Rafael Cavalcanti

Linux enthusiast and human being.

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A way to organize your Bash aliases on multiple hosts
Aug 27, 2018
4 minutes read

If you use multiple systems, you probably have a method of syncing your dotfiles between them. But different systems also have different needs.

When we talk about Bash, not properly managing those differences, could mean having tons of useless aliases polluting your environment, just because they are wanted on other machines. Or a very cluttered ~/.bash_aliases.

On this post, I’ll talk about my approach to handle different Bash aliases on multiple machines.

Some solutions

A first try to handle the differences between hosts is, obviously, throwing some conditionals to your ~/.bash_aliases. For example, if you have aliases to cd to important directories, you could condition them to the existence of the folder. I do this to some extent and helps to keep the environment clean.

However, it only works to a certain point. When you deal with systems that serve totally different purposes, say a Raspberry Pi server vs. your laptop, this method becomes cumbersome. Your ~/.bash_aliases will be filled with conditionals, some maybe with difficult logic, and badly organized. Not to mention giant.

An alternative to this is to have multiple copies of your aliases file with the needed differences, and point each machine to the correspondent copy. The advantage here is that you have more readable files, but in the other hand, tons of duplication and management hell. Not nice either.

So, let’s talk about my approach.

My approach

# ~/.bashrc

# Alias definitions.
if [ -f ~/.config/bash_aliases/$HOSTNAME ]; then
  . ~/.config/bash_aliases/$HOSTNAME
else
  . ~/.config/bash_aliases/default
fi
~/.config/bash_aliases
├── base        # Common aliases
├── default     # Aliases for generic hosts
├── foo         # Aliases for host foo
└── bar         # Aliases for host bar

First of all, we create a directory to store the aliases.

On ~/.bashrc, we look at that path for a file named as the current hostname. If it doesn’t exist, a file named default is sourced.

We also create a file called base, which may be sourced by each of the other files.

Now let’s dive into that directory.

The base file

In a file that I called base, you place the aliases that you want to be available for every host.

In my case, this include things as simple as alias ll="ls -l" to more complex ones, and it is my biggest file.

I don’t limit this file to which software I have available on all machines. My mindset here is to include everything that doesn’t target any system specifically.

For example, mine has an alias (actually a function) to easily call snapper, although I don’t have it installed on all my machines. It is here because, if someday I install snapper on whatever system, I’ll probably want that alias.

So if something depends on the presence of a software, and not on which host I am, it probably belongs here on base, conditioned to the existence of the binaries on the system. Easy enough.

The host-specific files

You create a file for each system needing their own aliases. This file is named after their hostname.

Here you source base, and then set the additional aliases.

Other thing you might do here is to override some of the base aliases. “Why would I do that?” You might ask.

A example is if one of your systems uses Busybox instead of Coreutils. The former is a smaller version of the tools we are used to in Linux, and, as such, often has different (and less) command-line options. This breaks some of my aliases, such as rm -vI.

I solve it by overriding those aliases in my host-specific file for a “good enough” version of them. I think this makes more sense than removing the affected aliases from base.

Back to your host-specific files, they will be something like this:

# foo
# Aliases for a host called foo

# Source base
. ~/.config/bash_aliases/base

# Specific and overriding aliases for foo
...
...

The default file

Lastly, for the systems in which you don’t need specific configuration, you have a fallback file called default.

Here you do the same thing as in the host-specific files, i.e., source base and then set or override aliases. The difference is that you are targeting the devices that won’t match a specific hostname.

An alternative to write this file is to point those systems directly to base. For me, though, it makes sense to have a layer on top of base, to give me some flexibility.

Conclusion

I came with this approach to my aliases and it’s serving me very well. I don’t have duplicated code, my files are very readable and easily manageable. I also have a fair amount of flexibility. You can see it in action here.

I can think of many ways this solution could be modified and extended to better suit other particular cases. Feel free to adapt it to your needs.



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