Converting Floating number into binary

Refer to Binary Tutorial - 5. Binary Fractions and Floating Point 

Install NVIDIA Driver for Linux on CentOS 7 And Solve X Desktop Problem

Follow this guide: Install proper drivers for Graphic cards

Important: Issue caused X server when install nvidia driver

" Most important, what resolved the issue, is at the bottom of that first URL: Use the correct nvidia_driver_xx.run file, INCLUDING the flag --no-opengl-files (and select no when prompted whether you want an nvidia generated xorg.conf file)"

Installing Problem "You appear to be running an X server; please exit X before installing." and its solution

## stop gdm service and init 3
  261  systemctl status gdm
  262  systemctl stop gdm
  263  init 3
  264  sh NVIDIA-Linux-x86_64-390.116.run
  265  nvidia-smi

Reference: 

• "As the error states, you are still running an X server. This error occurs when you try to install the Nvidia .run files while logged in." 

Regenerate nividia driver

yum install dkms
# 418.87.00 driver version is found in /usr/src/nvidia-
dkms install -m nvidia -v 418.87.00

• Lost nvidia driver module and recompile from source: refer to for ubuntu and for centos 

Problem: X desktop has problem

Solution: 

1.  Enter BIOS setting and set OnBoard in Miscellenous Configuration 
2. DO NOT USE nvidia-xconfig and delete /etc/X11/xorg.conf ("The real question is why you want to create a conf file if it is working fine without one? What problem are you trying to solve?"[link]) 

Install MPICH on CentOS 7

Download: mpich download

Install guide: install guide or version 3.3.2 

操作记录：
  405  wget http://www.mpich.org/static/downloads/3.3.2/mpich-3.3.2.tar.gz
  406  ls
  407  tar xzf mpich-3.3.2.tar.gz
  408  ls
  409  ls mpich-3.3.2
  410  cd mpich-3.3.2
  411  ls
  412  ./configure --prefix=/opt/mpich-3.3.2
  413  make -j 2>&1 | tee m.txt
  414  make install |& tee mi.txt
  415  ls
  416  history

$ pwd
/etc/modulefiles

[root@localhost/etc/modulefiles]$ cat mpich/3.3.2
#%Module1.0#####################################################################
##
## modules anaconda/4.9.0
##
## modulefiles/anaconda/4.9.0
##
proc ModulesHelp { } {
        global version prefix

        puts stderr "mpich/3.3.2 - sets the Environemt for mpich/3.3.2"
}

module-whatis   "Sets the Environemt for using mpich/3.3.2"

set topdir /opt/mpich-3.3.2

prepend-path PATH $topdir/bin
prepend-path LD_LIBRARY_PATH $topdir/lib

How To Install Anaconda On CentOS 7

Refer to How To Install Anaconda On CentOS 7

Using module load command to switch environment for an application on CentOS 7

Refer to

• Software modules on CentOS 7
• Environment Modules – A Great Tool for Clusters
• Shell into modulefile 
  
  

For HPC:

yum install lmod-ohpc-8.1.18-6.1.ohpc.1.3.9.x86_64
# shell file into modulefile
/opt/ohpc/admin/lmod/8.1.18/libexec/sh_to_modulefile example.sh

Install it:

yum install environment-modules -y; bash

Examples:

root@beta  ## > cd /usr/share/Modules/modulefiles
root@beta ## > mkdir compilers
root@beta ## > cp modules compilers/gcc-4.8.5

"Then we edit the module info (compilers/gcc-4.8.5). The modified version looks like this:"

#%Module1.0###################################
##
## modules compilers/gcc-4.8.5
##
## modulefiles/compilers/gcc-4.8.5. Sample gcc module
##
proc ModulesHelp { } {
 global version modroot

puts stderr "compilers/gcc-4.8.5 - sets the Environment for 
      GCC 4.8.5 "
}

module-whatis "Sets the environment for using 
    gcc-4.8.5 (C, Fortran)"

# for Tcl script use only
set topdir /usr/bin/gcc
set version 4.8.5
set sys linux86

setenv CC $topdir/bin/gcc
setenv GCC $topdir/bin/gcc
setenv FC $topdir/bin/gfortran
setenv F77 $topdir/bin/gfortran
setenv F90 $topdir/bin/gfortran
prepend-path PATH $topdir/include
prepend-path PATH $topdir/bin
prepend-path MANPATH $topdir/man
prepend-path LD_LIBRARY_PATH $topdir/lib

Test it:

  988  module avail
  989  module help compilers/gcc-4.8.5
  990  cat compilers/gcc-4.8.5
  991  module whatis compilers/gcc-4.8.5
  992  module load compilers/gcc-4.8.5
  993  module list
  994  env
  995  env | more
  996  /usr/bin/gcc/
  997  env
  998  module unload compilers/gcc-4.8.5
  999  env

Ubuntu | Debian: Network Manager says Wifi "device not managed"

Refer to stackoverflow ""

wired device not managed

Most probably your interface appears in /etc/network/interfaces. By default, NetworkManager does not manage interfaces that appear in /etc/network/interfaces. You can change this behaviour.

To do this - in a terminal:

sudo nano /etc/NetworkManager/NetworkManager.conf

change the line managed=false to managed=true

Save, stop and start network manager:

sudo service network-manager restart

""

Install VNC Server on CentOS 7

VNC with Default desktop [Recommended]

Refer to:  

• Install and Configure VNC Server in CentOS 7 and RHEL 7 
  

## install vncserver
yum install tigervnc-server xorg-x11-fonts-Type1

## copy vnc systemc config file, :3 is an example, other number can be used
cp /lib/systemd/system/[email protected] /etc/systemd/system/vncserver@:3.service

## replace  with a user name
grep USER /lib/systemd/system/[email protected]
# 2. Replace  with the actual user name and edit vncserver
ExecStart=/usr/bin/vncserver_wrapper  %i

## change into 
# su - 
## run below command to set user's vnc password 
$ vncserver

VNC with XFCE 

Refer to 

• How to Install and Configure VNC Server on CentOS 7
• Using putty to portforward and encryption
• 
  

Beware xstartup file requires to unset variables SESSION_MANAGER and DBUS_SESSION_BUS_ADDRESS as below describles.

--------- Install necessary packages in root ------
  881  yum -y install epel-release
  883  yum groupinstall "Xfce" -y
  884  yum -y install tigervnc-server tigervnc-server-minimal
  885  history
--------- login to normal user ------------
	 # su - user
	1  ls
	## set password
    2  vncserver
    3  cd ~/.vnc/
    4  vncserver -list

       cp /etc/X11/Xresources ~/.Xresources

    5  cp xstartup{,.bak}
	## EDIT xstartup as below
    7  cat xstartup
#!/bin/bash

unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS

xrdb $HOME/.Xresources
startxfce4 &

For Ubuntu 16.04: How to Install and Configure VNC on Ubuntu 16.04 

For Ubuntu 18.04: How to Install and Configure VNC on Ubuntu 18.04