How to get the same Emacs environment on a different computer?

Question

I'm a beginner in Emacs (using it for about 2 weeks now and loving it). As I update and expand my ~/.emacs.d/init.el file, the things that I write in there depend on certain packages that I installed from MELPA using M-x package-install, on .el files that I've written myself, etc.

My question is, should I in the future switch computers for example, what is the best way to seamlessly get the same exact Emacs environment on the new computer as I have now?

Answer 1

The correct solution is to use straight.el, a package manager that I wrote to solve this problem. You can find more details about this in another answer to this question.

This answer, which was written months before I started work on straight.el, previously described a strictly inferior way of achieving a partial solution. This approach is described briefly below; I no longer recommend it.

Even if you don't want to use straight.el, you should at least adopt use-package. (Not that the two are mutually exclusive—I believe the cleanest setup comes from using both.)

---

Start by defining a list of packages in your init-file:

(defvar my-packages
        '(
          aggressive-indent
          avy
           .
           .
           .
          projectile
          undo-tree
          )
  "List of packages to be installed at Emacs startup.")

Then install them automatically:

(require 'cl-lib)
(package-initialize)
(unless (cl-every #'package-installed-p my-packages)
  (dolist (package my-packages)
    (unless (package-installed-p package)
      (package-install package))))

If you keep your init.el file under version control, then syncing it to another machine will result in your packages being installed automatically. Of course, the versions that are installed will be completely different, and your configuration can't be expected to work out of the box as a result. This is a fundamental flaw of package.el, and is one of the reasons why this approach is bad. See again straight.el. Note also that the code outlined above separates your package list from your configuration for those packages, making it harder to keep track of things in your init-file. This is another major disadvantage. See again use-package.

Answer 2

If you use use-package, you can move that file around from computer to computer, and when Emacs starts up, as long as you have internet access, it will pull in the packages and configure them.

First, set up the package library:

(require 'package)
(add-to-list 'package-archives
             '("melpa" . "https://melpa.org/packages/") t)
(package-initialize)

And then bootstrap use-package:

(unless (package-installed-p 'use-package)
  (package-refresh-contents)
  (package-install 'use-package))

(eval-when-compile (require 'use-package))

Now, instead of configuring Emacs and assuming packages are installed, use use-package to both install and configure them. For example, for some of my helm settings:

(use-package helm
  :ensure t
  :bind (("M-x" . helm-M-x)
         ("M-y" . helm-show-kill-ring)
         ("C-x C-f" . helm-find-files)
         ("M-s o" . helm-occur))

  :config
  (helm-mode 1)
  (setq helm-echo-input-in-header-line t))

Answer 3

Next-generation package management with straight.el

After a long and frustrating struggle to use package.el + Quelpa to manage my packages, I bit the bullet and wrote my own package manager. It is intended to completely replace package.el by providing a package management experience that is superior in almost every way.

You can read the very extensive documentation to learn about all of its features, but the most relevant one to this question is that straight.el focuses on perfect reproducibility. This means it should not matter whether you are starting Emacs normally, or starting it on a new machine, and that any local changes are version-controlled and can be reverted to a canonical state. Practically speaking, this is achieved by (1) cloning packages as Git repositories, and providing automated tools for managing their state; (2) using the init-file as the sole source of truth for package management state, with no mutable data stored elsewhere; and (3) using optional version lockfiles to specify exact Git revisions of every package, plus any recipe repositories and straight.el itself.

To get started, insert the bootstrap snippet, which will install and activate straight.el. Then, to ensure that a package is installed, simply place a call to straight-use-package in your init-file:

(straight-use-package 'projectile)

Yes, it's that simple. No dealing with package-refresh-contents or any of that garbage. If you remove this form from your init-file and restart Emacs, Projectile will no longer be loaded (unlike in package.el). This means you do not have to worry about your configuration somehow not working on a new machine because you accidentally depended on undeclared packages.

You can install packages whereever and whenever you would like, throughout your init-file (no need to declare a list of them at a single point). Of course you can also just do

(dolist (package '(ace-jump-mode ... zzz-to-char)) (straight-use-package package))

if you prefer the list. I however recommend that you use use-package to manage your package configuration. First you have to install it:

(straight-use-package 'use-package)

Then, since straight.el has built-in integration with use-package, the following "just works":

(use-package projectile
  :straight t
  :init (projectile-mode 1))

Once you've written your init-file to install the packages it needs, run M-x straight-freeze-versions to save a version lockfile to ~/.emacs.d/straight/versions/default.el. You should keep this file under version control, since it will allow straight.el to check out the correct versions of all your packages, when you first launch Emacs on a new machine. (You can manually revert to the versions specified in the lockfile using M-x straight-thaw-versions.)

To support the idea of machine-local dotfiles that I mentioned in my other answer, straight.el offers a profile system. I still recommend using symlinks for your dotfiles (in this case, init.el, your local init-file if applicable, and the version lockfile if you want to use one).

If you're wondering how straight.el compares with other package managers, check out the extensive comparisons section. But there is lots more documentation on everything else, too.

Answer 4

You can use cask to manage your packages. Use git/github to source control and sync your emacs dotfiles.