It starts from my needs to have both version 2 and 3 Python run in my machine, as Python2 is set to be retired by the community in 2020, however, lots of the work needs to be maitained at Python2 to ensure a smooth transition. That’s why I am looking for a solution, which further leads me to dig into operating system, in particular, Linux.
Professor Arif Butt’s series of video is quite thorough even with a bit of middle east accent. He organizes his teaching into the following modules.
Basic Shell Commands
Bash Shell Further
Hard and Soft Links
Special File Permissions
Access Control Lists
Managing Services Using Systemd
Linux Log Files
From his lecture, we first get to learn the infrastructure of computer from top down, OS on VM, Virtual Machine, and VM on top of Hypervisor (VM monitor), Hypervisor on top of OS on top of physical hardware.
There are two types of hypervisors – Type I and Type II hypervisors. Type II contains: Oracle Virtual Box, VM Ware, Solaris Zones, MS Visual PC, and QEMU. Since the creation by Linus. There are multiple Linux Distributions too: RedHat, Fedora, Ubuntu is most popular, CentoOS, and Debian also pervasive.
Internal command such as cd exit type help, they are part of the shell program itself. while external command is a command hwose code reside in a fiel on disk. e.g., clear, ls, passwd, man.
Not like windows file system, of which we are familiar with C drive, I drive etc, in Linux, everything is stored in root directory, enterrable by cd /, and bin bin directory, containing all user related commands. There are
- Binary directories such as sbin diectory, lib64, opt directory for optional software, mostly are empty;
- Configuration directories include boot directory;
- Data directories are home, root, srv, media, mnt and temp directory. media directory for media software such as CD etc.
- In memory directories such as proc (contains names are PID of process), dev, sys, they are not reside in memory.
- System Resources directory, /usr/
- Variable Data directory /var/ contains file with unpredictable size