Lab1 Introduction to UNIX

During this week we will play-through the exercises refreshing your UNIX knowledge. Starting from the next week we start building the real serve-side service infrastructure. Therefore we find it critical for you to feel fluent with command line interface (CLI) of UNIX. The outline of this lab is as follows:

• CLI Intro
• Setting up CLI sandbox
• Trying out basics of bash shell
• Solving bash shell exercises

NB! In case are struggling understanding some of the abbreviations (or underlying terms), here are some references to read:

• UNIX
• CLI
• shell
• Linux
• GNU
• Bash
• VirtualMachine
• Live CD

CLI Intro

Command line interface interaction can be reduced to: typing in the desired command and reading or interpreting the corresponding output.

• Examples (assuming bash shell syntax, and GNU/Linux standard commands):
  • creating a directory:
    • mkdir dir1
  • listing the files in a directory:
    • ls dir1
  • renaming the directory:
    • mv dir1 dir2
  • copying a file
    • cp file1.txt dir2/file1.txt
  • navigating to the dir1
    • cd dir1
  • navigating one level up in the directory tree
    • cd ..
  • discovering the current directory (or current write directory (CWD))
    • pwd
  • removing a file
    • rm file1.txt
  • removing all text files (by *.txt extension)
    • rm *.txt
  • recursively removing all files in the current directory
    • rm -r *
• There many more commands we face during this lab (here we showed just few file management ones)

As you can see, working with CLI might feel not convenient, confusing and even dangerous, if lacking the basic CLI skills (the command showed in last example will remove all the files and directories from the current directory. There are many tutorials and best practice materials exists regarding the safe usage of the CLI. The truth is that just reading them is not enough without the practical exercises and while exercising we will eventually to errors, discover them and fix according to documentation. The question is if ruin the system once by misusing the CLI how we going to proceed afterwards ? It would be nice to have a kind of sandbox that would allow us to perform most of the CLI actions (even the dangerous ones) without damaging our actual system. Therefore we start our lab with building one ;)

Setting up CLI sandbox

In this section we are going to create the CLI sandbox for playing with the command line interpreter. We may refer to sandbox as an isolated environment or in case of UNIX command line we could just use the existing web based CLI emulators like the following one

• JSLinux

... however we find those a bit limited and in it turns out the best learning experience is to use the same OS we are going to install on our servers later. Therefore, we will use the VirtualBox VM instance to isolate the running Live OS of Debian 9.3 GNU/Linux. The setup like that has a number of advantages compared to web-based:

• Standalone (no Internet is required once the Live ISO is downloaded)
• Performance (no lags in console rendering due to hypervisor support)
• Isolation (the actual host system is not affected due to virtualization)
• Compact (no additional hard drive space required apart from Live ISO)
• Recovery (even if you manage to ruin the system all the changes might be reset to default by just restarting the VM).

Setting up the Sandbox-VM

Here we expect you have the basic Operation Systems (OS) skills, like those obtained during the course:

• Operating Systems LTAT.06.001

In class room we have the class PCs with pre-installed VirtualBox software. If you preferring class PCs, you can skip the next three sections.

Installing VirtualBox

If you prefer using your personal Laptop you may need to install the VirtualBox package:

• VirtualBox 5.1 Install Manual:
  • Windows 8.1 video
  • Windows 7 video
  • MacOS video
  • Linux
    • Refer to the next section

'''VirtualBox and it's alter natives for Linux users'''

If you are Linux user, you in fact do not need any additional work this lab. As you have the Linux (CLI) natively in your OS. You can use the bash shell of your Linux distro to solve the exercises of this week.
In case you want to have fresh environment (a sandbox) in order no to damage your own Linux while solving exercises of this week - you may consider the following options:

• Install VirtualBox package using the package manager of your Linux distro.
  • Once the VirtualBox package is installed, you should continue similarly to the Windows users.
  • Debian/Ubuntu/Mintu (deb-based)
    • # apt-get install virtualbox virtualbox-qt
    • ... or follow manual on VirtualBox page section Debian-based Linux distributions
  • Fedora/Suse/RHEL (rpm-based)
    • follow manual on VirtualBox page section RPM-based Linux distributions
  • Arch/Gentoo
    • you definitely know how to install VirtualBox :)
• Another option for you may be the Qemu/KVM emulator (alternative to VirtualBox):
  • detailed manual on Qemu/KVM you may read here

Enabling CPU-virtualization (Intel VT-x or AMD-V) features

In order to achieve better performance both VirtualBox and Qemu/KVM can rely on virtualization feature of the host CPU. The presence or absence of this feature depends on the CPU model and host Bios settings. Checking the feature state can be done as follows:

• In Windows video
• In MacOS manual
• In Linux:
  • # lscpu
    • and make sure in Virtualization entry there is VT-x value
    • ... if you do not have an lscpu command, make sure the util-linux package is installed
    • or use the command:
      • # cat /proc/cpuinfo |grep -E "vmx|svm"
      • ... and make sure either svm or vmx is in the list of processor flags.

