Unable to set relative line number as a default

Question

I am trying to setup Emacs to have relative line numbering enabled by default via this plugin.

According to the readme file

Relative line numbering should already be enabled by default (by installing this package), following linum-on

I have included (linum-on) in my .emacs file but it doesn't work. M-x linum-relative-mode works, but I have to do it every time.

My full .emacs file at present is below:

(if (display-graphic-p)
    (progn
      (setq initial-frame-alist
            '((tool-bar-lines . 0)
              (width . 106)
              (height . 60)))
      (setq default-frame-alist
            '((tool-bar-lines . 0)
              (width . 106)
              (height . 60))))
  (progn
    (setq initial-frame-alist '((tool-bar-lines . 0)))
    (setq default-frame-alist '((tool-bar-lines . 0)))))
(setq package-list
      '(use-package evil helm js2-mode monokai-theme linum-relative org
        powerline rainbow-delimiters projectile helm-projectile flycheck))
(require 'package)
(setq package-archives '(("melpa"        . "http://melpa.org/packages/")
                         ("MELPA stable" . "https://stable.melpa.org/packages/")
                         ("gnu"          . "http://elpa.gnu.org/packages/")
                         ("marmalade"    . "http://marmalade-repo.org/packages/")))
(package-initialize)
(unless package-archive-contents (package-refresh-contents))
(dolist (package package-list)
  (unless (package-installed-p package) (package-install package))) 
(setq evil-want-C-u-scroll t)
(require 'evil)
(evil-mode 1)

;; Use `display-line-number-mode` as linum-mode's backend for smooth performance
(setq linum-relative-backend 'display-line-numbers-mode)
(require 'linum-relative)
(linum-on)
(require 'helm-config)
(set-face-attribute 'default nil :height 140)
(load-theme 'monokai t)
(global-set-key (kbd "M-x") 'helm-M-x)
(global-set-key (kbd "C-x C-f") 'helm-find-files)
(menu-bar-mode -1)
(tool-bar-mode -1)
(scroll-bar-mode -1)
(require 'powerline)
(powerline-default-theme)
(add-hook 'prog-mode-hook #'rainbow-delimiters-mode)
(linum-relative-mode)
(custom-set-variables
 ;; custom-set-variables was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 '(package-selected-packages
   (quote
    (flycheck rainbow-delimiters powerline linum-relative doom-themes moe-theme cyberpunk-theme monokai-theme helm evil))))
(custom-set-faces
 ;; custom-set-faces was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 )

Answer 1

linum-on acts on the current buffer only. That is not what you want in an init file.

You actually want the action of global-linum-mode which switches on linum-mode in all buffers where it is appropriate.

So replace (linum-on) with (global-linum-mode). You can also directly use

(linum-relative-global-mode)

instead.