Dotfiles and the Mathlab

Unix programs often store configuration options in a dot-file in your home directory (e.g., .emacs).

A quirk of the MathLab computers is that our home directory is erased every 48 hours. However, the machines are setup to run a script ~/MySBFiles/mybashrc each time you login, so we can use that to work around the home directory limitation.

Create a directory called dotfiles/ in your shared MySBFiles/ directory:

mkdir ~/MySBFiles/dotfiles

Create a file called mybashrc in your MySBFiles/ directory that will link the dotfiles into your home directory each time you log in. We’ll create this file in our home directory and then move it there, to be safe:

nano ~/mybashrc

Copy and paste the following into that file:

for dotfile in ~/MySBFiles/dotfiles/.*
do
   if [ ! -f ~/`basename $dotfile` ]; then
      ln -s $dotfile ~/;
   fi;
done

We’ll discuss loops and if-tests in the shell later, but there is one other new command we will note here: ln. ln -s creates a symbolic link to a file—it makes it appear as if these files are in our home directory ~/ when they actually live elsewhere in our path.

Tip

You can add other shortcuts or alias -es to you mybashrc file. A good thing to do is to also add:

alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'

This will force those commands to ask before overwriting or deleting a file.

Now save and move it to ~/MySBFiles/:

mv -i mybashrc ~/MySBFiles/

Now you should be able to put any configuration files into ~/MySBFiles/dotfiles/ and then will be linked to your home directory when you log in. We’ll need this later when we work with git.

Git configuration

Before we start using git we need to configure it. This will create a file ~/.gitconfig with global settings for using git.

First we need to tell git our name and email—this will be used in the log files when we make changes so other users know who made the changes.

git config --global user.name "name"
git config --global user.email "email"

where you replace "name" with your name and "email" with your email address.

Next we need to tell git which editor we are going to use. We’ll look at editors more later, but for now we’ll use nano.

git config --global core.editor "nano -w"

see https://swcarpentry.github.io/git-novice/02-setup.html#line-endings for other options.

Now, we want to ensure that this file is linked to our home directory when we log in:

mv .gitconfig MySBFiles/dotfiles/

Note: you might get a warning that it cannot preserve access times—that is okay.

To test this, open up a new terminal and do

ls -al

and make sure you see the .gitconfig file. It might look something like:

lrwxrwxrwx  1 mzingale domain users   66 Jan 30 10:19 .gitconfig -> /home/campus.stonybrook.edu/mzingale/MySBFiles/dotfiles/.gitconfig

The -> in the name shows that it is a link to the actual file stored in our MySBFiles/ directory.