A (relatively) deep dive into (zsh) shell login process (without a display manager)

Recently, I have uninstalled my display manager for various reasons. One of the reasons for that was to have a better understanding of my login process. Display managers generally do arbitrary stuff, they have their own way/order of sourcing files, sometimes they skip important files and sometimes they source unnecessary stuff etc. So I thought, using no display manager would result in a simpler login model. Oh boy, I was wrong.

After quite a bit of fiddling around I believe I have a clear mental model of in which order my files gets sourced. Before that, here is a quick summary of some terminology:

[non-]Login shell

It's first thing that is executed when you log in to your system. It generally spawns your DE/WM.

[non-]Interactive shell

It's the shell that you use interactively, shells that you type into.

When you log into a TTY, you get a interactive login shell. When you spawn a new terminal in your DE/WM, you get a non-login interactive shell. When you log in to your DE directly, that is done through a non-interactive login shell. A script that you run is run under a non-login non-interactive shell. These are important because this information will guide you why your PATH variable is not working as intended in some cases and why sometimes it works.

I use zsh as my main shell and I also set it to be my login shell. zsh has a much simpler sourcing hierarchy, I'm not even going to bother myself explaining how bash does it. So here is how it goes:

• First, /etc/zshenv and then ~/.zshev is sourced. This is done no matter what type of shell you are spawning. These files gets sourced every time you are spawning a shell.
  • /etc/zshenv
    • This file might be under /etc/zsh/zshenv instead of /etc/zsh even if man zsh says the exact opposite. Some distributions change this path for zsh and they forgot to update the manual.
    • I don't recommend editing this file unless you really know what you are doing. Just try to utilize files under your home directory, instead of global ones.
  • ~/.zshenv
    • As this file gets sourced every time a new shell spawns, it makes sense to put all the frequently updated stuff here.
    • Also you probably want to set all the environment variables that is frequently used by other programs ($PATH, $PAGER etc.).
    • Do not put any aliases here, aliases are meant to be used within an interactive shell.
• If you are spawning a login shell, /etc/zprofile gets sourced at this point, and then ~/.zprofile. Just to make it clear, these files are only sourced at login and never again (if you somehow spawn a login shell again, of course it will be sourced again).
  • /etc/zprofile
    • Again, this file might be under /etc/zsh/zprofile instead of /etc/zprofile.

    • Most of the distributions have the following line inside the /etc/zprofile file:

      emulate sh -c 'source /etc/profile'
      

      • This file sources /etc/profile file (which automatically gets sourced if you are using sh or bash as your login shell.), which in turn sources files under /etc/profile.d. These files are generally gets installed when you install a program into your system. For example, if you install nix package manager, it also installs /etc/profile.d/nix{,-daemon}.sh files and this files needs to be sourced for nix to work properly. So if your /etc/zprofile or /etc/zsh/zprofile does not contain this line, add it to your ~/.zprofile file.
  • ~/.zprofile
    • This file is a nice place to add stuff that does not change very often, as this file is only sourced at login once.
    • You can also do some long running initializations here, as this file gets sourced only once.

    • Also this is the file that you want to run startx, if you are not using a display manager like me. Here is how I do it:

      # Following automatically calls "startx" when you login on tty1:
      if [[ -z ${DISPLAY} && ${XDG_VTNR} -eq 1 ]]; then
          # Logs can be found in ~/.xorg.log
          exec startx -- -keeptty -nolisten tcp > ~/.xorg.log 2>&1
      fi
      

      • After running startx, it loads ~/.xinitrc file. This is the file that you want to start your window manager and all the other programs that you want to see at startup. An example file might be:

        #!/bin/sh
        
        # The following is essential, you need to source
        # every file under `/etc/X11/xinit/xinitrc.d`.
        if [[ -d /etc/X11/xinit/xinitrc.d ]] ; then
            for f in /etc/X11/xinit/xinitrc.d/?*.sh ; do
                echo "Sourcing $f"
                [[ -x "$f" ]] && . "$f"
            done
            unset f
        fi
        
        sysresources=/etc/X11/xinit/.Xresources
        sysmodmap=/etc/X11/xinit/.Xmodmap
        [[ -f $sysresources ]] && xrdb -merge $sysresources
        [[ -f $sysmodmap ]] && xmodmap $sysmodmap
        
        # Load your keymap and all that jazz
        setxkbmap 'us(intl)'
        xrdb -merge $HOME/.Xresources
        xmodmap $HOME/.Xmodmap
        # Cursor
        xsetroot -cursor_name left_ptr
        # Starting programs like your compositor makes sense here
        picom -b
        # Some other programs related to X
        unclutter &
        redshift &
        # Run your WM, as an example I run bspwm
        exec bspwm
        

• Now, /etc/zshrc (or /etc/zsh/zshrc) and then ~/.zshrc gets sourced, if you are spawning an interactive shell.
  • This is the file that you want to dump all of your aliases, zsh functions that you want to use interactively, your shell theme/plugins etc.
• If you are spawning a login shell, now /etc/zlogin (or /etc/zsh/zlogin) and then ~/.zlogin gets sourced.
  • I don't use this file.
  • Don't use this file if you are already using ~/.zprofile or move all of your ~/.zprofile into this one.
  • Only difference is this file is sourced after ~/.zshrc (if it's sourced at all) and it doesn't make much sense (to me).