 bytes
255 heads, 63 sectors/track, 364416 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1      267349  2147480811   83  Linux

WARNING: The size of this disk is 3.0 TB (2997400633344 bytes).
DOS partition table format can not be used on drives for volumes
larger than 2.2 TB (2199023255040 bytes). Use parted(1) and GUID
partition table format (GPT).

Once you have verified the presence of the device, do a fdisk /dev/sdb again

 

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xrdp_mm_process_login_response: login failed on CentOS 6

This post is taken from my old blog xrdp_mm_process_login_response: login failed

If you encountered this error xrdp_mm_process_login_response: login failed when you use the remote desktop connection to connection to a vnc session.

Even if you restart xrdp, the error still remain, the issue could be due to locked  X11 session that was created by xrdp.

To solve the issue, go to the/tmp/.X11-unix/ and find your X session and delete the session.

# cd /tmp/.X11-unix

Do a listing

# ls -l

Look at the session owned by you which you wished to delete

.....
.....
srwxrwxrwx 1 root      root  0 Jul  9  2012 X0
srwxrwxrwx 1 user1  users 0 Jan 25 09:13 X1
srwxrwxrwx 1 user2      users 0 Jul 10  2012 X10
srwxrwxrwx 1 user3     users 0 Feb 19 13:31 X11
srwxrwxrwx 1 user4  users 0 Nov 20 15:10 X12
srwxrwxrwx 1 user5     users 0 Jul 10  2012 X13
.....
.....

Delete the session……

If xrdp still fails, it seems that it is due to orphaned X–. Once xrdp hits an orphaned X– which may or may not be from other users, the error will still remain.

To see the orphaned X11 session, you can do a vncserver, which you will see something like that

# vncserver

 

Warning: Head-Node:1 is taken because of /tmp/.X11-unix/X1
Remove this file if there is no X server Head-Node:1

Delete all the orphaned X–
Restart the xrdp service and try the remote connection.

# service xrdp restart

If you are still having the issue, do look at alternative solution

  1. X Server — no display in range is available. xrdp_mm_process_login_response: login failed

 

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Fixing Authentication is required to set the network proxy used for download packages on CentOS 6

This was an old post from my dated blogger Fixing Authentication is requried to set the network proxy used for download packages for CentOS 6

I encountered this pop-up error today when I was xrdp into my CentOS 6. The error was something like this

authentication is required to set the network proxy used for downloading packages.  
An application is attempting to perform an action that requires privileges.  
Authentication as the super user is required to perform this action" and asking  
for the root password



Non-root users

Step 1: Launch a Terminal Console and type

# gnome-session-properties

Step 2: Uncheck PackageKit Update Applet .

See pix below.

Root User

Step 1: Disabled /etc/yum/pluginconf.d

# vim /etc/yum/pluginconf.d/refresh-packagekit.conf
[main]
enabled=0

 

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Making HTTP Server less vulnerable DOS Attack

**These steps were done on CentOS 6 Server

Step 1: Upgrade Apache HTTP to the latest version

# yum update httpd

Step 2: Edit the httpd.conf.

# vim /etc/httpd/conf/httpd.conf

Inside httpd.conf. Scroll all the way to LoadModule………. section and add the line

LoadModule reqtimeout_module modules/mod_reqtimeout.so

Step 3: Create a /etc/httpd/conf.d/reqtimeout.conf and put in the informationbelow

<ifmodule reqtimeout_module>
RequestReadTimeout header=10-20,minrate=500
RequestReadTimeout body=10,minrate=500
</ifmodule>

Step 4: To check whether the apache module is loaded, do

# apachectl -M

Or

apache2ctl -M

References:

  1. Mitigating WAS QID 150085 Slow HTTP POST Vulnerability on Apache