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I want to mount a partition to an auxiliary folder via mount to fix a damaged grub.

I used the command.

sudo mount /dev/sdb2 /home/ubuntu/temp

and got as error:

mount: you must specify the filesystem type

Why?

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4 Answers 4

up vote 16 down vote accepted

You need to add the -t FILESYSTEMTYPE argument to the command, replacing FILESYSTEMTYPE with your filesystem type. This specifies the filesystem type of the filesystem to be mounted. In your case, this would be /dev/sdb2. Some common, valid filesystem types are:

  • auto - this is a special one. It will try to guess the fs type when you use this.
  • ext4 - this is probably the most common Linux fs type of the last few years
  • ext3 - this is the most common Linux fs type from a couple years back
  • ntfs - this is the most common Windows fs type or larger external hard drives
  • vfat - this is the most common fs type used for smaller external hard drives
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3  
But normally, it will guess the correct filesystem. I don't think I usually need to specify the file system type. There may be some other problem preventing it from recognizing the type in this case. –  Marty Fried May 29 '12 at 16:25
    
Given that the OP seems to be trying to fix a damaged filesystem, it may not be detected correctly. –  reverendj1 May 29 '12 at 16:44
    
I only see a damaged grub configuration, with a UUID that doesn't exist; but what I was gettting at is to suggest that this may not be the problem (not so much for you as for the OP). The problem may well be something like an incorrect partition specifier, but I didn't want to get too detailed because his question was not well done (note he didn't even specify the mount command at all), plus he's already started other topics on the subject, it seems. I didn't want him to be too surprised if it still didn't work. –  Marty Fried May 29 '12 at 16:52

I was getting a similar error:

# mount /dev/sdb1 /mydisk/ -t auto
mount: you must specify the filesystem type

I tried finding out the issue and the issue was, I had partitioned it but no filesystem was assigned.

# mkfs.ext3 /dev/sdb1 2>/dev/null
...
Superblock backups stored on blocks: 
...
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 39 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override

After this it successfully got mounted.

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Please use parted -l to check the partition type and make sure you are mounting an actual data partition with known partition types (for example, ntfs, fat, etc).

Here is what you would see from an 8TB drive, the first partition is not the actual data partition and instead, you should mount the second partition, which is the actual data partition.

Model: TRUSTED Mass Storage (scsi)

Disk /dev/sdb: 8796GB

Sector size (logical/physical): 512B/512B

Partition Table: gpt

Number Start End Size File system Name Flags

1 17.4kB 134MB 134MB Microsoft reserved partition msftr es

2 134MB 8796GB 8796GB ntfs Basic data partition

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There is more to the story here. Usually if you mount a partition with a common filesystem type using mount, it will auto-detect the partition type.

The fact that it isn't auto-detecting it in this case could signal a few possibilities.

  • You haven't installed filesystem tools for the chosen filesystem. If you did a standard desktop install of Ubuntu, this shouldn't normally be a problem.

    For example, to mount ntfs drives in recent versions of Ubuntu you need the ntfs-3g package.

  • You selected the wrong partition.

  • The partition is corrupt or unformatted. In this case, you should probably do a filesystem check (fsck) on it before mounting it. You may then want to proceed to mount it manually, specifying the filesystem type, as read-only. If all else fails you may need special recovery software such as testdisk.

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