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5K iMac 2019: CachyOS Install Notes

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Disclaimer: This is not an exhaustive guide, but my notes on how I setup CachyOS on my 2019 5K iMac.

My Setup:

  • iMac (Retina 5K, 27-inch, 2019) - iMac 19,1 already running MacOS.
  • Battle scars of prior Linux installs, like a residual GRUB setup.
  • Fusion Drive is replaced with an Samsung 870 EVO SSD.
  • Stock 8GB of ram updated to 16GB.

Important:

  • Have your lightening cable hooked up to the mac and the apple keyboard.

Status Quo

I’m not going back, It’s stable. Much more performant for my development workflows and I can play games! Proton via Steam!

fastfetch
Image 1: fastfetch

  • ✅ Wi-Fi
  • ✅ Bluetooth (Audio not tested)
  • ✅ 5K resolution (Check Side Quest)
  • ✅ Audio Out (Speakers sounds meh, RIP Apple DSP, possible future improvement)
  • ❔ Microphone (My mic was already cooked after a botched SSD install)
  • ✅ Ethernet
  • ✅ Dimming backlight
  • ✅ Fan control (yeah, you need to do that yourself)
  • ❌ Suspend (I’m a sicko who does not turn off computers)

Guide

I’m not going to regurgitate anything as there is an excellent guide by Misternoli, which only inspired me to try this.

Link: iMac 19,1 Installation Guide

Deviations From Guide:

  • Used the t2Linux firmware.sh option to copy drivers over to the EFI partition, but keep a copy too.
  • Used the Gnome desktop environment, as opposed to KDE which is selected by default.
  • Brightness customization was not needed, it worked for me by default.
  • Forked the fancontrol solution with some customization.

Battles

Problems run into and solutions.

Battle A: Cannot Shrink & Partition APFS

  • My drive is encrypted and has errors.
  • Booted into Recovery (Restart and hold CMD+R)
  • Go to disk utility
  • Unmount all volumes under container (which is under the internal drive)
  • Important, go volume by volume and run first aid (running first aid on the whole disk is not enough)
  • Then pick the Drive and hit partition - Create a new partition not volume, pick MS-DOS.

Battle B: Cannot boot into USB drive

  • Follow preparation instructions on CachyOS docs.
  • Reboot iMac and hold Option key.
  • Plug in USB drive (it detects hot plugging)
  • Pick the EFI boot (orange icon)

Battle C: Refusing to install to a small EFI partition

  • Installer won’t let you proceed as EFI partition is small. Trick the installer!
  • Edit the installer config.
    • Exit installer
    • Open terminal
    • Edit Config:sudo nano /etc/calamares/modules/partition.conf
    • change efiSystemPartitionSize occurrences to 100M.
    • Make Config Read Only: sudo chattr +i /etc/calamares/modules/partition.conf.
    • Start Installer.

Credits: Fellow Reddit User

Side-quests

Things done to made me want to stay on this setup.

Quest A: Fancontrol

I customized the guides fan control script to make it customizable via config file and made some tweaks,

Git Repo: kaveenr/imac5k-fancontrol

Quest B: 5K Resolution

The default amdgpu driver only outputs in 4K, which is just sad. I found some prior attempts for other operating systems and adapted it to CachyOS.

Git Repo: kaveenr/imac5k-cachyos

Please read the disclaimer, this was an LLM assisted port and I can’t assure (yet) that this auto setup will work for all.