Basic Sys Admin Material (top level)

The material we plan to cover in the Unix Sys Admin ed 5 text includes:

• Chapters 1-9, 11-13, 25, 29. Not all sections will be covered in class. We do not cover the sections of the text that are specific to non-Linux systems. Other sections of the book are covered later in our course, see the network and the security top level pages.

The following topics provide the basics of Unix. The majority of concepts are applicable to all types of Unix systems - further detals related to Linux are presented as well.

• Intro - chapter 1
  • Intro to Unix
  • Intro to Ubuntu (ch1)

• Booting/shutting down (ch2)
• Access control and rootly powers (ch 3)

• Controlling processes (Ch 4) (see also System Monitoring)
  • Command to see what's happening: ps, vmstat and top
  • signals, kill
  • Periodic processes, cron job scheduler
  • Unix scheduling(ch4)
    • Nice, renice (Ch 4)
  • Module 3 : OSConceptsAndApplicationToLinux

 

• Files and the Unix File System (ch 5)
  • structure
  • file types
  • file attirbutes - pemrission bits (see Access control)
    • commands: chmod, chown, chgrp, umask
    • setuid, setgid,sticky bit
  • chapter on file systems

• Adding Software in Linux (ch 6 )

• Scripting and the shell (ch 7)
  • Scripting philosophy
  • shell basics
  • scripting
  • regular experessions
  • Shells and Scripts (top level guide for the Advanced Learning Module on Bash Scripting)

• User management (ch 8)
• useradd, userdel,  passwd

• Data Storage (and Filesystems again), backups and recovery of data/disks (ch 20)
  • tar
• foremost - extremely useful at times....as it can help recover deleted files or examine a corrupted disk
  • sudo apt-get install foremost
  • See this link for an example of recovering a file you deleted
• Ubuntu information

 

• Display Devices, X-Windows, Desktop Environments, Remote Desktop
  • Display Devices -
    • Terminal windows -   provides access to a shell through the OS GUI
    • Virtual Consoles -  when Ubuntu boots in multi-user mode (yes....it is possible to boot in a stripped down, single user mode - we will discuss 'runlevels' later) it creates six virtual consoles
    • Issue: '$ps -aux | grep tty' on a dept. machine and we see 6 getty's. Actually there are 7, one is assigned to the console display
      • ps -aux | grep tty
        jmarty 646 0.0 0.0 11740 908 pts/1 S+ 08:39 0:00 grep tty
        root 1069 0.0 0.0 9476 860 tty4 Ss+ 02:22 0:00 /sbin/getty -8 38400 tty4
        root 1071 0.0 0.0 9476 864 tty5 Ss+ 02:22 0:00 /sbin/getty -8 38400 tty5
        root 1079 0.0 0.0 9476 860 tty2 Ss+ 02:22 0:00 /sbin/getty -8 38400 tty2
        root 1080 0.0 0.0 9476 860 tty3 Ss+ 02:22 0:00 /sbin/getty -8 38400 tty3
        root 1084 0.0 0.0 9476 864 tty6 Ss+ 02:22 0:00 /sbin/getty -8 38400 tty6
        root 1480 0.0 0.0 9476 860 tty1 Ss+ 02:22 0:00 /sbin/getty -8 38400 tty1
        
    • and then on our VM- our default configuration
      • root 826 0.7 7.1 420616 145644 tty7 Ss+ Feb02 6:29 /usr/lib/xorg/Xorg -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
      • root 829 0.0 0.0 23008 1768 tty1 Ss+ Feb02 0:00 /sbin/agetty --noclear tty1 linux
      • jjm 4776 0.0 0.0 21292 936 pts/18 S+ 08:32 0:00 grep --color=auto tty
    
    

• Unix has the concept of run levels - single user mode, multi user mode, multi user with GUI,
• Ubuntu server by default runs 'headless' meaning that a graphical user interface is not launched.

• X-Windows - The X Window System is a graphical windowing system that was developed in the early 1980's through a collaboration involving MIT, DEC, and IBM..
  • X11 (current short name for the X Windows System Version 11) , is a system that supports graphics devices and graphical user interfaces in a manner that 1)fits well in a Unix system; 2)provides an architectural system approach that promotes extensibility across a wide range of graphics and display hardware and devices as well as the higher level abstraction to support a wide range of desktop management environments.
  • X Windows is as tightly coupled to Unix as is the TCP/IP networking stack. All modern Unix Graphics Desktop Environtments run as the display manager component in the X system.
  • X11 provides a programming framework for graphics oriented applications.
    • Example X11 apps that are packaged with most Linux distros include: xterm, xeyes, xman, xwininfo, xclock
  • X11 is based on a client - server architecture. The server program is Xorg. Usually, the X client and the X server run on the same machine. However, with a few configuration changes at the server, an X client can run on a different computer. For security purposes, remove X11 apps are run over an ssh connection.

 

• Graphical User Interface, Desktop Environments
  • The Ubuntu default desktop environment is Unity which is based on GNOME.
  • GNOME is the most widely used graphical desktop environment.
  • GNOME is viewed as 'heavy weight' (i.e., consumes considerable resources), and so a number of lighter weight GDE's are popular - LXDE and Snappy Ubuntu Core to name a few.
  • Applications can be tty based or they can run in the desktop and make use of either the installed desktop or X Windows for graphics and desktop libraries.
  • Remote desktops ...
    • It is easy to run an X Windows application (i.e., a client in an X11 system) remotely - it communicates with the windowing services using TCP/IP.
    • Remote Display Protocol is a widely used Windows remote desktop protocol- Virtual Box VMs support a Virtual Remote Display Protocol (VRDP) which is backwards compatible with RDP.

• Logging (ch10)
  • systemd
  • syslog
• Monitoring (ch 29)
  • Logging (ch10)
    • key logs and locations
    • systemd
    • syslog
  • Intro to Splunk

• Drivers/Kernels (Ch 11)
  • Building your own kernel
    • Ubuntu page