Computer Lab

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* [[#Changing settings | Not changing machine settings]]
* [[#Changing settings | Not changing machine settings]]
* [[#Storing files | Where to store your files]]
* [[#Storing files | Where to store your files]]
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* [[#How (and how not) to tell your students about our wireless network passphrase | How (and how not) to tell your students about our wireless network passphrase]]
 
== Special notes for instructors ==
== Special notes for instructors ==

Revision as of 19:23, 23 March 2015

We have a computer lab in the classroom, consisting of ten identical computers in roll-around desks. They are available for use by instructors and their students, and also by our members. This page documents how to use them, what software they've got, and how to request changes.

If you need to talk to us about particular CPUs, their names are the ten metallic elements from 24 to 33 in the periodic table: chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, and arsenic (Cr Mn Fe Co Ni Cu Zn Ga Ge As). Each CPU is labeled on the front with its name.

Contents

General rules

You must read and abide by the rules for using the classroom while you're using the computers. Pay particular attention to:

Your use of these computers means that you also agree to these policies at a minimum:

Also, note the sections below on:

Special notes for instructors

If you are an instructor teaching a new class, please see below about installing software---you can't install things yourself, and you must plan far enough ahead that we have time to schedule the installation in advance. Don't wait until the last minute.

If the students in your class might be using their own computers, please see below on how (and how not) to tell your students about our wireless network passphrase.

Finally, if we've installed software for you in the past, and you're repeating your class but it's been a while since it was last taught, please check with us to make sure that the software is still there and still works. We may occasionally upgrade operating systems---which could cause things to break---or remove software that hasn't been used in a long time to save space. It's wise to check as far in advance as possible to make sure your software is still there, still works, and isn't slated for deletion. Using the classroom

Setting up and putting away the computers

Each desk contains several cubbies:

  • A large cubby on the left, which holds a sewing machine. (If you're sewing, you're reading the wrong page.)
  • A large cubby on the right, which holds the CPU. Do not remove the CPU from the cubby.
  • A small horizontal cubby in the back, which holds the keyboard and mouse.
  • A larger cubby in the back, which holds the LCD monitor. The wifi transceiver is also attached to this.

Never disconnect any cables from any of the computers. You can set up and put away a computer while leaving everything connected.

Setting up

To set up a computer for use:

  • Go around to the back of the table.
  • First, pull out the keyboard and mouse and put them near the front edge of the desk.
  • Second, pull out the LCD and put it near the back edge of the desk.

Pulling the keybord and mouse out first is much easier than the other way around---the cables less likely to get tangled up while you're moving them.

The desks are designed to allow you to daisy-chain power from desk to desk by plugging each outlet strip into its neighbor. Don't daisy-chain all ten desks to each other, and don't plug the projector into a large string of desks. You will pop breakers on the outlet strips, probably about 20 minutes into whatever you're doing, when it's maximally annoying. For complete instructions on what to hook to what, read this carefully.

Abandoned machines

Please don't walk away and leave unsaved files and open applications. Saving your own files and closing applications before you walk away is your responsibility. If you don't do this, you leave later users in a quandry---can they shut down or reboot the computer, or not? Will you be back in five minutes or next week? And what should they do about unsaved files?

If you see a computer that looks abandoned and has unsaved files, don't save them. Why? Because you can't know whether the person who was editing them was making changes they really wanted, and you could overwrite a good version of, e.g., a CAD file with a version that isn't wanted. This is especially important because some random person could have poked at the file after the real user left and before you arrived, or character(s) could have been typed into it by accident, etc.

Putting away

When you're done with a computer, please shut it down and put it away.

It's important to shut it down for several reasons:

  • It guarantees you've thought about modified files, and haven't left it to the next person to make an arbitrary decision.
  • It saves power. (For several reasons, these machines are not set to sleep or hibernate.)
  • It reduces the chances that the machine will simply have the power yanked out from under it if someone unplugs (or blows a breaker on) an outlet strip it's daisy-chained to, perhaps several desks away.

It's important to put it away because the room is used for many other activities, and those activities might use the desks but not the computers.

You can shut the computer down via the operating system, or you can push the large power button on the front for about half a second only. (Don't just keep it held down---if you hold it for 4 seconds continuously, it will turn off the power immediately, without warning the operating system. Pushing it for half a second instead will ask the OS to shut down the machine gracefully. Note that, if there are still open applications, you may have to use the mouse to shut down instead---the OS will likely pop up a window complaining and asking what to do. This is another reason why everyone should exit all pplications before just walking away.]

