Arch Linux

bivan

Member

Registered: 2026-02-03

Posts: 62

PC as UMS ?

UMS : USB mass storage.

How to turn a PC as UMS, e.g. for an other PC, a smartphone? So the latter can see the 1st's partition(s)?

Googling "pc as usb mass storage": "not possible"...

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,683

Re: PC as UMS ?

You will need a USB controller capable of running in that mode.  You will probably have the best luck with USB-C.

Try search terms such as "Linux USB Slave" "Linux USB Gadget" or "Linux USB OTG".
I've never tried it on an x86_64 system, but I know it can be done on ARM.  Take, for example, a Raspberry Pi Zero W.  You can power it through the USB.  In that mode, it appears to the host as a USB device operating in a few modes.  One of them is a serial device mode that allows you to connect with a terminal emulator and log into the Rasp-Pi.

As to the specifics, sorry, I don't know.  But it is technically possible with the right hardware.

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seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 76,836

Re: PC as UMS ?

"not possible" w/o some additional HW to turn one host into a periphery, https://en.wikipedia.org/wiki/USB#Limitations (the normal approach is OTG to switch periphery like a tablet into a host for a usb key)

https://en.wikipedia.org/wiki/XY_problem
Why would you even want to do that? You'd still need some daemon to share some paths as virtual disk - at this point just use some regular network protocol?

Edit: also F5…

Last edited by seth (2026-07-11 18:57:35)

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bivan

Member

Registered: 2026-02-03

Posts: 62

Re: PC as UMS ?

F5 ?

According to Gemini (you have a competitor ) it's not possible, it's hardware, e.g. a USB drive has UDC USB Device Controller that a PC lacks.

My goal: my Fairphone 5 has U-Boot, seems able to boot a USB drive with the command usbboot, but: I haven't a USB-C drive & PC - USB cable - smartphone I need to enter this command from the PC, using serial console gadget:

sudo screen /dev/ttyACM0

also the microSD card is not found...
My ultimate goal is to install Arch Linux ARM on the Fairphone 5 the Arch way, without flashing a .img root.

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 76,836

Re: PC as UMS ?

F5: "update the website to see that ewaller already responded in kind"

I haven't a USB-C drive

https://www.amazon.com/usb-c-to-usb-mic … +usb+micro ?
But there's https://www.amazon.de/subtel%C2%AE-Fair … XXLVD?th=1 so the device might require a OTG adapter to run in host mode tbw.
Do you have any USB-C periphery that you could test on the phone just to see whether it runs as host w/o additional hardware?

USB cable - smartphone I need to enter this command from the PC, using serial console gadget:

That sounds like some sideloading where the phone is actually connected as periphery to the PC - make sure to follow the *exact* instructions for the *specific* device (that includes the generation!) with this to avoid bricking it.

Also while there's eg. https://calyxos.org/install/devices/FP5/linux/ I don't see the platform supported by https://archlinuxarm.org - and neither are technically supported here.

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