A Curiosity (USB drive sometimes doesn't mount)

I have one of these triple-connector USB drives:


It’s formatted as: FAT32

.Inserted in Librem 5 (USB-C): Mounts for file transfer.
.Inserted in Linux Mint laptop (USB-A): Mounts for file transfer.
.Inserted in Android phone #1-Nougat (USB-B): Mounts for file transfer.
.Inserted in Android phone #2-Pie (USB-C): Mounts for file transfer.
.Inserted in Android phone #3-/e/Android 10 (USB-C): Does not mount for file transfer…unless I flip it around and re-insert it.

Android phone #3 is running /e/OS, but as I recall, I had the same issue even before installing /e/, although I didn’t realize then that I could just flip the USB drive to make it mount.


EDIT: Using Disks on my laptop, I reformatted the USB drive to “Compatible with modern systems and hard disks > 2TB (GPT)”*…which couldn’t mount on Linux Mint or Android, so I allowed Android to alter it. Now it’s exFAT, and it mounts…but still has to be flipped a certain way on Android.

*Does the “> 2TB” literally mean this format is only for drives “greater than” 2TB in size, or is that just a pointer, or does it mean “up to?”

Fat32 has a max file size of 4 GB. exFAT doesn’t have that restriction. I think that’s all that means (probably more technical details involved).


Thanks. It’s interesting that the drive couldn’t be read by computer or phone until I let Android reformat it again.

I also don’t know why Disks isn’t explicit about what format it’s going to use. Is it just me, or are UIs providing less info and controls than they used to? :neutral_face:

I think this is referring to the partition table, not the file system.

For partition tables, before GPT there was MBR (often referred to as an msdos partition table in the Linux world). MBR can’t handle more than 2TB. It should work fine to use GPT on a disk that is smaller than 2TB.

The main reason not to use GPT would be if the USB drive is sometimes used on a very old computer, and in particular if the USB drive is used to boot said computer. Since the partition table will be interpreted by the BIOS if you are booting the computer, the BIOS may be wildly out of date, or more likely abandoned by the manufacturer and no update is even available - hence or otherwise the computer is unable to boot from a disk that uses a GPT partition table.

Even then, GPT contains compatibility measures so that provided that all code need to start the boot process is located in the first 2TB of the disk, you should get away with booting from a disk that is larger than 2TB and which has a GPT partition table on an old computer with no GPT support in BIOS.

You are probably right but perhaps it is in the name of user-friendliness. Give the above explanation to the average user and eyes will glaze over. The user just wants the damned computer to boot. Right?

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I don’t exactly know the underlying reason, but USB-C is not identical in both orientations. I need to arrange my L5, the cable, and the USB-A to USB-C converter in a certain way before it connects to my laptop.

Thanks for the explanation.

The three options that Disks offers to me when formatting a disk (in addition to erasing or not erasing data) are:

.Compatible with all systems and devices (MBR/DOS)
.Compatible with modern systems and hard disks (> 2TB/GPT)
.No partitioning

I only need this particular drive to work on Linux systems and Android, so I’m confused why the 2nd option wasn’t at first mountable on Linux Mint or Android without letting the Android system “adjust” it…which only took a fraction of a second, by the way, after which it worked fine everywhere.

Maybe Disks isn’t the best application to use for this?

I didn’t realize that. In fact, I thought one of the advantages of USB-C is that it can be inserted any which way.

In any case, I’ve only ever had a problem on Android, as far as I know. But now at least I know the probable solution when a USB-C drive isn’t mounting.

It’s meant to be this way, but it introduces a point of failure which is actually manifesting in practice.

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If you can get back to that situation, we may be able to get to the bottom of it.

You probably need fdisk -l ... output at each stage i.e. as it arrived, after formatting, …

You would need to confirm the drive capacity. It’s 128 GB (as linked in the OP)?

So if I understand correctly, the drive as it arrived could mount on Linux Mint but then you used Linux Mint (Disks) to reformat it and it would no longer mount on Linux Mint. (Then Android did ‘something’ and now the drive mounts on Linux Mint.)

As mentioned above, you need to understand not only what partition table type (MBR v. GPT) you are putting on the drive but also what file system type.

Maybe the support for exFAT under Linux Mint is buggy. Are you running the latest Linux Mint? Do you know what Ubuntu version that pertains to? What kernel version?

I did also read in this forum that the Librem 5 doesn’t ship with exFAT support. Have you installed it? My info is out of date? The drive now doesn’t mount on the Librem 5?

For use exclusively on Linux, I would stick with an ext4 file system. Does Android support ext4?

I always use gparted.

Yes, to all your initial questions. Latest Linux Mint 20.2, Kernel 5.4.0-90. (Ubuntu 20.04 LTS)

I’ve had this drive for several years now, and I don’t recall if it has always been formatted as FAT32 or something else. I may have done that myself years ago, or it may have come that way…not sure. In any case, after Android “adjusted” it, it still mounts on Mint, even reformatted… No problem there. No problem on Android or Librem 5.

But checking again in Disks, I see that it shows:

Partitioning type: W95 FAT32 (LBA)
Contents: exFAT (Version 1.0)

It’s a single partition, btw.

So I don’t know what I’ve done to it, actually.

I’ll try a different application to reformat it to ext4 and see what happens.

EDIT: OK, now I’ve reformatted as ext4, using USB Stick Formatter, which I already had installed… Don’t ask me why I didn’t use that app in the first place… :man_shrugging:

Works everywhere I need it to, with no tinkering by the Android system required. (Although I still have to orient it a certain way when inserting on Android.) And on the L5, there is still the longstanding issue I’ve observed, of its not responding to “Safely Remove Drive” (in Nemo file manager). It does unmount with “Eject,” though. No biggie.

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That’s a fair way off the pace. I’m on Ubuntu 21.10 (kernel 5.13.0-20, today :slight_smile:). I understand that that is the Mint way of doing things. There are always trade-offs.

It sounds as if you have resolved your main problem. Yay!

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