Linux Notes: Linux Introduction and Caveats

  1. The information presented here is intended for educational use by qualified computer technologists.
  2. The information presented here is provided free of charge, as-is, with no warranty of any kind.
Edit: 2019-07-27

Introduction

Caveats

OpenVMS is just as fast on modern hardware as UNIX or Linux. Quick installation time, ease of use, and stability have convinced me that OpenVMS is the superior OS. On top of all this, OpenVMS does a much better job managing virtual memory (read on).

Linux has been the plaything of academia for a decades now which means it is much more feature-rich than proprietary operating systems, but it is not friendly. In fact it suffers from the problem of "too many chefs". What follows are a few examples of many.

Caveat: if you decide to enter the Linux world without a paid-up annual support contract then be prepared to support yourself. The self-help blogs are full of people "repeating the same mistakes" or "giving the same bad advice". Many do not appear to me to be seasoned computer professionals. At the very least you should read how Linux is maintained in IBM-managed data centers. You may also want to familiarize yourself with some of my real world Linux problems

Editing a file on Linux

Many Linux distributions use different commands to do similar things

The only thing common with the various Linux distributions is the name "Linux". For example, numerous Linux distributions use a different tool to partition a hard-disk. For example, check out the following list of commands to initialize then mount a disk under various operating systems

OS Details
Linux In Linux you must do the following (incomplete list):
  • use either fdisk or parted to partition the disk (and know why you would use one over the other; most Linux systems only support one of these commands)
  • use mkfs (then choose one of 50+ volume formats); I prefer mkfs.xfs for most Linux volumes but formats like vfat and NTFS are available for those people requiring compatibility with Windows
  • use xfs_admin to set the volume label
  • use mkdir /mnt/whatever     (to create a mount point)
  • use mount /dev/sda3 /mnt/whatever
  • edit /etc/fstab                      (to force an automatic mount during the next reboot)
  • caveat: newer Linux distros also support LVM (Logical Volume Manager) which can increase overall confusion.
Note: online help is meant for experts. Type "man mount" or "man umount" to see what I mean. 
Windows

Initializing then mounting a disk in Windows is mostly automatic

OpenVMS Initializing then mounting a disk in OpenVMS is done in two commands:
  • initialize the disk (struct=2 hails from the days of VAX/VMS):
       initialize/structure=5  disk-name:  volume-label
  • mount the disk:
       mount  disk-name:  volume-label
Note: online help is targeted at non-experts. Type "help initialize" or "help mount" from DCL to see what I mean

comment: For those of us who have worked on systems initially set up by the clueless, perhaps a less friendly software environment is desirable.

Installation

Software Updates (support, or lack of it)

Suggestions:

Customer-owned IBM-managed data centers

Hardware is relatively inexpensive in 2018 (compared with systems before y2k) and operating systems like CentOS-7 are free which changes everything. As I understand it, many customer-owned IBM-managed data centers are run like this:

Comparing Linux problems to other operating systems

I have been a VMS system admin since 1987 then started to work with OpenVMS in 1999. On VMS or OpenVMS, I have always been able to roll back an update. But this appears to be impossible (or at least very difficult) with modern versions of Linux in 2018.

CentOS-7

Windows

VMS / OpenVMS

comment: everyone reading this probably knows that software cannot be updated on most computer systems while it is being used. This is not true of OpenVMS where an active process has a run-time lock on some executable (like sys$exe:EDT.EXE;4 in the example above). But if your update is just copying in a newer version of EDT.EXE then it would be saved as EDT.EXE;5. Any process invoking EDT would pick up the new file while current processes could continue to use the old file. I have never seen anything like this on any other operating system. In fact, software engineers at DEC (Digital Equipment Corporation) developed this after running into problems on previous DEC operating systems like RSX-11 and RT-11

Recommended Books

There are so many Linux books available today that it is difficult to recommend any one over another. But for some reason, all the really good computer books in my library are from No Starch Press and it seems the same is true for Linux. These books can be purchased directly from www.nostarch.com , amazon.com and www.bookfinder.com

How Linux Works: What Every Superuser Should Know - 2nd Edition (2015) Brian Ward

The Linux Programming Interface (2010) Michael Kerrisk
A Linux and UNIX System Programming Handbook

External Links

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Neil Rieck
Kitchener - Waterloo - Cambridge, Ontario, Canada.