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Linux resources for remote teaching

General info

  • All solutions that involve the use of the university’s systems, both remotely and locally, depend on shared infrastructure. The IT Division does its utmost to ensure that all services are available and in operation, but sometimes things just don’t work out. Help us by planning such that extra time is available if needed, and by registering support cases, even for relatively minor problems.
  • Avoid creating peaks in the use of resources – this means that we can do more with the resources we have. During termtime, the use of resources tends to be highest during lab sessions, which are timetabled for 10 am-12 noon and 1-3 pm. Thus solutions that move users to early in the morning or late in the afternoon are to be preferred where possible.
  • It is possible to mix solutions; different solutions are more suitable for different course components and different student groups.

Several alternatives

Resources that are available at LiU for remote teaching under Linux are described below.

RDP

The remote desktop protocol, RDP, was developed in the Windows sphere, and is a popular way to control Windows computers remotely. It is fortunate that third-party servers are available for Linux that use the same protocol, which makes it possible for us to offer RDP access to Linux computers via https://rdpklienter.edu.liu.se. It is important to remember that the computers that are available for RDP connection are also standard computers in a computer lab, and they can be booked for teaching sessions in the lab. It is possible under Linux for other people to use RDP on a computer at the same time as a student is physically sitting at the computer (which is not possible under Windows).

An RDP connection makes it possible to use a computer in the computer lab, with exactly the same software and performance. Some important points to consider:

  • Students from sessions booked in TimeEdit have priority, and must always be able to work.
  • It may be difficult to use software that requires graphics with hardware acceleration. Test any software at an early stage; it’s possible that it works excellently.
  • The computers in the computer labs are multi-user systems, and if two or three students are logged on to the same computer they may disturb and block each other. (This problem is, however, smaller than it is for ThinLinc.) The computer is a shared resource, and this means that, among other things, the CPU, memory, network and open TCP/UDP ports are available to all who are logged on to it.

In order to use RDP, the person who has booked the computer lab in TimeEdit must consent. Alternatively, you can use RDP if you have booked the lab yourself. There are no technical barriers to using RDP, and the service is based on the idea that everyone collaborates and follows the timetable. The person who has booked the computer lab has exclusive access to the computers, unless otherwise agreed. Thus, it is possible to use the lab via RDP after agreement with the person who has booked it. Remember that the person who has booked the lab in TimeEdit has priority, and other users must be careful not to disturb the work.

Load balancing

RDP does not have any facility for load balancing – students can connect freely to any computer they select. The responsibility for distributing computers among students lies with the course personnel, who should aim to have approximately one RDP session per computer. Remember that students who remain behind after a lab session may disturb the next session, just as is the case in physical teaching sessions.

ThinLinc

ThinLinc is, just as RDP, a tool for graphics-based remote connection. The major difference with RDP in our case is that many users use ThinLinc to connect to a limited number of physical machines. In contrast to RDP, ThinLinc uses load balancing. Users connect to thinlinc.edu.liu.se using a client that can be downloaded from the manufacturer’s website. ThinLinc also has some important functions that RDP does not have, such as support for seamless multi-monitor use.

 

LiU experienced problems with thinlinc.edu.liu.se during the autumn of 2019 and spring of 2020, but the situation has improved significantly, as seen in our case history and in an analysis of logfiles. The most significant measures to improve the situation have been the change of desktop environment from Mate to Xfce, and several patches to the software (which had not been designed for as many users of one system as was in fact the case). During the realignment to distance mode, the cluster was increased from 4 to 8 machines. The cluster currently has capacity for 250 simultaneous users, which can be increased if required.

ThinLinc is not a resource that can be booked, and many students use the service for independent study and project work. These are what we recommend that ThinLinc should primarily be used for. It is possible to conduct timetabled teaching via ThinLinc, but this is not what the system was designed and built for.

The ThinLinc environment can be used in the same was as a standard computer in a computer lab, with some exceptions. These include:

  • It may be difficult to use software that requires graphics with hardware acceleration. Test any software at an early stage; it’s possible that it works excellently.
  • Tasks that require much calculating power, such as FEM simulations, TSP problems, and the compilation of large projects will disturb other users. The rule of thumb is that tasks that take less than 20 seconds on a laptop can be executed without needing to take any special considerations. The rule of thumb becomes more complicated when multithreading is used – reasonably long single-threaded tasks are OK, while multithreaded programmes that occupy all available cores should only be run in extremely short pulses. The same is true for memory – simply because a machine has a few hundred gigabytes of memory, this does not mean that you can use as much as you like.
  • Performance measurements will often show large variations. Certain lab sessions contain tasks in which the students are to measure performance: one example of this arises when they are to determine how well an algorithm performs. Since many others are using the systems, the measurements will be affected not only by the system’s background processes, but also by other users.
  • TCP/UDP ports are an unprotected shared resource. If a lab session or software run requires listening to a specific port, only one student at a time will be able to use the port. All others will be able to talk to the port. For certain software packages, it is possible to configure this at start-up, while it is hard-wired for others. Investigate this well before the lab session is to start, and contact the IT Division if it is necessary to change the configuration of the software.

If lab sessions that require significant calculating power are arranged, it is often necessary to use a dedicated resource such that other users of multi-user systems are not disturbed. Contact the IT Division for help to plan such sessions, if it is not possible to book a computer lab.

