Using XFCE.
I plug a no name USB stick into a slot. My file manager PCManFM does not see it. I try a different slot to make sure. No difference. I invoke “fdisk -l” and nothing shows. Then I plug it into a Windows 10 box and it’s recognized and can be formatted to FAT32. Now PCManFM recognizes it.
Can someone explain what is happening?
As usual, people need to see things. Just not “I invoke “fdisk -l” and nothing shows”, but copy/paste of the statement and the output between CODE tags in your post.
Now I can understand you did not copy it during your effort to find out what is going on, but the result is that we have nothing and that probably you can not re-create the problem.
Alas.
As requested.
ion # fdisk -lDisk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: TOSHIBA DT01ACA1
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x819a5ed7
Device Boot Start End Sectors Size Id Type
/dev/sda1 2048 4196351 4194304 2G 83 Linux
/dev/sda2 4196352 67110414 62914063 30G 83 Linux
/dev/sda3 * 67110912 130025471 62914560 30G 83 Linux
/dev/sda4 130027518 1953525167 1823497650 869.5G 5 Extended
/dev/sda5 130027520 150999039 20971520 10G 83 Linux
/dev/sda6 151001088 171972607 20971520 10G 83 Linux
/dev/sda7 171974656 1953525167 1781550512 849.5G 83 Linux
Partition 4 does not start on physical sector boundary.
localhost:/home/ion #
I am confused now.
I thought you told the problem is gone (by creating an FAT32 file system on it).
Is that correct or not?
Is the device connected to the system at the moment you made that fdisk -l or not?
The problem is now gone after it was formatted in Windows. Before that openSUSE never recognized it as my post of fdisk showed. Of course the stick was inserted before I invoked the fdisk command. Perhaps I should repeat the sequence of events.
ion # fdisk -lDisk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: TOSHIBA DT01ACA1
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x819a5ed7
Device Boot Start End Sectors Size Id Type
/dev/sda1 2048 4196351 4194304 2G 83 Linux
/dev/sda2 4196352 67110414 62914063 30G 83 Linux
/dev/sda3 * 67110912 130025471 62914560 30G 83 Linux
/dev/sda4 130027518 1953525167 1823497650 869.5G 5 Extended
/dev/sda5 130027520 150999039 20971520 10G 83 Linux
/dev/sda6 151001088 171972607 20971520 10G 83 Linux
/dev/sda7 171974656 1953525167 1781550512 849.5G 83 Linux
Partition 4 does not start on physical sector boundary.
localhost:/home/ion #
My question is why did fdisk not recognize it when Windows did?
OK, thus you kept that fdisk -l somwehere topost it later.
Then we must conclude that the system did not recognize the device (let alone that some file manager on some user’s desktop saw files on it).
But that does not bring us much further, because, as I explained earlier, we do not have the situation as it was before. Thus we can not now connect the device and see what the system tells us.
Well of course you could, as another secret, have done that also and kept it somewhere to produce it when I ask for it 
Very true. It’s too late now. But since the stick came from a friend, if I were to get another with the same problem, how would I go about diagnosing the problem? What command?
I normally use (as root)
dmesg -w
(but there may be a more “modern” command).
It will show you some logging an stop there. Enter the device and it will show new lines. Copy/paste the new ones then.
Stop the dmesg with Ctrl-C.
(but there may be a more “modern” command).
journalctl -f
as root, after that command put in the stick and post all new entries here.
Too late now, it’s been formatted under Windows. But perhaps I can get hold of another like it. It will take some time as I am under quarantine.
journalctl -f
is a good indicator for USB-Hardware…
Made a note of that. I really have to get up-to-date myself 
Either works satisfactorily though. The journalctl command needs to be run with sudo, (unless the user is a member of the ‘systemd-journal’ group IIRC).
If USB stick is not formatted then there is nothing to mount.
Format it then use it.
For 8 GB exFAT is preferable.
This thread is already a bit old, but when I remember correct, it was not only the silly Dolphin that did not see any file system (because there was none), but also fdisk -l did not show the device. It is that last point that still wonders me.
sometimes the usb bus randomly braks for drives for no reasin and formatting can helpp or the drive is currupt
—Citaat (Origineel door ionmich)—
if I were to get another with the same problem, how would I go about diagnosing the problem? What command?
—Einde Citaat—
The magic command is – with the user “root” – “lsblk --fs” …
“fdisk -l /dev/sd?”
“gpart /dev/sd?”
“gdisk -l /dev/sd?”
Once you’ve worked out which device the USB stick is, check if it has a Partition – if it doesn’t you’ll have to create an MBR (DOS) Partition:
“fdisk /dev/sd?”
With the menu – “m” for help and so on – you’ll probably need either a “W95 FAT32” partition or, a “HPFS/NTFS/exFAT” partition.
Once there’s a MBR partition on the USB disk, you’ll have to format it –
If you have the “exfat-utils” RPM package installed from the openSUSE Repositories then, you can also format larger USB sticks – “mkexfatfs /dev/sd?1”
Why PCManFM in xfce?
Thunar is good in recognizing removable usb etc… even iphone.