Automounting Steam Deck SD Card
Normally (I guess), you need to first enter Desktop Mode, which will automount the SD card. Then you can go back to Game Mode and play your games from the SD card (mostly emulation :) ).
A good thing of the steam deck is that it just runs Linux, so we can use same old tools we are used too.
What we want here is to add the sd card to fstab
Assuming you have SSH access to the deck.
I recommend first automounting it via Desktop mode. It should auto mount to /run/media/deck/{UUID},
you can double check with df -T:
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So mine is using btrfs, pay attention to this, if yours is different the fstab config may change.
Not gonna go into filesystems and whatnot, if you want to be able to access the SD card in a non Linux machine
I recommend exFAT (which works in Mac too) and NTFS (Windows only, although I think you can use a third party tool to have write access in a Mac).
Then, since it’s already mounted, you can peek into /etc/mtab and literally just copy
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Although we need to modify slightly.
Find that partition’s UUID using lsblk -oNAME,UUID
Then edit /etc/fstab, we need to do 2 changes from what we got from /etc/mtab:
- Prefix with
UUID={YOUR_UUID}. This is necessary so that in case the drive name changes (right now it’s/dev/mmcblk0p1), it can be looked up via the UUID. - Add
nofailto the options, this is super important so that it won’t prevent your steam deck to boot in case the SD card can’t be read.
So in my case I added all this to fstab
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Unmount the existing mount point umount /run/media/deck/7408fbbe-276b-4f85-8494-d9549daa4ba0 in my case. You may get a Resource busy, in that case you can technically track all the places that are using that disk using lsof and kill them. Honestly if that happens, I recommend instead to just comment out that line in fstab, then rebooting and immediately going to desktop mode, then you can try to umount again.
Run mount -a everything that’s in fstab.
If it works, reboot and it should be automounting.
Now to make it available in Game Mode (to be able to install Steam games), go to Desktop Mode, open Steam -> Settings -> Storage -> Add Drive, then add your SD card.
It should work now.
bonus: breaking down my fstab config
As I just copied whatever was in /etc/mtab, I didn’t fully understand everything. So let’s look at the docs:
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nofail -> already explained, won’t prevent the boot to fail if the partition can’t be found
rw -> obvious enough, to allow reading and writing
nosuid -> don’t allow having the suid and sgid bits, this is a little complicated, but long story short is a bit that a file can have which will allow anyone to run that as if they were the user that owns the file, the most common case I know is to run as root, like for the sudo binary, since sudo itself allows you to run as root (the owner of the file)
nodev -> not quite sure, I believe it doesn’t allow the filesystem to contain special files, which usually allows talking directly to the device hardware
relatime -> some low level stuff about access time, don’t care really much
ssd -> for what I understand it enables auto detection of ssd and btrfs add some optimizations (https://man.archlinux.org/man/core/btrfs-progs/btrfs.5.en)
space_cache=v2 -> defaults to v2 which is better, not sure why it’s set (https://man.archlinux.org/man/core/btrfs-progs/btrfs.5.en)
subvol=/ -> mounts from a path, not sure it’s useful here
Now looking at all this, it looks like we can simplify it a bit if we use defaults. I found that the kernel has the following defaults rw, suid, dev, exec, auto, nouser, and async. (https://man7.org/linux/man-pages/man5/fstab.5.html), but in reality it may depend on the filesystem, apparently btrfs don’t set anything? But then someone says there are defaults which are different from the kernel’s one.
You know what? I will leave as it is.