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user5950
Asked: 2013-01-26 05:53:06 +0800 CST

Automounted USB devices are read only

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Since I upgraded to Ubuntu 12.10 the automout of USB devices does not work as expected. When I plug in a storage device it is recognized correctly but I do not have write privileges on it. I thought, that maybe the permissions of /media are not correctly set, but I don't know, how they have to be. They are like this:

drwxr-xr-x  14 root  root   4096 Jan 13 19:37 media

I also checked whether my user is a member of the group plugdev and he definitely is.

What else could be the cause of that problem?

Update: Here is the dmesg output after plugging in an USB storage device: http://pastebin.com/pJ7qebQR

usb

6 Answers

  1. I think you are suffering the bug #1021375

    You can workaround it by renaming the folder ~/.config/nautilus and then logout and log back in.

    1. mv ~/.config/nautilus ~/.config/nautilus-bak
    2. Logout.
    3. Login.
    • 36 
  2. sudo mount -o remount,rw /media/MonterFolderName

    This shall solve the issue. I am not sure how to make it permanent. I am not sure if chmod would work if in case the USB is not mounted in readwrite mode in the first place.

    Tested on Ubuntu 12.10 and 13.

    • 21

  3. When the USB is inserted it's mounted on /media/<username> that you should have permissions through an access control list.

    You can check what the permissions are e.g.

    bcbc@23:34:50:~$ getfacl /media/bcbc
# file: media/bcbc
# owner: root
# group: root
user::rwx
user:bcbc:r-x
group::---
mask::r-x
other::---

    If there is no access control list, just delete the directory and it will recreate it with the correct permissions.

    sudo rmdir /media/<username>

    Or add the ACL:

    sudo setfacl -m u:<username>:rx /media/<username>
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  4. Problem appears to have gone away

    This is a 5 y/o question on short term release Ubuntu 12.10. The dmesg link is no longer available in the OP's question. But if I plug in a Ubuntu 18.04 Live USB with persistent storage dmesg reveals:

    $ dmesg | tail -n18
[115528.249547] usb-storage 1-9:1.0: USB Mass Storage device detected
[115528.250152] scsi host2: usb-storage 1-9:1.0
[115528.250474] usbcore: registered new interface driver usb-storage
[115528.255685] usbcore: registered new interface driver uas
[115529.281407] scsi 2:0:0:0: Direct-Access     Verbatim STORE N GO       PMAP PQ: 0 ANSI: 6
[115529.282090] sd 2:0:0:0: Attached scsi generic sg1 type 0
[115529.992200] sd 2:0:0:0: [sdb] 30261248 512-byte logical blocks: (15.5 GB/14.4 GiB)
[115529.992998] sd 2:0:0:0: [sdb] Write Protect is off
[115529.993006] sd 2:0:0:0: [sdb] Mode Sense: 23 00 00 00
[115529.993787] sd 2:0:0:0: [sdb] No Caching mode page found
[115529.993797] sd 2:0:0:0: [sdb] Assuming drive cache: write through
[115530.592616]  sdb: sdb1 sdb2 sdb3 sdb4 sdb5
[115530.596279] sd 2:0:0:0: [sdb] Attached SCSI removable disk
[115531.018019] EXT4-fs (sdb5): warning: mounting unchecked fs, running e2fsck is recommended
[115531.470201] EXT4-fs (sdb5): mounted filesystem without journal. Opts: (null)
[115531.480738] ISO 9660 Extensions: Microsoft Joliet Level 3
[115531.483397] ISO 9660 Extensions: Microsoft Joliet Level 3
[115531.512219] ISO 9660 Extensions: RRIP_1991A

    Unlike OP implies, there is no warning for read-only. Notice the line:

    sd 2:0:0:0: [sdb] Write Protect is off

    Apparently whatever the problem was 5 years ago, it no longer exists today under Ubuntu 16.04 LTS. Also for the only other LTS version today, 14.04 I can't remember this being a problem either. Only SD RAM cards come to mind as being read only, which is a different problem altogether.

    • 2

  5. Nothing is wrong with the mounting options and fstab file, as far as my knowledge, you just have to use below command to get the Required right permissions on the media folder. and I will explain you why.

    1) your current permissions on the folder as you mentioned are as below. (Apologize if you know this and I'm bothering you with it.)

    drwxr-xr-x 14 root root 4096 Jan 13 19:37 media in this d stands for directory, first group of rwx stands for the rights of the user who owns that object, which is in your case root.

    second group of rwx stands for the rights of the group who owns that object & here you have only r-x which means even if you are in the sudoers file or in the admin group you do not have rights to write in it.

    Third group of rwx is or other users, who are not owner of that object nor in the group who has ownership rights of that object. if your case it is again r-x only. so that is why you do not have write permissions on it.

    2) So you need to change permissions of the media folder. (I am going to consider that you are in admin group or sudoers file, because this will work only in that case). so this is what you need to do.

    $ sudo chmod -R 775 /media

    3) This will give you required write permissions on the all auto mounted drives.

    Please check and let me know if this does not work will tell you what else can be done to fix this issue.

    • 1

  6. I hit this problem too, in my case it was a fat32 corruption problem allowing to read it but not to write.

    Then if your usb key is a fat32, it might be that your filesyste is corrupted.

    To verify do a sudo dmesg

    [17183.485565] FAT-fs (sdc1): error, corrupted directory (invalid entries)
[17205.406905] FAT-fs (sdc1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.

    then unmout it, sudo fsck.vfat your_device_partition it then mount it again.

    in my specific case :

    sudo fsck.vfat /dev/sdc1
fsck.fat 4.1 (2017-01-24)
0x41: Dirty bit is set. Fs was not properly unmounted and some data may be     corrupt.
1) Remove dirty bit
2) No action
? 1
/T90bis
 Start does point to root directory. Deleting dir. 
Reclaimed 93 unused clusters (1523712 bytes).
Free cluster summary wrong (1248506 vs. really 1248599)
1) Correct
2) Don't correct
? 1
Perform changes ? (y/n) y
/dev/sdc1: 916 files, 704527/1953126 clusters
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