🔊 How I Got Sound Working on My iMac (18,2) After Installing Fedora Linux

When I decided to breathe new life into my aging iMac Retina (model 18,2), Fedora Linux seemed like the perfect fit. Clean interface, strong community, and actively maintained. But one big issue quickly hit me after installation:

No audio output. Not even a hint of sound. Just "dummy output."

This blog walks through how I fixed that and got sound working properly using a custom kernel module for the Cirrus Logic CS8409 chip.

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🔍 What I Learned

• iMac 18,2 uses an unsupported Cirrus Logic CS8409 chip

• The usual Intel HDA tricks (model=mbp101 or imac21) do not work

• Audio devices may show in aplay -l or pactl list sinks, but they won’t function without the right driver

• A custom module exists, but requires compiling

If you're considering Linux on an older iMac, this might help you avoid a full afternoon of confusion. Let’s walk through it.

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🛠️ Step-by-Step Fix for Fedora on iMac 18,2

1. Verify the issue

aplay -l
pactl list short sinks

Check if your only sink is auto_null or HDMI with no analog outputs.

• Purpose: Lists available playback (sound) hardware devices using ALSA (Advanced Linux Sound Architecture).

• Typical output if broken: Only HDMI devices or no sound card at all.

• What you're looking for: No "Analog" device like CS8409/CS42L83 Analog, which means the internal speakers aren't detected.

2. Install Dependencies

Make sure kernel headers and dev tools are available:

sudo dnf groupinstall "Development Tools"
sudo dnf install kernel-devel kernel-headers git

• Purpose for sudo dnf groupinstall "Development Tools"

• Lists all PulseAudio (or PipeWire) output devices ("sinks").

• Typical output if broken: Shows auto_null or HDMI outputs, but no analog-stereo device.

• What you're looking for: Missing analog-stereo means your internal sound card isn’t usable yet.

• Purpose for sudo dnf install kernel-devel kernel-headers git:

  • kernel-devel: Provides headers for compiling kernel modules that match your current kernel version.

  • kernel-headers: Needed for building drivers and modules that hook into the kernel.

  • git: Used to clone the custom driver repository from GitHub.

• Output: Installs these packages or says “already installed.”

3. Clone the Custom Driver

git clone https://github.com/egorenar/snd-hda-codec-cs8409.git
cd snd-hda-codec-cs8409

4. Compile the Module

make

You’ll see warnings, that’s normal.

5. Install the Module

sudo make install

6. Load the Module

sudo modprobe snd-hda-codec-cs8409

7. Verify Audio Devices

aplay -l
pactl list short sinks

You should now see something like:

card 0: PCH [HDA Intel PCH], device 0: CS8409/CS42L83 Analog
...
alsa_output.pci-0000_00_1f.3.analog-stereo

8. Set Default Output (Optional)

Use GNOME Settings → Sound or:

pactl set-default-sink alsa_output.pci-0000_00_1f.3.analog-stereo

9. Reboot and Test

sudo reboot

Play a test sound using:

paplay /usr/share/sounds/freedesktop/stereo/complete.oga

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✅ Final Result

Sound now works flawlessly on Fedora 42 running on my iMac 18,2. Music, YouTube, Bluetooth—all back in business.

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💡 Final Tips

• Backup your working config if you reinstall Fedora later

• This fix works across many distros but may need tweaks for Arch, Ubuntu, etc.

• Bookmark the snd-hda-codec-cs8409 repo!

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🧠 Why This Matters

Many older Macs still have solid hardware. Linux can give them a new purpose, especially for coding, testing, and daily work. But quirks like unsupported audio chips can block progress.

If you’re planning to revive your Mac, especially the 2017 models, just remember: it can be done. Now you know how.