November 26th, 2023

Intel Arc A380 as a Plex Media Server Transcoding Accelerator on Linux

Previously, if one wanted hardware accelerated transcoding in one’s Plex Media Server, the options were to either use a Nvidia card, or use an Intel CPU with QuickSync (and a platform that enables the iGPU). With Intel releasing the Arc series of GPUs, a 3rd option emerged. Recently, low profile variants of both the Arc A380 and Arc A310 have become widely available, presenting a low cost, low power, and easy to fit hardware transcoding option. On the software side, not much is needed to get hardware accelerated transcoding working with the Arc A380/A310.

Drivers

First up, you will need the Intel graphics drivers in your kernel. Check your distro’s guides for how to do this (Gentoo has a fairly good wiki entry on this). One item to note, the choice of whether to compile the driver as a module or include it in the kernel depends on your setup. A general rule of thumb that has worked for me: if you use an initramfs, compile the DRM_I915 driver as a module; if you use efistub as your bootloader, build the driver into your kernel and include the firmware into the kernel image.

If you need to include the firmware into the kernel image (building the DRM_I915 driver into the kernel instead of as a module), you will need to install the linux-firmware package before compiling your kernel. Under the firmware loader settings, you’ll need to include the following firmware blobs: the dg2_dmc, dg2_guc, and dg2_huc. As of Linux 6.4.13 these are the versions the i915 driver will want: i915/dg2_dmc_ver2_08.bin i915/dg2_guc_70.bin i915/dg2_huc_gsc.bin

Userland

After rebooting with the new kernel, within the Plex Settings, under the Transcoding section, enabling hardware acceleration should be available. Additionally, the Arc A380/A310 should show up in the Hardware transcoding device dropdown. Make sure both “Use hardware acceleration when available” and “Use hardware-accelerated video encoding” are checked. For the “Hardware transcoding device” option, if you have other GPUs, you may want to select the Arc device so it is targeted. Don’t forget to press the “Save Changes” button.

While Plex is now finding the device, it still may not be able to use it just yet. If libva isn’t installed, Plex will not be able to use the Arc GPU for transcoding. For funtoo users, ensure that your profile has the gfxcard-intel mix-in and then install libva. At this point, hardware transcoding should work. You can double check this by using intel_gpu_top while playing a video. Another method of checking if hardware transcoding is working is through the “Now Playing” section of the Plex dashboard. If you see a (hw) next to the codec and the word Transcode in the video section, hardware transcoding is working.

Note that getting hardware transcoding working with Plex Media Server only required the Intel graphics Linux kernel driver, some firmware blobs, and libva. X server, Wayland, a window manager, and desktop environment were not needed or installed.

-John Havlik

August 23rd, 2020

Notes on LUKS + EFISTUB

Posted by John Havlik in Guides

Running off of an encrypted root filesystem has been one of those things that never seemed to float to the top of the todo list. However, back in December (2018, this article lived in the drafts bin for quite some time), it finally made it to the top of the todo list. At the time, one was preparing the Dell XPS 15 9550 to replace the Ideapad s405 for travel. Encrypting everything seemed prudent for a travel laptop.

As of the writing of this article, LUKS is the standard way of encrypting a filesystem in Linux. Generally, a boot loader is used to kick off an initramfs which loads the basics (need LVM, dm-crypt, and LUKS) and prompts for the passphrase for decrypting the root filesystem. If you’re fine with running a boot loader, most guides will get you going with LUKS quite quickly.

However, running a full boot loader on UEFI systems feels archaic. There is just something about using the kernel’s built-in EFISTUB that feels more elegant. And, this is where things divert from the bog-standard path. Typically, when using the EFISTUB, one does not bother with an initramfs (compile the kernel for you known hardware set and you’re good to go). However, an initramfs is integral to having an encrypted root partition.

initramfs Woes

The first problem started with trying to get a working initramfs. Since one had not used an initramfs with EFISTUB previously, there were a few hurdles to overcome. Initially, one tried to use an external initramfs. However, the 9550 does not allow/pass UEFI parameters nicely, and using the built-in kernel command line to specify an external initrfamfs in the EFI boot partition did not work. So, the initramfs needs to be built into the kernel for the XPS15 9550. This lead to a second problem.

