Benoit J - My mostly tech blog

Display Manager With Autologin - How I Use Linux Desktop at Work - Part4

2020-06-12

Part 4 of the series How I use Linux desktop at work where I describe how I’m building a new Vagrant configuration to use for coding on Windows Host systems.

This post describes the learning process to setup LightDM with autologin.

As with previous posts, I will go over the research and manual implementation first, then go over how to automate it.

In part 3, I described how I automated the build of the VirtualBox guest additions using vagrant. Part 4 will improve our current box by swapping the display manager to LightDM and setup autologin.

Previous posts:

  1. part1 - Basic setup
  2. part2 - X, and WM
  3. part3 - VirtualBox guest additions

In the post, I’ll cover:

  1. Rationale
  2. Installing lightDM, a greeter
  3. Configure autologin
  4. Automating the whole thing
  5. Thoughts and next steps

Steps 1-4 are describing the manual process while step 5 describe how I automated this in the Vagrantfile.

Note: You can find the sources created during this post in my github devbox-arch repository.

Rationale

I want to setup autologin since I want to get in the guest linux box ASAP without unecessary login.

I only want to do this on a vagrant box under certain conditions:

  1. This vagrant box has a virtual NAT network enabled and no port forwarded except ssh using ssh keys setup by vagrant
  2. This box is secured by my host OS credentials. I cannot get in this box without unlocking my Host desktop.

Installing lightDM, a greeter, and XSession

I really like the quality, somewhat simplicity and features that lightDM gives.

The setup I usually put in place with lightDM:

  1. lightDM itself
  2. the gtk greeter. There are better greeter, but this one is simple, available everywhere
  3. a xsession that starts my ~/.xinitrc

In arch, this means installing lightdm, lightdm-gtk-greeter, and xinit-xsession (AUR)

For the first two, its simple:

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pacman -S lightdm lightdm-gtk-greeter

xinit-xsession is part of AUR, so it’s a bit more involved as you have to build it from source.

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# some required tools
pacman -S git fakeroot

# now clone the AUR git repository
git clone https://aur.archlinux.org/xinit-xsession.git
cd xinit-xsession
makepkg -sic --noconfirm

Now time to enable lightdm:

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systemctl enable lightdm
systemctl start lightdm

You’ll now see the lightdm greeter with the vagrant user pre-selected.

If you want to login, the password is vagrant.

Note that you can select xinitrc as a session in the session selection at the top right of the screen.

Configure autologin

Autoconfig is configured in lightDM main configuration /etc/lightdm/lightdm.conf.

You must set the following two properties to get autologin with xinit session enabled:

[seat:*]
autologin-user=vagrant
autologin-session=xinitrc

Note: you have to uncomment the two properties under the existing seat configuration.

You can restart lightdm to see it in action:

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systemctl restart lightdm

You also need to add the autologin group and add user vagrant to this group:

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groupadd -r autologin
usermod -a -G autologin vagrant

Automating the whole thing

All changes were made to the 2-core.sh script.

The interesting part is how to install xinit-xsession and then setup lightdm for autologin.

Installing xinit-xsession using AUR comes to one command:

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cd /tmp
    && sudo -u vagrant git clone https://aur.archlinux.org/xinit-xsession.git && \
    cd xinit-xsession && \
    sudo -u vagrant git checkout 7cae213844b && \
    sudo -u vagrant makepkg -sic --noconfirm

Note: makepkg needs to run as a regular user, so you need to clone, and call makepkg using vagrant.

Enabling autologin can be done using sed:

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sed -i -e 's/# *autologin-user=.*/autologin-user=vagrant/' /etc/lightdm/lightdm.conf
sed -i -e 's/# *autologin-session=.*/autologin-session=xinitrc/' /etc/lightdm/lightdm.conf

The sed’s -i option enables in-place editing which change the file specified.

The last part, creating a .xinitrc that calls openbox:

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cat <<EOT > ~vagrant/.xinitrc
#!/bin/bash
exec /usr/bin/openbox
EOT

chown vagrant:vagrant ~vagrant/.xinitrc
chmod +x ~vagrant/.xinitrc

Here, the file is created as root, and then ownership is transferred to the vagrant user.

Thoughts and next steps

I hope I am able to demonstrate how easy it is to provision a Linux development VM using vagrant and some unix scripts.

The hardest part is done, getting a foundation to install development tools and configuration.

In next post, I’ll configure this VM using chezmoi. This will allow me to bring my dotfiles and installation scripts.

When I started this blog, I was hoping it would be useful to others. Now I see that it may be as useful to me. It makes me thinks of my goals, think about improving, it makes me learn.

I hope this series inspires people to shape tools to meet their needs.

This is day 6 of my #100DaysToOffload. You can read more about the challenge here: https://100daystooffload.com.