Introduction to Linux in HPC/Various tips

This video covers a range of miscellaneous topics that are useful, but were not addressed before. For example, there are tools to print the space left on a disk or the recent command history. Other tools regularly execute commands for you or manipulate text. Finally, an overview of common package managers is given.

Video

( Slides as pdf)

Quiz

Does df show the size of a given file?

	No
	Yes

What does ln -s /tmp . do?

	Create a symbolic link of the current directory in /tmp
	Create a symbolic link of /tmp in the current directory named ./tmp
	Print a list of files located in /tmp and .

What is the watch command used for?

	To open a file of unknown format
	To regularly execute a command and see its output
	To watch video files

What are sed or awk used for?

	Manipulate and process text
	Set system configuration settings

How will you find a specific command in history ? HINT: use grep with history, how to use it?

Click and submit to see the answer

How can you compare two files and display a list of the difference? HINT: man diff

Click and submit to see the answer

Warning:

Please make backups regularly! Hard drives can fail on any computer

Exercises in Terminal

1. Find out the number of CPUs and amount of memory you have.

Answer:

     There are multiple ways to find out the number of CPUs and amount of memory on Linux computer. 
     the number of CPUs.
      1. lscpu: the following is an example output of the  lscpu command:

        CPU(s):                40
        On-line CPU(s) list:   0-39

     Brief description:
           CPU(s):                40: this computer contains 40 CPU cores.
           On-line CPU(s) list:   0-39: all 40 CPU cores are active.
      2. grep -c processor /proc/cpuinfo: This command uses  grep to count the number of lines that match  processor in  /proc/cpuinfo. The following is an example output:

        $ grep -c processor /proc/cpuinfo
        40

     As can be seen, there are 40 CPU cores in this computer.
     the amount of memory
      1. vmstat -s: the following is an example output of the vmstat command:

           196698736 K total memory
           4982596 K used memory

        vmstat reports the virtual memory statistics.
        The -s option displays a table for memory statistics.
        In this example there are 196 GB memory in total in the computer and 5 GB memory is used.
      2. grep Mem[TF] /proc/meminfo: This command uses grep to search for either MemT or MemF in /proc/meminfo and the following is an example output:

           $ grep Mem[TF] /proc/meminfo
           MemTotal:       196698740 kB
           MemFree:        113479460 kB

         As can be seen, MemT and MemF are matched by MemTotal and MemFree, respectively. The total amount of memory in the computer is 196 GB and there are 113 GB are freely available.

2. Permanently change your vim color scheme. 

Answer:

     Your personal vim configuration file is ~/.vimrc. In this file you can change the vim color scheme permanently. For example, the following setting uses the desert color scheme:
      colorscheme desert
     But beware of this permanent change of vim color scheme, because different color schemes may be preferred by different people. The vim color scheme recommended by others may not be the best choice for you.

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