Please leave the LCD power switch in the on position, even if you're turning everything else off. (It's okay to unplug the entire desk or desks if you want---just don't hit the off button on the LCD.) We do it this way because some of the LCDs have finicky buttons and it may be hard to get them turned back on, and because LCDs in standby consume very little power, assuming the desk is even plugged in at all.

Instructors may ask their students to put each computer away, or the instructor may put them all away, but you should not leave a classroom of computers all set up after your class unless someone has told you they'd like you to leave them set up.

To put a computer away, put the LCD in its cubby first. You may need to swing the screen down slightly to make it short enough to fit. Once the LCD is stowed, then stow the keyboard and mouse. You don't need to un-daisy-chain the power connections, because stowing and unstowing computers is more common than rolling all of the desks out of the way.

Hard drives and mechanical shock limits

Why are the computers all sitting on those squishy pads? Because they have spinning mechanical disks in them, and those disks have a shock limit of 4G even when they're turned off. The desks are also used for sewing machines, and some of those machines can produce quite a bit of vibration. The shockmounts are there to keep vibration from the sewing machines within the disks' 4G nonoperational limits.

The operational limits---how much shock a disk can take when it's actually on---are considerably lower. So if you see someone using a sewing machine---or doing anything else that could cause a lot of vibration---while the computer in that desk is turned on, please stop them and turn off the computer. For the same reason, it's a really bad idea to roll the desks around more than an inch or two if the disks are spinning---if you crash into another desk, or even run over a power cord you didn't see, the disk will not be happy. Having to recover a failed disk can be a lot of work, even with backups.

[If you'd like to volunteer to buy us 10 160GB+ SSDs to avoid this problem in the future, we would be more than happy to take you up on it.]

For more on how not to abuse the desks or the disks in them, see this discussion.

Do not disconnect cables

Do not ever disconnect any cabling from any of the computers in the classroom.

The sole exceptions are:

  • 120V power plugs from outlet strips, if you're moving desks around
  • Video from the one computer you're using to connect to the projector

We have found in the past that some people disconnect cabling from the classroom computers, such as network cables, leading to annoying and sometimes hard-to-debug problems for students and instructors taking classes. (For example, SolidWorks won't even start up without a working network, because it uses a network license.) Because this can interfere with classes, it is Asylum policy that no cables, with the exceptions above, should ever be unplugged from any classroom computers without prior permission from IT.

For more on why unplugging things is a bad idea, see immediately below.

In addition, if you have disconnected video from a computer in order to use the projector, you must reconnect it as soon as you are done with the projector. See above for why.

The computer lab is not for testing equipment

Do not test random equipment with our computer lab by unplugging bits of its hardware and then plugging in your own. If you have a computer you need to test with an LCD, or you have an LCD you need to test with a computer, don't do so in the computer lab. Find another, more expendable computer (ask us if necessary), or use your own. We say this for several reasons:

Inconvenience. It's been our experience that people who unplug any cables for any reason almost never remember to plug them back in, and when they do, they're often plugged into the wrong places (such as plugging not-quite-USB-3.0-compatible equipment into the USB 3.0 ports, leading to obscure and hard-to-debug flaky behavior). Many users think they'll remember, but experience demonstrates that they don't.

Damage. Unknown equipment under test could conceivably permanently damage one of the classroom computers. For example, failure modes that short 120V onto signal pins are not unknown. Hardware damage to one of the computers in the classroom is expensive to repair, not only in the money it takes to buy new parts, but in the personnel time required to buy the hardware, assemble it, and possibly reinstall entire disks full of operating systems, depending on what gets blown up.

Classes. These computers are constantly used for classes. They are critical resources. Having cables unplugged means that one or more students simply may not have a computer to use for that class, depending entirely on the skill of the students and instructor in debugging what went wrong. (For example, unplugging the network can lead to surprising failures; see above). Having one damaged by hardware experimentation means we can't run the class at full capacity until the damage is repaired. Either way, this leads to a very sticky situation, since people who have paid for a class would no longer be able to take it---possibly halfway through a set of several sessions.

For all these reasons, it is Asylum policy that the computers in the classroom are never to be used as test machines. The only exception to this policy is for well-behaved USB equipment (see below), and it is still a better idea to (a) go through a USB hub, and (b) use a more-expendable computer instead, unless this is part of an actual class.

Network

Because the desks roll around, the computers can't be on a hardwired Ethernet. Instead, each of them has a wireless USB device, which looks like a flash drive, plugged into a USB extension cable. That cable is attached to the LCD; it will often be sticking out just behind the LCD, or perhaps pulled a few inches out and flopping around a bit.

