Linux Online Virtual Environments in Teaching Operating Systems

Linux Online Virtual Environments in Teaching

Operating Systems

Olena Holovnia

[0000-0003-0095-7585]

Zhytomyr Polytechnic State University, 103, Chudnivska str., Zhytomyr, 10005, Ukraine

[email protected]

Abstract. The article provides an overview of Linux ready-made online

environments based on various virtualization technologies. Linux ready-made

online virtual environments are systematized, the advantages and disadvantages

of considering groups of online virtual environments are listed. The work also

gives the comparison of standalone online Unix/Linux terminals in terms of their

possible use for a course in operating systems. The author analyzes the

experience of teaching a Linux operating system to students of different

specializations, and in particular, discusses the virtualization tools used,

including Linux online environments (Amazon EC2, Cloud 9, a virtual machine

for NDG Linux Essentials course). The study states the need for developing an

individually designed system to provide Linux online virtual environments and

elaborates the requirements to this system. The work also discusses potential

challenges which the developers of Linux online virtual environments for

teaching operating systems may face, including the problem of finding a balance

between availability and stability of virtual environments on the one hand and

the realism of students’ learning experience on the other hand.

Keywords: virtualization, Linux, operating systems.

1 Introduction

A course in operating systems (OS) usually includes practical assignments on Unix-

like operating systems (particularly, Linux). However, at the same time, university lab

computers, students’ laptops and home desktop computers mostly come with Windows

installation. That is one important reason why different virtualization technologies are

often used for a course in operating systems. These technologies enable working with

a target operating system regardless of a locally installed operating system and without

compromising the security of university lab computers. Students, who take a course,

may come to class with their own laptops, as well as use lab computers, besides in some

circumstances they take a course distantly. So, hardware configuration, host operating

system, characteristics of network connections and other conditions vary widely.

Besides, students must get feedback on their practical assignments as soon as possible,

although this task could be challenging for small teaching staff working with a large

number of students during the semester. Some degree of automation on checking and

grading of assignments would decrease the amount of routine work and give teaching

staff the ability to pay attention to more creative assignments. In light of the above,

Linux online virtual environment running from a web browser could make practical

assignments more independent of software and hardware. It also could help students to

get well-timed feedback on simple mistakes.

There are numerous Linux online virtual environments with different characteristics

and different underlying technologies. Most of them could be at least partially used in

teaching operating systems. Conversely, although we generally appreciate the idea of

combining multiple virtualization tools for one course, there is still the need for a basic

tool to be applied most of the time.

The purpose of the article is to investigate available ready-made Linux online

environments based on different virtualization technologies and, thus, elaborate the

requirements to an individually designed system which provides Linux online virtual

environments.

2 Related work

Available works on development and usage of online Linux virtual environments vary

greatly focusing on different approaches as well as different courses’ needs. David

Croft and Matthew England [1] describe the experience using Codio at Coventry

University in teaching programming. Students use online virtual Linux environments

provided by Codio, while teaching staff add supplemental tasks with automated

feedback. David J. Malan [2] describes moving CS50, Harvard College’s introductory

computer science course, into the cloud provided by Amazon Elastic Compute Cloud

(Amazon EC2).

Bobby Powers, John Vilk and Emery D. Berge in the work [3] present Browsix,

posing it as a framework between Unix-like operating system and a web browser.

Browsix is emulating core Unix features using JavaScript. Rémi Sharrock, Lawrence

Angrave and Ella Hamonic [4] offer WebLinux tool providing a Linux terminal and an

integrated development environment (IDE) in the browser. In this case, Linux is also

emulated using JavaScript. Aristogiannis Garmpis and Nicolaos Gouvatsos [5] suggest

an online environment including emulated Ubuntu Linux operating system with

Graphical User Interface (GUI).

Nadiia Balyk, Yaroslav Vasylenko, Vasyl Oleksiuk and Galina Shmyger [6]

describe a virtual cloud laboratory based on Apache CloudStack and EVE-NG

Community and its use for teaching the CCNA Cyber Operations course. Andrii Ya.

Batiuk, Dmytro Ye. Vankevych, Hryhorii H. Zlobin in [7] focus on an experience of

using Proxmox VE along with OpenVZ virtual containers and KVM hypervisor for

Linux System Administrating special course.

Earlier, the study on the experience of teaching OS at higher educational

establishments of the world has been done [8], showing a number of common features

of analysed OS courses, including the following.

─ The high priority of studying Unix-like OSs (ranging from teaching OSs like PintOS

to popular full-function Linux distributives like Ubuntu).

