DO NOT EDIT THIS FILE! moinconfig/cspages/AlamodeAccessCaveatsAndWarnings!

Missing Libraries on An alamode Machine

Occasionally, you will login to an alamode machine and some course provided code will fail to run due some very bizarre reasons

ctb60-12$ ~khellman/SIMGRADING/Random 12345
/usr/lib/libssl.so: No such file or directory

Of course, libssl.so is there:

ctb60-12$ file /usr/lib/libssl.so /usr/lib/libssl.so.1.1
/usr/lib/libssl.so:     symbolic link to libssl.so.1.1
/usr/lib/libssl.so.1.1: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=5a12e36d18f5fd2e5519bd1f7741bcc6907bb3ad, stripped

This seems to be resolved by using a different alamode machine. ctb60-12 won't be fixed until it gets a reboot

Ugh, Too Many Passwords for alamode ssh Access

If you don't use Mines VPN software, then ssh(1) is your best bet:

1. First, setup ~/.ssh/authorized_keys properly on your jumpbox.mines.edu account

   remote$ scp ~/.ssh/id_rsa.pub MINESLOGIN@jumpbox.mines.edu:./remote.pub
   remote$ ssh MINESLOGIN@jumpbox.mines.edu
   :
   :
   jumpbox$ mkdir ~/.ssh
   jumpbox$ chmod 700 ~/.ssh
   jumpbox$ cat remote.pub >> ~/.ssh/authorized_keys
   jumpbox$ chmod 600 ~/.ssh/authorized_keys

2. Now you should be able to "bunny hop" through jumpbox to an alamode machine, if you don't have an authorized_keys setup on alamode yet, you are down to just one password... Test:

   remote$ ssh -J jumpbox.mines.edu ctb60-13.mines.edu

3. Now is the right time to setup some off-campus aliases in your remote machine to make life easier. Pick some alamode machine names (let's say you use ctb60-13, ctb60-19, and ctb60-07); everyone seems to have favorite remote login destinations, but for the life of me I don't know why... For each machine, add the following lines to your ~/.ssh/config file on your personal (remote) machine, adjusted of course for the machine names you've settled on.

   # on campus alias
   Host 13bb
   HostName ctb60-13.mines.edu
   User MINESLOGIN
   
   # off campus sweetness
   Host bb13
   Hostname ctb60-13.mines.edu
   ProxyJump jumpbox.mines.edu 
   User MINESLOGIN

   Now, from remote which is off campus and not on the Mines VPN, you should be able to do

   remote$ ssh bb13

   And connect directly to ctb60-13.mines.edu, but possibly with a password required.

4. If you were asked for a password, then setup authorized_keys in a manner analogous to that on jumpbox (notice how I'm using the ssh just configured in the previous step):

   remote$ scp ~/.ssh/id_rsa.pub bb13:./remote.pub
   remote$ ssh bb13
   :
   :
   ctb60-13$ mkdir ~/.ssh
   ctb60-13$ chmod 700 ~/.ssh
   ctb60-13$ cat remote.pub >> ~/.ssh/authorized_keys
   ctb60-13$ chmod 700 ~/.ssh/authorized_keys

   Since your ${HOME} is shared across all alamode machines, you have to do this on just one alamode destination. Test!

   remote$ ssh bb13 'hostname; echo Woot\!'
   ctb60-13.mines.edu
   Woot!
   remote$

You're welcome.

Grrr, I can't see the PDFs generated by grader.sh

Use a PDF viewer installed on the alamode images. Some examples include gview or evince; but xpdf is by the far the fastest.

$ xpdf output-1010.pdf

If you are ssh(1)ing into alamode, use the -X option.

remote-with-vpn$ ssh -X ctb60-13.mines.edu
ctb60-13$ gview output-1010.pdf

This even works if you bunny hop through jumpbox

remote$ ssh -J jumpbox.mines.edu -X ctb60-17.mines.edu
ctb60-17$ evince output-1010.pdf

Trace File Arguments Are Not Always Files

In practically all programming assignments, at least one command line argument is a file from which SIM should read random values from (in lieu of using a library specific pRNG). The TraceFiles page has sample files for use in development.

Beware that grader.sh scripts don't usually provide a static regular file as these arguments! Instead they use input redirection to connect a program generating a possibly infinite sequence of values to your SIM. This means that if you attempt to read all random values into an array or list, your SIM is going to "hang" --- it will dutifully read in an infinite collection of doubles until you exhaust machine memory.

An easy way to manage this is to create a TraceFile object that accepts a filename as a constructor parameter and provides a single getRandom() member function that returns a floating point value. Of simply write a getRandom( tracefile ) global function that accepts an open file descriptor (object, pointer, handle, the terminology depends on the language) and returns the next double from the file.

Why are things so complicated you ask?

By using redirection as the source for your SIM random numbers, grader.sh can be written with tests to be sure the random numbers are being used properly,¹ it is easy to incorporate pRNG streams into the mix without worrying about which language a student is using, and by providing fake sequence of random values...

$ ./SIM <(yes 0.5)

certain types of consistency checks can be automated without micro-managing how student programs are written.

Beware the VSCode IDE installed on alamode (Fall 2018)

The integrated terminal in the VSCode has been shown to be whacky when running Python code. If you choose to use this IDE, you are strongly advised to use a separate terminal window to test your SIM.