NB! In case you do not have a virtualization flag enabled, you should enable it in the BIOS of your personal PC or Laptop. Reboot the Laptop and issue delete or F1 or F2 keys to enter the BIOS (usually there is a usage message viewed during the boot showing BIOS setup and other options).
NB! In case you cannot find the virtualization option in the Bios settings, it may be due to absence of this feature in the processor (check the specifications of the processor model). Both VirtualBox and Qemu can perform without it, the performance of the VM however might be slower.

Creating the VM

Next let's create VM suitable to run Debian 9.3 GNU/Linux. This newly created VM becomes our sandbox for playing with command line.
>>todo<< First of all download the ISO file of the distribution:

• Official Debian repository
• UT Local Copy

NB! Class PC users, please avoid downloading the ISO twice in case you find the corresponding file is present in the PC you are currently using.

Once the ISO downloaded and is valid, we may setup the VM (dependent on chosen emulator):

• For Qemu users:
  • in command line, start Qemu as follows:
    • qemu-system-i386 --enable-kvm -m 256M -cdrom debian-live-9.3.0-i386-xfce.iso -boot d
    • the options used here:
      • --enable-kvm forcing KVM hypervizer (CPU-virtualization feature has to be enabled)
      • -m 256M amount of RAM to assign for the VM
      • -cdrom debian-live-9.3.0-i386-xfce.iso install Live ISO file into VM's CD-ROM
      • -boot d force VM to boot CD-ROM first

• For VirtualBox users:
  • Open the VirtualBox application, and click New Button
    • Give a new VM a name SandboxDebian
    • Choose a type Linux
    • Choose version Debian (32-bit)
    • Click Next
    • Specify amount of memory 512MB, as this will be enough for testing purposes
    • Click Next
      • Select not create any virtual hard drives (we running Live CD - there is no need for storage)
    • Click Next
      • The warning should appear (telling no HDD is specified), but we agreed - this what we need
    • Click Continue
  • The newly created VM should be visible in the VM list (in the left in VirtualBox main window you should see SandboxDebian icon)
  • Right-click on it and select Settings
    • Go to System -> Processor tab -> select 2 CPU cores and Enable PAE/NX -> Acceleration tab -> Verify that Enable VT-x/AMD-V is marked -> Click OK.
  • Double-click on SandboxDebian VM in the list of VMs
  • During the first boot, the VM will ask to provide an ISO image to boot from
    • Provide the ISO file of the live version of Debian 9.3 which was downloaded.

Now we are ready to boot into Debian Live and start playing with CLI!

Booting Sanbox-VM and accessing CLI

After you have started the VM a Debian Live boot windows should appear:

• Please select Debian GNU/Linux Live (kernel 4.9.0-4-686) and hit Enter
• The standard boot process will take place and bring to a login prompt:
  • The default user for any Debian live is user with password live

Now we have the shell of Debian Live and we are ready to refresh our memory with Linux basics. In order to do so we heavily recommend working through the following tutorial:

• If your computer has Estonian/Non English keyboard It might be more convenient to install your native keyboard to the VM. There are 2 methods for doing it.
  • Method 1
    • there is a line:<property name="XkbLayout" type="string" value="us"/> in file .config/xfce4/xfconf/xfce-perchannel-xml/keyboard-layout.xml
    • in order to allow more layouts we need to modify this line adding more valueslike "us,ee"
  • Method 2
    • setxkbmap ee - estonian keyboard
• NB! Recommended for All
  • Learning the Shell by William E. Shotts, Jr. © 2000-2017
    • This one contains the well-detailed tutorial of the shell usage

In case you need more details about particular shell usage you may refer to:

• Bash Guide for Beginners
  • This one slightly larger but also detailed document about the bash shell usage
  • Recommended as a reference! When solving exercises you may quickly find the chapter to read through as the resource is having well organized index.

• Advanced Bash-Scripting Guide
• Shell scripting game
  • Just in case you fee bored by simple tutorials ;)
• Alo Peets' cheat sheet about Linux