─ The use of a wide variety of virtualization tools (from full emulators like QEMU to

type II hypervisors like VMware Workstation, VMware Fusion or VirtualBox, as

well as more specific tools like Vagrant, mCertiKOS or Cygwin).

─ In many cases, the availability of at least one alternative virtualization tool along

with the one applied by default.

All the above-mentioned studies have been analysed and taken into consideration while

elaborating the requirements to an individually designed system which provides Linux

online virtual environments.

3 Elaborating the requirements to Linux online virtual

environment for teaching the operating systems course

To formulate the requirements to the system which would provide Linux online virtual

environments we need to analyse the needs of the course, taking into account its

possible future development.

3.1 Previous theoretical and practical research

Our previous work [9] develops the methodology for using Unix-like OS virtualization

technologies in training bachelors of Informatics based on the varied approach to

applying before-mentioned technologies.

The approach involves combining several virtualization tools for meeting individual

features of a course, individual students’ needs and ensuring hardware and software

fault tolerance. The work specifies the procedure for selecting virtualization tools in

teaching OS to bachelors of Informatics. Following the suggested methodology, the

study also developed the Operating Systems and System Programming handbook for

future bachelors of Informatics and methodological guidelines Virtualization

Technologies in Teaching Operating Systems to Bachelors of Informatics for teachers

of higher educational establishments. During the implementation of the methodology

in Zhytomyr Ivan Franko State University (2016–2018) we have been using the

following tools.

─ Oracle VirtualBox

─ Amazon EC2 t2.micro instances

─ Cloud 9 IDE

─ Laptops with Linux (Ubuntu distributive)

The situation with Cloud 9 IDE is described in subsection 3.3. Amazon EC2 instances

were used as a supportive tool mainly because of low network bandwidth causing

considerable latency.

3.2 Reflection on recent practical experience

Later experience involved teaching two courses in operating systems in Zhytomyr

Polytechnic State University (from September 2019 till now).

The first course, Unix/Linux Operating Systems, was held from September 2019 to

December 2019 and was attended by third-year students of Computer Engineering and

Cybersecurity specializations.

The second course, Operating Systems, started in February 2020 and was attended

by second-year students of Computer Engineering, Cybersecurity, Software

Engineering specializations.

Throughout the mentioned courses, the students and the teaching staff were using

multiple tools for practical assignments. These tools are listed below and include both

locally installed applications and remotely accessed environments.

─ Virtual machine from NDG Linux Essentials course [10] (available on CISCO

Networking Academy)

─ Oracle VirtualBox

─ Laptops with Linux (namely Ubuntu and Arch distributives)

─ Amazon EC2 t2.micro instances (intermittently)

Experience of teaching these two courses revealed the need for a virtual environment

which would provide access to fully functioning Linux installation, supporting most of

the course practical assignments.

Concerning Unix/Linux Operating Systems course, virtual machine from NDG

Linux Essentials met almost all the requirements of the course, except networking (and,

thus, manipulating software packages) and the impossibility to save students’ files

between reboots.

According to the needs of our current courses in operating systems, the list of major

features an online environment should have is as follows.

─ The support of most administrative and non-administrative commands the typical

Linux installation would have.

─ Giving administrative privileges to students inside the virtual environment.

─ The support of basic networking operations (changing network configuration, ping

etc.).

─ The support of uploading/downloading files to/from virtual environments.

─ The ability to keep guest OS up-to-date.

─ The support of bash scripting.

─ The ability to save students’ files in guest OS between reboots.

3.3 An overview of available ready-made Linux online virtual environments

Online tools for working with Unix/Linux operating systems through the web browser

or other networking clients vary greatly depending on the functionality they provide,

conditions they are available on, underlying technologies et al. All the Unix/Linux

online virtual environments could be divided into the following groups.

─ Standalone online Unix/Linux terminals.

─ Online IDEs which include Unix/Linux terminals.

─ Full-function Unix/Linux virtual environments in the cloud.

Standalone online Unix/Linux terminals. These terminals are often free of charge.

They also are not necessarily based on a real OS kernel. A considerable part of

standalone online terminals emulates the effect of some commands through JavaScript.

However, other online Unix/Linux terminals are based on full emulators (e. g. QEMU),

and thus give the user more realistic experience. Examples: JSLinux [11], Copy.sh

Virtual x86 [12], Webminal [13], Linuxzoo [14] (based on full emulation), JS/UIX [15],

Weblinux [16], Browsix [17], CB.VU [18] (simplified emulation).