Initially, the initramfs that genkernel builds was tried. Unfortunately, it appears this is (as of late 2018) broken/not-suitable for situations where the initramfs needs to be bundled into the kernel. Luckily, betterinitramfs can be bundled into the kernel.

Naturally, there is one gotcha to keep in mind regarding betterinitramfs. As distributed, betterinitramfs does not populate /dev/disk/by-uuid et al. as it does not provide udev (or eudev). The end result is real root needs to be specified using /dev/BLOCKDEVICENAME rather than using PARTUUID.

Conclusion

While the setup of using EFISTUB with an LUKS encrypted root partition is a little esoteric, it is possible to get working. There are a bunch of UEFI related pitfalls waiting to snare you—different platforms will have a different mix of issues. Then again, all UEFI systems should be able to use the initramfs embedded in the kernel when using the EFISTUB boot loader. Regardless, this path is not advised for those learning about/using LUKS for the first time.

-John Havlik

April 19th, 2019

U2F and Firefox on Funtoo

Posted by John Havlik in General

U2F is pretty neat. It can be used locally on a machine for authentication and for two factor authentication on websites. There are even plugins for using it on WordPress powered websites. At the time this article was written, Firefox does not enable U2F by default. Though, that looks to be changing with Firefox 68.

Enable U2F in Firefox

Enabling U2F in Firefox is fairly straightforward. In the URL bar enter: about:config. Then search for u2f. There should be an entry: security.webauth.u2f, set it to true.

Install pam_u2f

However, simply enabling U2F in Firefox is not enough for a U2F device to work. To get everything working, pam_u2f needs to be installed. On Funtoo, this is quite simple:

emerge -av pam_u2f

After installing pam_u2f, Firefox should now be able to query your U2F key.

March 9th, 2019

Fix Linux Boot Halting on “Run /init as init process”

Posted by John Havlik in Guides

In the process of removing the remaining SandForce controller based SSDs from service, the opportunity to completely refresh the Funtoo install on the XPS 15 9530 was taken. Part of this was to try to figure out why recently sddm would not start until a bit of keyboard mashing occurred (literally pushing the enter key a dozen times in a row caused sddm to start, waiting was simply not enough).

The install was fairly painless—most problems tend to be involve getting the proper device drivers compiled into the kernel. Given there was already a known good kernel config, that was used for the building the kernel on the new install. However, on the first boot off of the new SSD, the boot process halted at:

[2.754164] Freeing unused kernel image memory: 1020K
[2.756196] Write protecting the kernel read-only data: 20480k
[2.758698] Freeing unused kernel image memory: 1980K
[2.760892] Freeing unused kernel image memory: 620K
[2.764980] Run /sbin/init as init process

The init system (OpenRC), for some reason, did not actually kick off. Plugging in a USB device confirmed that the kernel itself was still running. Thus, it was not something simple such as the root device being inaccessible (that causes a kernel panic). But, in this state, the system was not usable (no login prompt).

After a bit of sleuthing and stumbling, a solution was found. The following was added to the kernel config:

CONFIG_DEVTMPFS_MOUNT=y

After rebuilding the kernel and rebooting, the system finally booted completely. Still, this is a little unnerving. This machine never needed this setting before. Additionally, I have not needed this setting on any other machine.

April 15th, 2018

U2F and KDE/SDDM on Funtoo

Posted by John Havlik in Guides

U2F keys, such as the yubico YubiKey are relatively easy and inexpensive way to add two factor authentication to one’s workstation. Adding U2F authentication to local accounts on a linux machine is quite easy. In Gentoo/Funtoo, the pam_u2f ebuild will provide everything you need to get started.