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ArON

Member

Registered: 2018-11-06

Posts: 13

[SOLVED]Thunar mounts USB drives with (false?) root permission

Hi,

I found out a weird behaviour of thunar (or thunar-volman?), which can be duplicated on both Xubuntu and Arch, with several USB ports on several computers.

Here are the steps to duplicate this problem:

a) After a reboot, plug in a USB stick (or USB HDD or card reader), everything is fine;

Say, the USB device is at /dev/sdb, and the mount point at:
/media/my_username/USB_STICK in Xubuntu, or
/run/media/my_username/USB_STICK in Arch

It can be mounted with my_username's permission. With a mouse, you can paste files into the USB drives (or Ctrl+V).

So far, so good.

b) If this USB stick is ejected (by clicking the "eject button" in the Side Pane under DEVICES in Thunar), unplugged then plugged back in, the mount point now has a root permission.

Now with only your mouse (or Ctrl+V), you cannot paste files or create a new folder/file.

c) Enabling/Disabling Volume Management has no effect; Changing USB ports has no effect.

It means, in an home/office environment, if you plug in a USB drive, copy some files and share it with others, then when you plug this USB drive back in your PC again, you cannot copy/paste again without using terminal or rebooting the machine.

d) It doesn't seem to be a gvfs/udisk2 bug, because Nautilus always mounts correctly. Below is a screenshot of the mount point directory's property shown by the file managers.

What's odd is this: the mount point actually doesn't have root permission.

If you copy files in terminal (in Arch):

$ cp abc.txt "/run/media/my_username/USB_STICK"

It works, without requiring sudo or root permission.

Checking permission (in Arch):

ls -la "/run/media/my_username/USB_STICK"
total 32
drwxrwxrwx 1 my_username users 32768 Nov  8 15:45 .
drwxr-xr-x 4 root root     80 Nov  8 15:33 ..

"." indicates that this directory has user permission, not root.

This goes away after a reboot only for the 1st plugging in, and it reappears starting at the 2nd time you plug in the USB drive.

Is this a bug or maybe by design? If the former, how can we fix it?

Thanks!

Last edited by ArON (2019-01-25 00:40:55)

ToZ

Administrator

From: Canada

Registered: 2011-06-02

Posts: 11,481

Re: [SOLVED]Thunar mounts USB drives with (false?) root permission

What I see is that I can't copy a previously selected file after the eject and remount commands. If I re-select the file and copy it, I can then paste it. Thunar 1.8.1 on Arch. Still probably a bug. I'll see if I can test this on an earlier version of thunar (1.6 series).

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ArON

Member

Registered: 2018-11-06

Posts: 13

Re: [SOLVED]Thunar mounts USB drives with (false?) root permission

Thanks @ToZ. After reading your posts. I found out this:

a. insert the USB flash drive, copy a file into this USB drive, everything is fine.

b. eject it and then insert it again

c. Now right away I can't create a folder / file or delete a file on/from this USB drive by right click, as the menus are grayed. I can't drag and drop a file into this USB drive;

d. Then, if I copy a file elsewhere (i.e. not from this USB drive), then I'll be able to paste the file inside the USB drive, or create a file/folder, or delete a file from this USB drive.

What's odd is, in order for me to delete a file from the USB drive, I need to copy a file outside of the drive first.

P.S.
e. I have repeated the above for dozens of times, and sometimes I can't even have the same results, sometimes no matter what I do, I can't paste a file any more. So maybe a bug?

f. but this chaotic behaviour exists on 2 different Arch machines so at least this appears to be consistent.

Tested on Arch with Thunar 1.8.2 and 1.8.1.

Is this reproducible on your end? Thanks a lot!

Last edited by ArON (2018-12-05 23:11:18)

ToZ

Administrator

From: Canada

Registered: 2011-06-02

Posts: 11,481

Re: [SOLVED]Thunar mounts USB drives with (false?) root permission

I haven't bee able to test this on 1.6x, but I can replicate the issue on 1.8.x. I think you should create a bug report.

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texadactyl

Member

Registered: 2018-12-12

Posts: 1

Re: [SOLVED]Thunar mounts USB drives with (false?) root permission

This anomaly was reported in 2014 as a Xubuntu report against Thunar 1.6.3: https://bugs.launchpad.net/ubuntu/+sour … ug/1332623
The behavior is the same today in Ubuntu 18.04.1.

ToZ

Administrator

From: Canada

Registered: 2011-06-02

Posts: 11,481

Re: [SOLVED]Thunar mounts USB drives with (false?) root permission

@texadactly, according to the bug report you linked, this was an issue with gio and not thunar, and the gio bug was resolved. There is not much that Xfce can do about this.

Also according to that bug report, the fix was released in glib-2.55 which is not currently available in the current ubuntu versions. This is really something you should follow up with your distro maintainers.

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ArON

Member

Registered: 2018-11-06

Posts: 13

Re: [SOLVED]Thunar mounts USB drives with (false?) root permission

Happy to see that this is fixed today:
https://git.xfce.org/xfce/thunar/commit … 687e6fa733

Initial tests show that it's fixed (in 1.8.3 from Arch repo)! Thank you devs!