How to get Btrfs on 2nd partition of USB HDD to automount as read/write

["dg1727" <dg1727@hushmail.com>]

Hello, 

The question below is based on 
https://lists.ubuntu.com/archives/xubuntu-users/2012-
August/004509.html

Thanks in advance for any help with the following question, 
including pointing me to some other info resource if needed.  

I have a user with an Xubuntu 12.04.1 laptop, 32-bit.  He needs to 
use a USB hard disk drive which has 2 partitions:  the 1st 
partition is NTFS and the 2nd partition is Btrfs.  

When he plugs in the hard drive, both partitions auto-mount OK, 
except that the Btrfs partition automounts read-only.  That is, the 
permissions of the directories in /dev are drwx------ for the NTFS 
and dr-xr-xr-x for the Btrfs.  

How can the OS be set up so that the Btrfs will automount 
read/write?  

The "dmesg" command shows the following on plug-in of the drive:  

[ 7253.520087] usb 2-4: new high-speed USB device number 11 using 
ehci_hcd
[ 7253.656344] scsi11 : usb-storage 2-4:1.0
[ 7256.651677] scsi 11:0:0:0: Direct-Access     TOSHIBA  External 
USB 3.0 0001 PQ: 0 ANSI: 6
[ 7256.654722] sd 11:0:0:0: Attached scsi generic sg2 type 0
[ 7256.656970] sd 11:0:0:0: [sdb] 1465149168 512-byte logical 
blocks: (750 GB/698 GiB)
[ 7256.660515] sd 11:0:0:0: [sdb] Write Protect is off
[ 7256.660534] sd 11:0:0:0: [sdb] Mode Sense: 1f 00 00 08
[ 7256.662509] sd 11:0:0:0: [sdb] No Caching mode page present
[ 7256.662523] sd 11:0:0:0: [sdb] Assuming drive cache: write 
through
[ 7256.668478] sd 11:0:0:0: [sdb] No Caching mode page present
[ 7256.668498] sd 11:0:0:0: [sdb] Assuming drive cache: write 
through
[ 7256.673838]  sdb: sdb1 sdb2
[ 7256.681474] sd 11:0:0:0: [sdb] No Caching mode page present
[ 7256.681493] sd 11:0:0:0: [sdb] Assuming drive cache: write 
through
[ 7256.681507] sd 11:0:0:0: [sdb] Attached SCSI disk
[ 7257.545702] device label partition_label devid 1 transid 19 
/dev/sdb2
[ 7257.546790] btrfs: disk space caching is enabled

Neither the "usbmount" nor "pmount" packages are installed, but 
"thunar-volman" is installed.  I did install "pmount" only to find 
that it appears to be meant to be invoked manually, so I un-
installed it again.  

"uname -rv" reports:  

 3.2.0-29-generic #46-Ubuntu SMP Fri Jul 27 17:04:05 UTC 2012

The "groups" command shows that the user is a member of the 
following (in addition to a group named after his username):  

 adm dialout fax cdrom floppy tape sudo dip video plugdev fuse 
lpadmin sambashare

The "mount" command shows for the Btrfs partition in question:  

 /dev/sdb2 on /media/[partition_label] type btrfs 
(rw,nosuid,nodev,uhelper=udisks)

(I have substituted [partition_label] for the partition label, 
which is all letters, no punctuation marks.)

Because "mount" shows "rw", does that mean that it is the 
configuration of Btrfs, not the configuration of automounting, that 
is at issue?  

Thanks again for any suggestions.  

-dg1727