RetroArch core updater for Steam on Linux (Dolphin, PCSX2, Azahar)

update_cores.sh

#!/bin/bash
# update_cores.sh — RetroArch nightly core updater for Steam (Linux)
#
# Updates the following libretro cores from buildbot.libretro.com nightly builds:
#   - Dolphin  (GameCube / Wii)
#   - PCSX2    (PlayStation 2)
#   - Azahar   (Nintendo 3DS)
#
# Also downloads matching .info files and required system files.
#
# Usage:
#   chmod +x update_cores.sh
#   ./update_cores.sh
#
# Requirements:
#   - RetroArch installed via Steam (default path assumed)
#   - wget, unzip
#
# Notes:
#   - PS2 BIOS not included — place manually in: ~/.steam/steam/steamapps/common/RetroArch/system/pcsx2/bios/
#   - 3DS BIOS/keys optional — place in: ~/.steam/steam/steamapps/common/RetroArch/system/

set -e

RA="$HOME/.steam/steam/steamapps/common/RetroArch"
BUILDBOT="https://buildbot.libretro.com/nightly/linux/x86_64/latest"
ASSETS="https://buildbot.libretro.com/assets"
TMP=$(mktemp -d)

trap 'rm -rf "$TMP"' EXIT

CORES=(
    dolphin_libretro.so.zip
    pcsx2_libretro.so.zip
    azahar_libretro.so.zip
)

echo "==> Downloading cores..."
for core in "${CORES[@]}"; do
    echo "  $core"
    wget -q --show-progress -P "$TMP" "$BUILDBOT/$core"
    unzip -oq "$TMP/$core" -d "$RA/cores/"
done

echo "==> Downloading info files..."
wget -q --show-progress -O "$TMP/info.zip" "$ASSETS/frontend/info.zip"
unzip -oq "$TMP/info.zip" dolphin_libretro.info -d "$RA/cores/"
unzip -oq "$TMP/info.zip" pcsx2_libretro.info   -d "$RA/cores/"
unzip -oq "$TMP/info.zip" azahar_libretro.info  -d "$RA/cores/"

echo "==> Downloading system files..."

mkdir -p "$RA/system/dolphin-emu"
wget -q --show-progress -O "$TMP/Dolphin.zip" "$ASSETS/system/Dolphin.zip"
unzip -oq "$TMP/Dolphin.zip" -d "$RA/system/dolphin-emu/"

wget -q --show-progress -O "$TMP/LRPS2.zip" "$ASSETS/system/LRPS2.zip"
unzip -oq "$TMP/LRPS2.zip" -d "$RA/system/"

echo "==> Done."
echo "    PS2 BIOS → $RA/system/pcsx2/bios/"
echo "    3DS BIOS → $RA/system/ (optional)"

spent way too long trying to get standalone RetroArch running through Steam while keeping cloud saves. tried basically everything:

• replacing the binary with a wrapper → Steam runs inside a pressure-vessel container, /usr/bin doesn't exist in there
• STEAM_COMPAT_MOUNTS=/usr to expose host fs → container explicitly blocks /usr
• /run/host/usr/bin/retroarch since host is mounted there → binary ran but missing libpulsecommon and other libs not in the container runtime
• STEAM_RUNTIME=0 to skip the container → still sandboxed somehow
• copying standalone libs into the game dir → should work in theory but was too fiddly
• AppImage: extracted and replaced the whole Steam RA directory → no retroarch.sh so Steam couldn't launch it, also broke mist (the Steam↔RA bridge)
• custom retroarch.sh calling AppRun from the AppImage → ran, but fonts broken because config pointed to /usr/share/libretro/assets/ which doesn't exist in the container. fixed that, fonts worked standalone, broken again from Steam because container resolves paths differently
• also couldn't resize the window at all - gl driver doesn't work properly on Wayland

ended up just going back to stock Steam RetroArch and manually dropping the missing cores from buildbot.libretro.com into cores/. took 5 minutes. hence this script.