We do it this way for two reasons:

  • It gets the wifi transceiver far away from the metal case of the computer, which would otherwise act like a groundplane and absorb the signal
  • It gets the wifi transceiver higher up, where it's more likely to be line of sight to the wireless access point without metal obstacles in the way

Troubleshooting

If you're having issues with network on a computer lab machine, the first thing you should check is whether the wifi transceiver has a green LED that flashes occasionally. If it looks completely dead, it's probably unplugged. Check the connection right at the wifi first; that connection is frequently loose. (We've applied tape around the joint, but people sometimes disconnect the tape, believing that the wifi is instead a flash drive.) If that doesn't help, make sure the other end of the USB extension cable is plugged into the CPU. You can plug it into any of the USB ports except the blue ones, which are USB 3.0---the wifi drivers are unreliable using USB 3.0.

Never swap wifi transceivers between machines. They have unique MAC addresses. If you swap them, the machine will think it has new hardware, and it won't know that it can use the wifi passphrase that it already knows, which means it won't be able to get on the network. Even if you supply the passphrase for the new wifi transceiver, having the MACs swapped around will screw up remote administration of the machines. So don't do this.

(If you suspect that the wifi transceivers have gotten swapped, note that each one has the name of a chemical element writton on it in Sharpie. That should match the name on the front of the CPU.)

Hardware

Each CPU consists of a quad-core 64-bit AMD 4100FX, in a Gigabyte GA-970A-UD3 motherboard, with 8GB DDR3 RAM, and an nVidia GT216GL (Quadro 400) graphics card. The motherboard will accomodate up to 32GB of RAM, if that turns out to be necessary. Each machine also has 160GB of disk, shared across various partitions and operating systems.

Each computer has USB ports on the front and back panels. Most are USB 2.0 (red connectors), but two on the back panel are USB 3.0 (blue connectors). USB 3.0 is much faster than USB 2.0 and can provide more peripheral power per port, and is a good choice for flash drives, DVD drives, and portable disks. However, USB 3.0 support is relatively new industrywide, and not every USB peripheral works correctly with USB 3.0 drivers, so if you're having puzzling or flaky results, try it with a USB 2.0 port and see if things work correctly then.

If you're using these computers for hardware development, please be careful. If you're rolling your own USB hardware and there's any chance of miswiring your USB connectors or having unusual voltages on them, use a USB hub between your device and the computers! Replacing a blown USB hub is much easier and cheaper than replacing a motherboard, especially since the short market lifetime of motherboards means we'll probably have to buy a different type and deal with odd-man-out sorts of issues from then on.

The only sort of hardware development we support on these machines involves well-behaved USB devices, and you should see here and here for other rules involving disconnecting cables, and non-USB hardware, respectively. Even better, please use a different computer instead; ask us if you need a more-expendable test target.

Note: Due to deficiencies of the motherboards, these computers cannot boot from USB flash drives unless they are very specially formatted, which yours almost certainly isn't. This means that you can't boot other operating systems from USB unless you have an external DVD drive and a disk.

Operating systems

With a few exceptions (documented below), all ten machines are kept in a nearly-identical configuration, with these operating systems installed:

  • Windows 7 Home Premium 64-bit
  • Ubuntu Linux 12.04 Precise Pangolin LTS 64-bit desktop

Windows

The machines autoboot to Windows. When the machine comes up, it will automatically log into the user named "user". The other accounts on the machine are for administrative purposes. If for some reason you log out, you can just click on "user" again and you'll be logged back in.

Please don't reconfigure the machines, since not everyone shares your tastes, and some of those configurations are there for a reason. This includes things like the appearance of folders and windows, where the trash is, etc.

Linux

If you want to run Linux, reboot, wait 10-15 seconds until you see a message saying "Loading Operating System", and then wait until you see the GRUB menu. Use the arrow keys to select the top menu item instead of the bottom, and hit return. (Once you type any character at the GRUB menu, the countdown will stop, and the machine will wait for you to decide what to do.)

Once the machine has booted, select "guest account". Note that your settings and any stored files will vanish when you log out. (We may in the future switch to permanent accounts instead.)

Booting your own

In general, please don't. If you must, ask us first (classroom-installsREMOVETHIS@artisansasylum.com).

We say this because it's possible that booting an alternate OS can overwrite one or more of the existing partitions on the machine or the bootloader---even if you're not trying to install a new OS, some alternate OS's can be buggy. Such an overwrite could cost us an enormous amount of work.

But if you have permission to use an alternate that we trust, this is possible. Note that you likely can't do this from a USB flash drive, though. Under no circumstances are you allowed to write to any partition on the machine without prior arrangement---none of them are scratch or expendable.

