Gnome, nautilus copy files to USB stops at 100% or near

Question

I had similar issues before but i don't remember how i solved it.

When i try to copy something to USB stick, with FAT, it stops near the end, sometimes at 100%. And of course, when i transfer the memory stick somewhere else, it doesn't contain complete file. (file is a movie!)

I tried to mount device with mount -o flush, but i get same issue.

Also, i did format the USB stick with new FAT partition...

Any idea what cold i do?

p.s. I believe it's not related to OS, which is Debian, and i believe that coping from SSD drive doesn't make it stuck.

Answer 1

The reason it happens that way is that the program says "write this data" and the linux kernel copies it into a memory buffer that is queued to go to disk, and then says "ok, done". So the program thinks it has copied everything. Then the program closes the file, but suddenly the kernel makes it wait while that buffer is pushed out to disk.

So, unfortunately the program can't tell you how long it will take to flush the buffer because it doesn't know.

If you want to try some power-user tricks, you can reduce the size of the buffer that Linux uses by setting the kernel parameter vm.dirty_bytes to something like 15000000 (15 MB). This means the application can't get more than 15MB ahead of its actual progress. (You can change kernel parameters on the fly with sudo sysctl vm.dirty_bytes=15000000 but making them stay across a reboot requires changing a config file like /etc/sysctl.conf which might be specific to your distro.)

A side effect is that your computer might have lower data-writing throughput with this setting, but on the whole, I find it helpful to see that a program is running a long time while it writes lots of data vs. the confusion of having a program appear to be done with its job but the system lagging badly as the kernel does the actual work. Setting dirty_bytes to a reasonably small value can also help prevent your system from becoming unresponsive when you're low on free memory and run a program that suddenly writes lots of data.

But, don't set it too small! I use 15MB as a rough estimate that the kernel can flush the buffer to a normal hard drive in 1/4 of a second or less. It keeps my system from feeling "laggy".

Answer 2

Late to the party, but a workaround I use to copy big files to USB stick is rsync.

The basic syntax I always successfully use is the following:

rsync -avh /home/user/Documents /media/user/myusbstick

Warning: if you want to copy the whole Documents folder use the syntax is ok. But if you want to copy only the file and not the folder you have to add a slash. Like this:

rsync -avh /home/user/Documents/ /media/user/myusbstick

Of course if you want to copy a file:

rsync -avh /home/user/Documents/file1 /media/user/myusbstick

for multiple files

rsync -avh /home/user/Documents/file1 /home/user/Documents/file2 /media/user/myusbstick

The syntax works for any folder/file you want to copy.

I'm aware this is not the real solution, but it's an easy and safe way to avoid annoying issues.

Answer 3

Old question, but it seems as though the problem still comes up. Setting the buffer to 15MB as suggested here did not work on Ubuntu 19.04, and brought my system to a grinding halt.

I was trying to copy a 1.5GB file onto an empty (newly formatted) FAT32 16GB drive. I let it run for about 10 minutes just to see if it would finish, with no luck.

Reformatting to NTFS let the operation finish in less than 10 seconds. I don't know why this would matter because FAT32 should allow any single file with size under 4GB, but it seemed to work just fine. Not an ideal fix for drives you want to use with MacOS, but an easy workaround for all other use cases. I imagine exFAT would have worked similarly, but I did not test it.