Update: I thought it might be fun to use a 64GB Flash Drive... boy was I
wrong. It took -forever- to install Ubuntu to, and even afterwards the boot time
was so horrendously slow, I think the PS4 crashed trying to boot it. It was a
name brand and the fastest in USB 2 class (from what options I had available).
The 8GB stick I have installed in a timely manner and seems to work perfectly.

Stuff you'll need:
- A PS4 on 1.76
- https://github.com/CTurt/PS4-playground (If you want to self host)
- http://kr105.com/ps4kerneltest/ (These 2 files go on a FAT32 USB stick)
- .iso of Ubuntu 64-bit (Other distros will probably work, too!)
- Oracle's VM software (If you don't want to install from outside your OS)
- Oracle's VM Extension Pack
- USB Stick formatted FAT32 to boot initial Linux kernel (1GB or smaller is fine)
- External HDD or USB Stick 8GB or larger

Caveats:
* Only 1GB LAN is supported currently, 10/100 wont connect
* Only 1080 Resolution is supported currently

Preparing Linux (Ubuntu)

-- You can skip this if you're not a bum and just install it to your external USB device yourself --

Step 1: Install Oracle's VM software AND Extension Pack. Open it up and click on New, give it a name, then choose Linux,
and in the last dropdown box choose Ubuntu (64-bit). The default memory is 768, bump this up to 2048
(2GB) if you have it available just to smooth out the process. On the next screen, choose "Do not add a
virtual hard disk" and then finally Create (accepting the warning about no disk).



Step 2: Click on the settings button and go to Storage. Click on the Optical Drive and choose the
small CD icon, navigate to where you downloaded the Ubuntu .iso and choose that file. You also need to
go to the USB section and set it to USB2 or USB3 if you have it. (If you have a
Quad Core CPU or better, go into System, then Processor and set it to 2 cores)


Step 3: Highlight your VM and click on the Start button. As soon as the black box pops up, click on
the Devices dropdown, go to USB, then choose your USB device. This will detach it from your host OS
and let the VM take control of it for formatting/installation.


Step 4: If you've done everything right so far, you should get to the Ubuntu Installer. Choose
"Install" and the only disk available should be your USB device. Go ahead and go through all the steps,
you can leave almost everything default in the installation. Be aware this will wipe out everything
on your USB device. You may want to check off "Install updates" and "Install third party apps", but
this is optional.


Step 5: Once it boots up, add any files or do any customizations you want, then shut it down
(Top-right corner) and once the VM box closes, remove the USB device and it's ready to go!
If your VM doesn't support USB booting, you'll get an error that the boot device can't be found, just stick it in your PS4, it should be fine.


Booting Linux (Ubuntu)

Step 1: Copy the bzImage and initramfs.cpio.gz to the root of a FAT32 USB stick and plug it into the
PS4. Browse to your self-hosted PS4-Playground or navigate to http://cturt.github.io/PS4-playground/
on your PS4, then choose LOAD! under the Linux Loader section.

Step 2: Once the kernel is booted, you can plug in a USB keyboard and remove the FAT32 device,
substituting it for your USB device with Ubuntu installed. Now, type the following commands:

fdisk -l
(That's an L, for list)

Look for the bootable partition name, it will have a * next to it under the Boot column. It should, in
most cases, be /dev/sdc1/

Step 3: With the bootable partition name handy, type the following (assuming your bootable partition
is /dev/sdb1):

mount /dev/sdb1 newroot/
exec switch_root /newroot/ /newroot/sbin/init

If the switch_root fails, just do it again (up arrow key once)

Step 4: Wait a bit... and voila! Ubuntu running on PS4! Enjoy!



Thanks to fx0day, from whom I stole some stuff from