The Table 1 gives a comparison of different standalone online Unix/Linux terminals.

The main advantage of standalone online Unix/Linux terminals is their easy

accessibility. Among the disadvantages of these terminals are a limited set of

commands available, obsolescence, limitations of root access and/or of network access.

Furthermore, since most of standalone online Unix/Linux terminals appear to be

projects developed and supported by few enthusiasts, there are some doubts about the

future of these projects.

Online integrated development environments (IDEs) which include Unix/Linux

terminals. These tools’ main function is writing code. However, some online IDEs also

include Linux terminal with programming commands installed. Some other online

IDEs do not provide a terminal, but allow writing and running bash scripts. Root access

and networking from the virtual environment are usually provided in paid online IDE

services.

Examples: Codio [19], Cloud 9 [20], Codeanywhere [21], Paiza.io [22] etc. Among

the advantages of online IDEs is multifunctionality and usually more recent Linux

releases than in standalone online terminals. The disadvantages of these environments

include a stronger focus on programming than on administrating causing that some

components are not available.

IDE. Originally the service offered a virtual machine with Ubuntu Linux, full-function

terminal and an IDE for collaborative programming for all the registered users. Later,

due to numerous security violations from these virtual machines, the provider changed

the terms. According to the new terms, users have to connect virtual machines from

other services.

Full-function Unix/Linux virtual environments in the cloud. These environments

are virtual machines or virtual containers in the cloud, usually with administrative rights

and network available. Commonly such services conform to the IaaS model

(Infrastructure as a Service). Some of the IaaS services offer a long free trial period and

special programs for educational institutions. Examples: Amazon EC2 [23], Google

Cloud Platform [24], Microsoft Azure [25]. The main advantage of the full-function

Unix/Linux virtual environments in the cloud is access to most of OS commands,

including administrative and networking. The main disadvantage is that regular usage

is non-free.

Table 1. Comparison of standalone online Unix/Linux terminals

Service name

and developers

Virtualization / Guest OS Options

JSLinux,

Fabrice Bellard

Full emulator (compiled to JavaScript) /

Linux 4.12.0 (Buildroot), Linux 4.15.0

(Buildroot, Fedora 29)

Progress saving:

Yes, through

VFsync

Networking: Yes, bandwidth up

to 40 kB/s, up to two

connections per public IP

address

Root privileges: Yes

GUI:

Yes

CB.VU,

Colin Barschel

Very simplified emulator (JavaScript) /

None, emulates few Unix commands

Progress saving: No

Networking: No, emulates few

networking commands (e. g.

ping)

Root privileges: No

GUI:

JS/UIX,

mass:werk,

Norbert

Landsteiner

Simplified emulator (JavaScript) / None,

emulates limited number of Unix

commands

Progress saving: Partially yes

(demo version)

Networking: No

Root privileges: Yes

GUI:

Copy.sh

Virtual

x86,

Fabian Hemmer

et al.

Full emulator (compiled to JavaScript) /

ReactOS, FreeBSD 10.2, Oberon 2.3.6,

Arch Linux, KolibriOS, Linux 2.6,

Linux

3.18, OpenBSD, Solar OS; supports OS

images, uploaded by a user

Progress saving: No

Networking: Yes, in some cases

(e. g. Linux 3.18)

Root privileges: Yes

GUI: Yes, in some cases (e. g.

KolibriOS)

WebLinux,

Rémi Sharrock

Simplified emulator (JavaScript) / None,

emulates limited number of Unix

commands

Progress saving: No

Networking: No

Root privileges: Yes

GUI:

Browsix,

Bobby Powers,

John Vilk,

Emery D. Berger

Emulation of Unix abstractions through

browser API (JavaScript)

Progress saving: No

Networking: No

Root privileges: No

GUI:

Webminal Full emulator / Ubuntu Linux

Progress saving: Yes

Networking: Yes, with restrictions

Root privileges: Yes, in paid

accounts

GUI:

Yes, in paid accounts

Linuxzoo,

Gordon Russel

Full emulator (QEMU) / CentOS 7

Progress saving: No

Networking: No

Root privileges: Yes

GUI:

Yes, through Java VNC

3.4 The requirements for Linux online virtual environments for teaching the

operating systems course

The analysis of free ready-made Linux online virtual environments currently available

along with the analysis of an experience of teaching courses in operating systems

showed the need for an individually designed system to provide Linux online virtual

environments. The environments should meet the following requirements.

