Clean shell environment for demos

You are giving demos on your computer, but you have heavily customized .bashrc, .gitconfig, etc. You don't want to have to move these out of the way every time. Linux namespaces to the rescue! clean-shell creates a new mount namespace, which can replace the values of these config files with empty (or minimal) defaults. That shell, and any subprocesses, will experience this clean environment.

Files cleaned by default: .bashrc, ~/.ssh/, and ~/.gitconfig, ~/.gitignore. Furthermore, anything in ~/.clean-shell/ will be replaced (the basename there will have ~/ appended to it) also. Non-existing original files will be ignored (thus, you might make them in the subshell).

Currently only supports Linux, because unshare only works there. But perhaps other operating systems have they own way of doing namespaces? Contributions welcome.

Installation

clean-shell.py is a single-file Python, no installation needed. Requires Python>=3.4.

Dependencies: unshare (pip install --user unshare). This is a thin wrapper around the unshare Linux system call.

Unprivileged users need to be able to use namespaces. You can make this so with sudo bash -c 'echo 1 > /proc/sys/kernel/unprivileged_userns_clone'. I'm currently unclear if this is only disabled in Debian-like Linuxes, or if this is always disabled by default for normal users. If it is disabled by default, this really is much less useful. Expert advice would be welcome here.

Invocation

-v runs in verbose mode (print all files being altered)
--persist will bind-mount the original template files, so that any modifications are persisted across sessions. Perhaps useful for recurring demos where you are defining your own aliases and so on. May have currently-unknown interactions with the different directories.

"Default" files

The first of these values is taken as the replacement value for each file:

~/.clean-shell/BASENAME
DIRNAME/defaults/BASENAME, where DIRNAME is the directory containing clean-shell.py.
A empty file, or an empty directory if the path to be replaced ends in /.

Persistent replacement files

Sometimes, you don't want to completely reset your .bashrc etc. each time you run clean-shell. You can handle that, too.

You can ::: mkdir ~/.csdefaults touch ~/.csdefaults/.bashrc touch ~/.csdefaults/.gitconfig

The files in ~/.csdefault/ are bind-mounted in, and if you use --persist then any changes inside get persisted to this location.

Development and maintenance

Status: Alpha; improvements, including breaking improvements, are welcome.