Avoiding Shell Bloat

There are many things that can be done to customize and extend the behavior of your command shell, and modern Linux distros provide a large number of these activated by default: from handy aliases and colorized output settings to command line completion and new command installation.

But what if you don’t want all those extra settings/extensions? What if you want to exert a finer control of such things yourself? Here is a method of granting such control to you and your users on a per-user, opt-in basis.

The Hook

When a standard Linux command shell starts, it will first execute commands from certain system shell-setup files (/etc/{profile,bashrc} for the bash shell, /etc/csh.{login,cshrc} for the tcsh shell) and then execute commands from the user’s shell-setup files (~/.{profile,bashrc} or ~/.{login,cshrc}) before giving control to the user. [Note: For brevity, I am eliding over details of alternate names for these files and exactly how they are found/selected; see the documentation of the bash and tcsh shells for the full details. –WRS]

Classically, the settings done in these /etc/ files were mostly limited to essentials such as setting the umask value and the command search $PATH. Current linux distros, however, have — presumably in the name of user-friendliness — greatly expanded upon what is done in these shell-setup files (including executing commands from additional files in /etc/profile.d/), providing/activating things such as colorized command output, shell command completion, or even suggesting alternatives to or installation of unrecognized commands:

$ cat /etc/system-release
Rocky Linux release 9.6 (Blue Onyx)
$ catt
bash: catt: command not found...
Similar command is: 'cat'
$ bat
bash: bat: command not found...
Install package 'bat' to provide command 'bat'? [N/y] 

While this may be desired by/for most users, there will be some users that desire a more classical approach. And while it may be possible for these users to undo all the settings and configurations done in the system shell-setup files, it will be simpler to give them a method to avoid having them done at all.

The Un-Hook

The method I have implemented for this on the systems I administer is to add a line to the top of the system shell-setup files to skip their setup actions on the presence of special trigger files in the user’s home directory. Here is the line as added to /etc/csh.login, triggering on the presence of a $HOME/.login.noetc file.

# /etc/csh.login

[ -f $HOME/.login.noetc ] && exit 0 # skip the rest if unwanted --WRS

[[ ... rest of file as distributed ... ]]

Similar lines are added to /etc/{csh.cshrc,profile,bashrc}, triggering on $HOME/.{cshrc,profile,bashrc}.noetc respectively.

As these trigger files do not normally occur w/out the user explicitly creatings them, and the system shell-setup files behave as distributed w/out their presence, these changes should not affect ’normal’ users in any way.

If a (presumably experienced) user does wish to forgo the system setup files for their shell, they merely have to create the appropriate trigger-file(s) in their home directory, and all such setup will then be omitted. In opting out of these setup actions, however, the onus of making sure that any required setup is completed (e.g. umask, $PATH, etc.) falls on the user, hence the presumption that this will only be attemped by experienced users.