Raspberry Pi 3 - Browser Client

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This is a guide for setting up a RAM based Alpine which is able to run X, and firefox. This tutorial will go through setting up auto login, and starting X on boot without user interaction, useful as a kiosk or for digital signage.

Tested as of 05/2020 - RPI 3

12/2020 - x86

04/2021 - RPI 4

Overview

This guide uses the following:

  • aarch64 img (though this guide is also x86-compatible)
  • Raspberry Pi3
  • community repo.

It is based on this guide: Raspberry_Pi. Due to the dependencies required to run X and Firefox, after this tutorial is complete there is very little RAM disk space for the user to operate in. (about 30MB in v3.11). The 2GB RPI 4 has 1GB of ram available without adjusting /boot/config.txt. 1GB may be enough for most needs.

aarch64 is used because firefox-esr is in the community repo. armhf (as of v3.11) does not have firefox prepackaged in the base or community repo.

See https://pkgs.alpinelinux.org/packages?name=*firefox*&branch=v3.11&arch=aarch64

Note: the aarch64 build is not compatible with all Raspberry Pi models. See Raspberry Pi.

Steps

Base Install

These steps are duplicated from the Raspberry_Pi page.

Use fdisk or gdisk to format the SD card. The first partition must be a bootable, FAT filesystem. e.g.:

Command (m for help): p
Disk /dev/sdb: 59.5 GiB, 63864569856 bytes, 124735488 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Device     Boot Start      End  Sectors Size Id Type
/dev/sdb1  *     2048 62916607 62914560  30G  b W95 FAT32
mkdosfs -F 32 /dev/sdX1

untar onto mounted disk

mount /dev/sdX1 /mnt/folder
tar xvf archive.tar -C /mnt/folder/.

If you plan to increase available RAM (e.g. for RPI4 with 2 or 4GB) or change other config settings, do so in usercfg.txt now.

Again, duplicating the Raspberry Pi page

   Insert the SD card into the Raspberry Pi and turn it on
   Log in to Alpine as root. Leave the password empty.
   Type setup-alpine, hit enter.
   Once the installation is complete, commit the changes by typing lbu commit -d

Things to keep in mind:

  • There is no need to make multiple partitions (e.g. on an sdcard). One partition that occupies the entire storage medium will suffice in diskless / sys mode.
  • For the setup-alpine install, most of the choices will be the defaults. Particularly when prompted with "No disks available, try boot media /mmcblk0p1". Select the default [n]. If you make a mistake during the install, you can always reimage and start over.

Saving space: busybox instead of chronyd, dropbear instead of openssh

After setup, make sure dropbear is installed

apk add dropbear

Start it:

rc-service dropbear start

Add it to the default runlevel:

rc-update add dropbear

If you need an accurate clock, enable software/ntp here. (this step is optional)

rc-update add swclock boot # enable the software clock 
rc-update del hwclock boot # disable the hardware clock
setup-ntp

Browser Client Install

Enable community repo (/etc/apk/repositories) (uncomment community)

nano /etc/apk/repositories
apk update

install the firefox and X dependencies:

apk add libx11-dev libxft-dev libxinerama-dev adwaita-gtk2-theme adwaita-icon-theme ttf-dejavu

Note: the fonts/icon theme is required for FF to display correctly. Without it, firefox will load, but text will not render on the browser menus.

the amount of RAM tmp fs available can be viewed while installing with: watch df -h

install firefox

apk add firefox-esr

install X

setup-xorg-base

The RPI also requires for X:

apk add xf86-video-fbdev

note: this command can vary if you are using x86. For example, I installed no xf86-video... drivers, and had a libEGL.so missing library error on Xorg that was resolved with "apk search libEGL.so" which pointed to mesa-egl. Note: apk search is case sensitive.

At this point, we have about 421MB of RAM used (if NTP was not set up).

Filesystem                Size      Used Available Use% Mounted on
devtmpfs                 10.0M         0     10.0M   0% /dev
shm                     457.9M         0    457.9M   0% /dev/shm
/dev/mmcblk0p1           30.0G    259.4M     29.7G   1% /media/mmcblk0p1
tmpfs                   457.9M    420.0M     37.9M  92% /
tmpfs                    91.6M    188.0K     91.4M   0% /run
/dev/loop0               24.9M     24.9M         0 100% /.modloop
lbu_commit -d

AutoLogin, Startx automatically on Boot

At this point, you should be able to login as root, and run startx manually. Now we'll add configuration files to enable that without user interaction.

/root/ doesn't save any files, so it's necessary to edit files in /etc/ and run lbu_commit -d after all changes. First let's add a file that we'll call firefox. lbu_commit is alpine local backup. If you want to save folders other than /etc see:https://wiki.alpinelinux.org/wiki/Alpine_local_backup#Include_special_files.2Ffolders_to_the_apkovl also see: /etc/apk/protected_paths.d/lbu.list

create a file named /etc/startup.sh:

#!/bin/ash
firefox http://somewebsite.com

!!!NOTE: This is ash, not bash. By default, alpine ships with the ash shell. Bash is available in the repositories.

