Fedora 13 mount Error Solved

I recently upgraded to Fedora 13(and was quite pleased) only to discover my backup SATA drive would not mount.  I got the generic, ‘mount: /dev/sdb1 already mounted or /home/matt/backup busy’ error message.  Hours of googling and one reinstall later I solved the problem.

Goals of this Post:

– Fix SATA drive mount error: mount: /dev/sdb1 already mounted or /home/matt/backup busy

I did a clean install, but before hand I copied all my important data to my backup disk.  I was disappointed because recently I had to deal with several driver issues in the Window 7 installation process… and now Linux…  

I tried to mount my FAT32 partition to recover my old files, but kept getting this error: mount error: “mount: /dev/sdb1 already mounted or /home/matt/backup busy”.

This is a fairly common error message.  You will see this message as a ‘evms(Enterprise Volume Management System) bug’ in Unbuntu or if you don’t have the module for said file system(like NTFS, FAT, ext4, etc…). I spent several hours wrestling with this issue before I discovered the culprit.

[root@mattcom ~]# mount -t vfat /dev/sdb1 /home/matt/backup
mount: /dev/sdb1 already mounted or /home/matt/backup busy

So I checked to that if the disk was mounted,

[root@mattcom ~]# df -H
Filesystem             Size   Used  Avail Use% Mounted on
/dev/sda2               72G   4.1G    64G   7% /
tmpfs                  1.8G   709k   1.8G   1% /dev/shm
/dev/sda1              204M    24M   170M  13% /boot
[root@mattcom ~]#

The disk was not mounted, so I checked fdisk…

[root@mattcom ~]# fdisk -l

Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000112e6

Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          26      204800   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              26        8822    70656000   83  Linux
/dev/sda3            8822        9730     7288832   82  Linux swap / Solaris

Disk /dev/sdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0002b779

Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       19457   156288321    c  W95 FAT32 (LBA)

My partition was there as expected.  So I decided to check my boot.log just in case I had missed something.

[root@mattcom ~]# cat /var/log/boot.log
Welcome to Fedora
Press ‘I’ to enter interactive startup.
Starting udev:                                             [  OK  ]
Setting hostname mattcom:                                  [  OK  ]
Setting up Logical Volume Management:   /dev/md126: read failed after 0 of 4096 at 0: Input/output error
No volume groups found  [  OK  ]
Checking filesystems
/dev/sda2: clean, 122201/4423680 files, 1158068/17664000 blocks
/dev/sda1: clean, 36/51200 files, 29315/204800 blocks   [  OK  ]

My boot log showed a ‘Input/output error’ on ‘/dev/md126’. I read a post in my googling that suggested the ‘fsarchiver’ tool.  It also showed the mysterious ‘/dev/md126’.

I thought it was possible that Linux was thinking my SATA drive was part of a RAID array.  So I used the ‘mdadm’ tool to check.

[root@mattcom ~]# cat /proc/mdstat
Personalities :
md126 : inactive sdb[0]
156288642 blocks super external:/md127/0

md127 : inactive sdb[0](S)
2257 blocks super external:imsm

unused devices: <none>

[root@mattcom ~]# mdadm –stop /dev/md126
[root@mattcom ~]# mdadm –stop /dev/md127

[root@mattcom ~]# mount -t vfat /dev/sdb1 /home/matt/backup
[root@mattcom ~]#

Success!  Once I stopped the RAID devices /dev/sdb1 was mount

By now I was convinced that that the dmraid driver had flagged my disk as part of a RAID array

I found the answer at the mdadm WIKI page, http://en.wikipedia.org/wiki/Mdadm

mdadm –zero-superblock /dev/sdb

Now everything boots fine and the hard drive can mount normally!  I hope this article helps someone else.


  • Mark Sheppard

    Thanks for sharing this – most useful!

    I managed to make my system unbootable and when I tried to recover from a rescue disk it wasn’t letting me mount or even fsck the root partition. Turned out that dmraid had picked up some old unused software raid signatures on the disks and automatically set that up. After erasing the signatures I can now access my root partition from the rescue disk.

    Comment | November 4, 2010
  • mattb

    Awome I’m glad my struggles helped point you the right direction!

    Comment | November 8, 2010

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