SSH

An extra resource is available at ssh.edu.liu.se, to which connections can be made using SSH. This is an excellent solution if all that is required is a terminal window. If this is the case, SSH is strongly recommended. If, however, graphics-based programs are to be used, ThinLinc or RDP should be used. It is possible to run graphics-based programs via X-forwarding, but it is less convenient for the user and uses significantly more resources than RDP or ThinLinc. Otherwise, SSH has similar disadvantages as ThinLinc – it is a shared resource, even if the number of users is smaller.

Own computers

For certain lab sessions, an excellent alternative is to help students install the software on their own computers. There are major advantages to this – the students are not dependent on the university’s infrastructure and having a functional network connection. Furthermore, the use of resources is transferred from the university’s shared resources to the students’ own computers.

Points to consider:

  • The content of student laptops differs widely. Both Windows and OS X are popular. Many use Linux, often the Ubuntu or Arch distributions. This means that the software to be installed must be available for many different platforms. In addition, the software will behave differently on different platforms.
  • Now that Windows Subsystem for Linux, WSL, is available, the situation has improved somewhat.
  • Software can sometimes be difficult to install by oneself, or under certain operating systems. Make sure that you test the installation in advance, and provide detailed instructions for the students.
  • Allocate time to help students with software installation.
  • Students have a wide range of computer skills, some students are extremely capable while others are considerably less so.
  • The students’ computers also have limited resources.
  • Be prepared for a situation in which certain students use ThinLinc instead of installing software on their own computers.
  • It is often not possible to install software for which the university has purchased licences on the students’ own computers. It is possible, however, in certain cases, including software packages for which students can obtain licences through https://minit.liu.se. This page shows the software for which students can obtain licences.

Virtual machines

If it is desired to have the students run software locally in a ready-to-use Linux environment, a possible solution is to distribute virtual machines, with the aid of, for example, VirtualBox. This has several major disadvantages that you should be aware of.

  • It is not trivial to transfer files into and out from the virtual machine. This means that you can expect students to run complete lab sessions using files in the virtual machine, without taking a backup. Encourage them to take backups, or use a version management system in, for example, https://gitlab.liu.se.
  • It is difficult to update a virtual machine when students have started to use it. Test everything thoroughly in advance!

 

  • The IT Division can provide info and advice here, but cannot provide support for this solution.  It’s a good idea to open a support case at the IT Helpdesk to obtain advice and discuss ideas.
  • It is not possible to use certain resources in the LiU network, including central file storage and licence servers. Even though some of these problems can be solved from a purely technical point of view (by using a VPN, for example), we advise against this very strongly when using a virtual machine.
  • Some students have computers that cannot run a virtual machine.
  • The user experience when using a virtual machine is not optimal.
  • The problem of distribution must be solved – how are the students to obtain the virtual machine?

General advice

  • Do not transmit any confidential information, such as passwords.
  • Install the machine such that users are automatically logged in at start-up.
  • Give proper consideration to passwords and access rights! It will probably be necessary at some point for the users to enter the account password. Should users be able to use the root account?
  • Construct the machine to be as small and unobtrusive as possible. We recommend that the construction be based either on Ubuntu Server 18.04 LTS with a minimal Xfce environment or on Xubuntu 18.04.
  • Make sure that the machine is fully updated when it is distributed to the students. It’s a good idea to activate automatic security updates.
  • Be careful when using commercial software – do not contravene any of the licensing conditions.
  • Ask the students to download and test virtual machines well in advance of the first lab session.
  • Contact the IT Division for information about the easiest way to distribute the virtual machine to the students.

Prohibited use

Since many of the resources described above are shared resources, it is important that we work together and use the resources in such a manner that we do not disturb other users. A common example of behaviour that disturbs others is the execution of intensive and long calculations over ThinLinc. We would prefer to avoid strict limits on resources, since these cause other problems. Users who use shared resources in a manner that disturbs others may find that the session is terminated without prior notice. Help the students to avoid causing problems!

Summary

We summarise here some important points to consider when deciding which teaching methods to use during the autumn term. If you have any questions or concerns, create a case at helpdesk@liu.se.

RDP

RDP is an excellent alternative if the use of resources can be coordinated with those teaching in the computer lab. In order for the resource to be used as efficiently as possible, its a good idea to use RDP for courses in which the students are expected to work hard during timetabled lab sessions, and maybe not so much outside of timetabled teaching. RDP is a powerful resource – but its use must be planned.

ThinLinc

ThinLinc is a resource that is shared by significantly more users than an individual computer in a computer lab. For this reason, it is important not to create peaks in computer use. It is recommended that courses in which the timing of lab sessions is more flexible, such as project-based courses, use ThinLinc.

SSH

If the users are to use solely text-based tools, we strongly recommend using SSH (via ssh.edu.liu.se). SSH has a limited field of use, but it functions extremely well in this field.

Virtual machines

Virtual machines are powerful tools, but require a lot of work, have limited support at LiU, and considerable potential for failing to work properly. Unless using a virtual machine really is the only possible solution, RDP or ThinLinc are probably better alternatives.

Own computers

Having the students install software on their own computers is often the best alternative. This is, however, sometimes not possible or too complicated.

IT's Helpdesk

Contact Helpdesk for IT support:

Opening hours

Regular opening hours:
Monday and Thursday 8 am – 6 pm
Tuesday, Wednesday and Friday 8 am – 5 pm


Page manager: karin.linhardt@liu.se
Last updated: 2020-08-10