We have to edit xinitrc, and the profile configs. Normally, this would be done in the user's directory, but here we will use the globals for simplicity.

mv /etc/X11/xinit/xinitrc /etc/X11/xinit/xinitrc_BAK
nano /etc/X11/xinit/xinitrc

In this file, insert:

/etc/startup.sh

At the end of /etc/profile (leave the existing file) append

startx

Remember to run lbu_commit -d
For autologin, alpine uses busybox, which has an alias to /sbin/getty as well as /bin/login. It's possible to navigate to /sbin/ or /bin/ and run /sbin/getty -h to see what settings are available. To have root auto login at boot, review the existing inittab and edit as needed according to the config below:

# Set up a couple of gettys
#tty1::respawn:/sbin/getty 38400 tty1
tty2::respawn:/sbin/getty 38400 tty2
tty3::respawn:/sbin/getty 38400 tty3
tty4::respawn:/sbin/getty 38400 tty4
tty5::respawn:/sbin/getty 38400 tty5
tty6::respawn:/sbin/getty 38400 tty6

tty1::respawn:/bin/login -f root

Disable Screensaver, and refresh webpage (optional)

As a kiosk, a Raspberry Pi needs to have the screensaver (DPMS) disabled. My particular application (video streams) required a refresh occasionally. These were managed with xorg.conf, xdotool, and crontab respectively.

Contents of /etc/X11/xorg.conf

Section "Extensions" Option "DPMS" "Disable" EndSection

# apk add xdotool

# crontab -u root -e 
* * * * * DISPLAY=:0 /usr/bin/xdotool key F5

Note: xset is not an option here as it's not included by default. It can be installed from the repositories, if needed.
That's it. Reboot and the RPI should boot into firefox without user intervention. At this point, you have a functioning minimal OS booting from RAM, with firefox, and ~30MB of available space for further configuration.

Digital Signage

It's common to use GNULinux and x86/RPIs for digital signage. A quick glance at https://elinux.org/RPi_Projects/Digital_Signage will show a number of options. Why would you use this guide for digital signage vs. those pre-built projects?

  1. Alpine runs from RAM, which increases the lifetime of the storage (flash / hdd).
  2. There is no requirement to use 'cloud' services, or an internet connection.
  3. You have full control over the build and design (all kiosk build steps are documented & have a small learning curve, compared to some of the more complex projects mentioned above).
  4. Free software. No recurring costs (outside of optional maintenance).
  5. No ties to external infrastructure / frameworks. Full freedom.

In this addition to the guide above, we'll install Chromium, which seems to be the defacto standard. However, you could use any X-Window application. Here we'll also run a web server with PHP, which hosts the resources we want to display on the sign. Make sure community apk is enabled in /etc/apk/repositories

apk add chromium

In /etc/startup.sh add chromium instead of firefox:

 chromium-browser --home-page http://127.0.0.1/resource --no-sandbox --window-size=1920,1280 --start-fullscreen --test-type

Note: this is a potentially insecure setup. Users are advised to add a user, and remove the --no-sandbox tag. The following tags are used: --home-page will start us on a given URL. --no-sandbox will allow root to run chromium. --window-size will give us the resolution we want, and start-fullscreen will ensure the browser occupies the entire screen.

If you deploy the device on a TV, and you're unsure what resolution it is, you can access the resolution from the terminal (not in X), by using

xrandr -d :0

For example, I built my device on a computer monitor that was 1920x1280, but when I deployed, the TV was 1920x1080. Since we run chromium straight on X, without any WM, it's necessary to query xrandr from the console. If desired, you could install DWM and hide the bar, obtaining access to a terminal accessible via keyboard shortcut configured in dwm's config.h, But a WM is not required.

Make sure to run lbu_commit -d, in order to save any changes as needed in the apkvol on the SD or HDD storage.

Install Apache/PHP

See Apache.

Install xset to disable screensaver

apk add xset
xset q
xset s off

Hide Scrollbars of Browser

This can be done with CSS.

body {
  overflow: hidden; /* Hide scrollbars */
}

Tips/Troubleshooting

Why was this setup used? Why not Awesome, or dwm?

I ran through a few different setups of Alpine on the RPi, and found that (dwm | awesome) and Firefox required too many dependencies to run on an RPI3 with 512MB in /tmp (running in RAM). Other browsers that used fewer dependencies were unstable (the application was viewing video streams). Running firefox direct on X fit in the available space, and was stable. This is one of the reasons aarch64 was used, instead of armhf. With Alpine, by default the 2GB RPI4 has 1GB of RAM available (for storage), and doesn't have this limitation. It should be possible to get more RAM via /boot/config.txt

If your application doesn't require media (e.g. a static webpage) you may be able to run other browsers on the RPi, such as midori, falkon, or surf, without stability issues.

It is possible that VLC or a GTK/QT app would also fit into the limited space on the RPI 3. That was not tested.

Width & height of firefox doesn't fit the monitor

Firefox can be called with -height and -width flags, e.g.

firefox -width 480 -height 640 somewebsite.com

Periodic Firefox Crashes on RPI3 due to Low Memory

With the RPI3, I found firefox would crash consistently after watching video for a couple of days. On the server I saw notices of memory running out. This may have been a memory leak. With the small amount of RAM available, Firefox would crash, leaving the screen blank.

The solution was to setup a nightly reboot of the system via cron. The system has been stable since. However, if I were to do this again, I would use an RPi4 with >1GB ram which may eliminate the need for a nightly reboot.


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