─ Realism. Linux, virtualized through the environments, should behave the same way

the real system would behave most of the time (throughout most of the practical

assignments).

─ Relevancy. The system should meet the requirements of the course.

─ Availability. Virtual environments should be available to all the students attending

the course after they had successfully proved their affiliation with the university.

─ Stability. Failures need to be addressed properly and within a predictable time.

─ Scalability. The system should be able to evolve for enabling new features or

supporting larger hardware capacity. New features we are particularly interested in

is the automation of simple assignments checking and grading (e. g. the correctness

of commands used).

─ Security. Security threats should be minimized. The effective mechanisms of

dealing with potential security breaches need to be developed.

However, the listed requirements pose serious challenges that need to be overcome.

The challenge of a wide choice. There are different virtualization technologies and

platforms that could be applied to complete the job. Analysing them and selection of

an appropriate among a great variety of options is a resource demanding task.

The challenge of implementing. Design, development and support of the target system

is another resource-demanding task.

The challenge of network isolation. The mentioned above problem of Internet access

from inside the online Linux virtual environment is typical for all virtualized systems

which are publicly available. Granting root/sudo access to students may produce serious

security challenges. The problem is greatly exacerbated if network access is also

provided.

The popular solution lies in making virtual environments isolated from the internet.

Students may reach virtual terminals via the internet to input commands (e. g. through

the web browser), but the internet access from within the virtual environment itself is

forbidden. Such an approach is entirely appropriate for teaching the vast majority of

Operating Systems course units, while it is inadequate for practising on network

configuration or installing software from network repositories.

Another possible solution to the network access problem is getting real personal data

of the online user, who works with virtualized OS remotely. Notably, cloud service

providers, giving virtual machines in the cloud with both root access and networking

available (Amazon Web Services, Google Cloud Platform, Microsoft Azure etc.),

affiliate user account with a valid credit card number. This does not guarantee the

legitimate use of an account, but facilitate investigation of possible security violations.

The third solution lies in giving students limited network access within the online

virtual environment (enough for testing network configuration). A local repository for

learning commands like apt may also be organized.

The challenge of a “playground”. Conversely, another question arises: will the always-

on system specially tailored for the learning needs be able to give students an

experience of dealing with some problems real administrators may face? We find it

crucial to find an optimal balance between stability and realism. Will such a

“playground” environment be enough to motivate students to continue learning Linux

after they finish the course? Given the foregoing, some assignments may be still done

using less predictable tools like VirtualBox-based virtual machines. This affects some

requirements for online Linux virtual environment. Namely, if certain assignments will

be done outside the environment, then:

─ a command-line interface may be enough for the online environment (even if the

course include assignments on the Linux GUI);

─ an implementation plan may start from isolated environments without the ability to

reach the network from inside out, as long as these environments may be easier to

manage on this stage.

The challenge of a transition. Besides the expenditure of resources on design,

development and implementation of the system, the latter will imply a phase of

transition. The transition from using tools described in subsection 3.2 to using online

Linux virtual environments could be smoothed by applying additional tools, which need

to be prepared in advance according to the varied approach mentioned earlier. These

additional tools may include some previously used tools (e. g. locally installed

hypervisors) as well as online Linux terminals (e. g. virtual machines from NDG Linux

Essentials course, Webminal etc).

4 Conclusions

The work has made a survey on Linux online environments based on various

virtualization technologies with the objective to elaborate the requirements to an

individually designed system which provides such environments.

Linux ready-made online virtual environments are organized into three major

groups: standalone online Unix/Linux terminals; online integrated development

environments (IDEs) which include Unix/Linux terminals; full-function Unix/Linux

virtual environments in the cloud. The main advantages and disadvantages of each

group, as well as a comparison of standalone online Unix/Linux terminals, is done.

We also analyzed our previous and current teaching experience to find out online

tools that proved efficient and the reasons why they still do not meet part of the course

needs.

The study concluded the need for designing and implementing a virtual Linux

environment with remote access to meet individual requirements of the Operating

Systems course. The virtual Linux environment should be realistic (supporting most

Linux commands through real execution, not imitation); relevant (meeting

requirements of the course); available (accessible through the internet, for everyone

who can prove his or her affiliation with the university); stable (failures should be

addressed effectively); scalable (support increasing hardware capacity, be able to

evolve); secured (security threats should be minimized, security breaches should be

effectively handled). Another point of interest concerns the partly automation of

practical assignments, including training and grading.

Future studies should focus on the investigation of virtualization technologies

suitable for Linux online environment, including private open-source cloud platforms.

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