How do you access specific programs?

Gaël Donval <g.donval@bath.ac.uk>

Balena is used for widely different things by widely different people. Installing programs system-wide, as you would on your computer, cannot work because of mutual incompatibilities. On Balena, we work around this problem using a so-called module system. From your perspective, almost every time you need to use a specific program, you need to load the corresponding module first.

Listing available modules

There are dozens of different modules readily accessible on Balena. You can list the modules currently loaded (i.e. in use) like so:

$ module list

You can also list all the modules available on the cluster using:

$ module avail

Use these commands as much as you want: if through the tutorials, the computer is complaining that a command is unknown, it is very likely because you forgot to load the necessary modules.

Loading modules

This is done by typing:

$ module load <module name or list>

All the program you will need are available in a special module repository loaded and displayed by typing the following commands:

$ module purge
$ module load group ce-molsim stack
$ module avail

You should now see a list of modules. The last section should contain something like music/std: this is one version of the MuSiC program that some of you are going to use. MuSiC can be invoked by calling:

$ music_gcmc --help

Bash should complain that music_gcmc does not exist: the relevant module needs to be loaded first…

$ module load music/std
$ music_gcmc --help

Note

Modules are loaded on a per-session basis: you basically need to load the requested modules every single time you connect to Balena.

Unloading modules

Though unloading modules is possible, it is not recommended. It is too easy to lose track of which modules are loaded or not. It is better to purge the module list to start afresh instead:

$ module purge
$ module load group ce-molsim stack

$ music_gcmc --help
bash: music_gcmc: command not found