uprofile: manage multiple profiles for a single linux user

Problem

I work on mutliple contexts (mutliple projects, freelancing, etc). I need to manage multiple profiles (mutliple SSH identites, k8s contexts, git config, etc) and I want to be able to jump between them quickly.

Solutions

Use per-command flags to switch contexts

• Use kubectx for k8s

$ kubectx context1
$ kubectl ...
$ kubectx context2
$ kubectl ...

• Use ssh -i <private key> to use non-default private key
• Use per repo git configuration

Use multiple users

You can create a user for each context and use the default/global configuration files in each user home directory. This works well for completely isolated work. However I often want to share files between all users (like my VIM configuration), which is hard to maintain.

Use uprofile

uprofile allows you to have multiple profiles on the same user, all profiles have their own home directories that is layered on top of the user home directory, so all files that don't need to be edited are shared.

$ uprofile create context1
$ uprofile mount context1
$ uprofile jump context1
(context1) $ git config --global user.email [email protected] # doesn't override original user global config

Principle

uprofile uses fuse-overlayfs to mount profile home directory (similar to docker but without full isolation) and overrides HOME environment variable. Any writes in the profile home directory are not committed to original user home directory, keeping them isolated.

uprofile also uses unshare to jump to the profile context. While not immediately necessary, using unshare allows us to add more complex features later on.

Building

Make sure that fuse-overlayfs and unshare are installed.

$ go build
$ ./uprofile ...

It's prefered to move uprofile binary to ~/.local/bin/ and have ~/.local/bin/ in your PATH environment variable.

Usage

We need a directory /home/$USER.profiles to host all profiles that is accessable by $USER.

$ sudo mkdir /home/$USER.profiles
$ sudo chown $USER: /home/$USER.profiles

Then we can use uprofile to create, mount and jump to a profile

$ uprofile create context1
$ uprofile mount context1
$ uprofile jump context1
(context1) $ ...

a profile can be unmounted later with

$ uprofile umount context1

if the profile is no longer needed, we can delete it (this will delete all the modifications in profile home directory though, so make sure to backup anything you need before that)

$ uprofile delete context1 # context1 must be unmounted first

Advanced

I use monkey patching to overcome some of the applications that don't use/respect HOME env variable. For example, OpenSSH uses getpwuid to retrieve user home directory which we can't easily override. The source for monkey patching is located under patch/ but I won't provide steps on how to use it to ensure that only users who really know what they are doing can use it :)