Changing settings

Please don't. We don't want a war among various peoples' tastes, and some of those configurations are the way they are for a reason. See above.

If you absolutely must change some sort of configuration in order to make a particular piece of software run correctly, and the machine allows you to do so, send mail to (classroom-installsREMOVETHIS@artisansasylum.com) explaining what you did and why. Your change will likely have to be replicated to all of our machines to keep them in sync. Also, it will likely be lost if we don't know if it was done and the machine is ever restored from a prior backup. It's a much better idea to get us involved from the start to avoid any problems.

Storing files

In general, do not assume anything you leave on the machine will survive.

We may reconfigure or reinstall any machine at any time without warning. Every time any maintenance is performed on the machines, or any time an automated backup happens, everything on the desktop will be thrown away, as well as the contents of download folders and similar directories as well. (This keeps the backups smaller. Also, if such items were not regularly thrown away, people would get in the habit of expecting them to survive. That's a bad habit to get into, because (a) someone else could throw them them away at any time, (b) no one else would ever know if they could throw something away, and (c) there is no guarantee that anything in the local filesystem won't be wiped out at any time if the machine is restored from backup. Finally, expecting one's files to be on some particular machine sets up a dynamic where people need to bump others off "their" machine to get to their files, which is annoying to the people getting bumped.)

If you need to store files, you have two choices:

  • Use your own local storage, such as a flash drive or USB external disk.
  • Use our public file share, which is available to all members over the network.

Installed software

This section documents the software currently installed on the machines. If you'd like something installed, please see below.

Windows

We have Windows 7 Home Premium 64-bit installed. The packages below are what we've installed on all machines that aren't there by default out of the box.

  • Audio/Video/DJing
    • Ableton Live
    • Mixxx 1.11.0-alpha2
    • PureData 0.42.5
    • ASIO4ALL 2.10 [low-latency audio driver]
  • CAD/CAM:
    • Electrical
      • PCB design & schematic capture
        • FreePCB
        • TinyCAD
      • Hardware programmers and IDEs
        • Arduino 1.0
        • Cypress PSOC (Creator, Designer, and Programmer)
        • Fritzing
        • MATLAB
          • Image Processing Toolbox
          • Computer Vision System Toolbox
          • Control System Toolbox
          • Instrument Control Toolbox
        • Simulink
          • Stateflow
          • Simulink Control Design
          • System Identification Toolbox
    • Mechanical
      • AutoDesk 123D
      • Autodesk 123D Make
      • BigBlueSaw DXF exporter for Inkscape [gets units right]
      • Blender 2.63a
      • CamBam beta 0.8.2
      • CNCSimulator
      • DraftSight
      • HSMworks
      • Solidworks Premium 2012
      • ShopBot 3 Control Simulation (chromium only)
      • VCarve Pro ShopBot Edition 7.5 (chromium only)
      • PartWorks 3D for ShopBot (chromium only)
  • General productivity
    • BullZip PDF Creator
    • Firefox
    • LibreOffice
  • Graphics
    • Inkscape
  • Other
    • Cygwin 1.7.16-1
    • Processing
    • Wacom tablet driver 6.3.2-3

In addition, the packages below are installed on a subset of the machines. Typically, this is done for very large installations that will only be used by one or two people at a time; doing this saves a lot of work and allows us to distribute packages so we don't run out of disk space in the Windows partition. The computers on which the packages are installed are in brackets.

  • XPlane 10 [Cr]
  • Skannect and OpenNI for 3D Scanning [Ni]

Linux

We have Ubuntu 12.04 LTS (Precise Pangolin) 64-bit desktop installed. The packages below are what we've installed on all machines that aren't there by default out of the box and are generally useful by end-users. [Several small utility packages, including pv, socat, smartmontools, gparted, ntp, ethtool, and many others, are installed, but the entire list isn't worth documenting here. Note also that many major packages that are optional add-ons for Windows are included out-of-the-box in Ubuntu, such as Firefox and LibreOffice.]

  • General productivity
    • Emacs
  • Graphics
    • Inkscape

Installing software

If you're asking for an installation, please include the following information:

  • Which operating system you'd like the software installed on (Windows, Linux, both?)
  • How to find the software. (A URL going to the precise version you'd like is best, though for Ubuntu package installs, just naming the package is fine.)
  • Whether the software will be talking to any hardware, and if so, what.
  • Your deadline. More warning is always better.
  • Whether this is limited-time trial software, and, if so:
    • Its timing constraints
    • Your class size (in case we only want to install it on one or two seats)
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