Direnv

direnv is a program that acts like a plugin for your shell. Specifically, "it augments existing shells with a new feature that can load and unload environment variables depending on the current directory." Beyond environment variables direnv is useful for automatically loading and unloading any environment that is associated with a particular directory/project. Please see [1] for basic setup and usage of direnv; it is already installed on babel servers, so that step can be skipped in setting it up. NB: Do not create or allow .envrc files in shared directories; this can cause problem for you and/or other people.

Activating conda environments

The primary use case for direnv on babel is easy conda environment activation without the need to activate a conda environment in your .bashrc file, as this can cause your shell to hang when you SSH into the cluster. Instead, you can have direnv activate your conda environment for you when you enter into the directory of the relevant project. This doesn't make conda any faster, but it prevents your session from hanging on login. Also, it saves you the trouble of having to manually activate and deactivate your conda environments.

As conda environment can be activated by adding the following to ~/my_project/.envrc (for example):

 eval "$(conda shell.bash activate my_environment)"

Make sure to direnv allow to permit this .envrc to take effect. If you no longer need conda to activate immediately at every login, you can execute:

 conda init --reverse

This will remove the conda-activating code from your ~/.bashrc which can cause the login into hang. If your SLURM jobs are no longer able to find your conda environent (i.e., because your ~/.bashrc no longer does any conda stuff), you can run the above eval ... in your scripts. If you are only running a Python program, you can also just run ~/miniconda3/env/my_environment/bin/conda without activating anything (assuming that is where your conda enviornments are).