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Thread: Determine is filesystem is Etx2 or Ext3 or Ext4?

  1. #1
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    Question Determine is filesystem is Etx2 or Ext3 or Ext4?

    Hello.

    How can i correctly determine the type of fyle system? What fields i should compare? As i understand,it is imposible to do this by revision_level field from superblock =\ Any ideas?...

    Thanks.

  2. #2
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    Re: Determine is filesystem is Etx2 or Ext3 or Ext4?

    If it's mounted, you should be able to get the filesystem type from a plain mount command. First line of mine is:

    $ mount
    /dev/sda1 on / type ext3 (rw,relatime,errors=remount-ro)

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    Re: Determine is filesystem is Etx2 or Ext3 or Ext4?

    Quote Originally Posted by DanielWaterworth View Post
    If it's mounted, you should be able to get the filesystem type from a plain mount command. First line of mine is:

    $ mount
    /dev/sda1 on / type ext3 (rw,relatime,errors=remount-ro)
    Hm. And how i can do it except this? Just have superblock fields values and other technical information. I mean, i have a some hex editor and i can waching through the file system. How can i resolve the type?)

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    Re: Determine is filesystem is Etx2 or Ext3 or Ext4?

    What is wrong with running mount - or something like that ?
    Tony - Happy to try to help.
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  5. #5
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    Re: Determine is filesystem is Etx2 or Ext3 or Ext4?

    I don't think there is a simple way to do this (like looking at a specific byte in the superblock).
    You can use blkid or file -s without having to mount the partition.
    5127d464-4548-4993-a138-f546f2fd2a33

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    Re: Determine is filesystem is Etx2 or Ext3 or Ext4?

    'blkid', 'mount', 'cat /proc/mounts' are all good ways

    Another is 'cd /proc/fs' or 'cd /sys/fs' and look around (the devices will be listed under the filesystem type).

    'tune2fs -l <device>' is the best way to tell absolutely. It will tell you the filesystem magic number. Unfortunately, then you've got to figure out what filesystem that corresponds to. (This is how the system actually knows what filesystem it is. However, you can also tell by glancing at the filesystem features.
    Favorite man page quote: "The backreference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression." [excerpt from grep(1)]

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    Re: Determine is filesystem is Etx2 or Ext3 or Ext4?

    Ugh... looking at /etc/fstab doesn't seem a bad idea if the filesystem is internal.

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    Re: Determine is filesystem is Etx2 or Ext3 or Ext4?

    Ugh... fstab is user-generated and not authoritative. In other words, it could be wrong.
    Favorite man page quote: "The backreference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression." [excerpt from grep(1)]

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    Re: Determine is filesystem is Etx2 or Ext3 or Ext4?

    'tune2fs -l <device>' is the best way to tell absolutely. It will tell you the filesystem magic number.

    It does not work for me. I have the same magic numbers for different filesystems.
    Code:
    arrange@lucid-lean:~$ sudo tune2fs -l /dev/sdb2 | grep magic
    Filesystem magic number:  0xEF53
    arrange@lucid-lean:~$ sudo tune2fs -l /dev/sdb1 | grep magic
    Filesystem magic number:  0xEF53
    arrange@lucid-lean:~$ sudo blkid /dev/sdb2
    /dev/sdb2: LABEL="hh" UUID="87435c1d-6517-4c85-b68d-2841ae91fa43" SEC_TYPE="ext2" TYPE="ext3" 
    arrange@lucid-lean:~$ sudo blkid /dev/sdb1
    /dev/sdb1: LABEL="Dokumenty" UUID="304a520a-0a97-4f94-abe1-a8fc6858040a" TYPE="ext4"
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    Re: Determine is filesystem is Etx2 or Ext3 or Ext4?

    Quote Originally Posted by arrange View Post
    'tune2fs -l <device>' is the best way to tell absolutely. It will tell you the filesystem magic number.

    It does not work for me. I have the same magic numbers for different filesystems.
    Code:
    arrange@lucid-lean:~$ sudo tune2fs -l /dev/sdb2 | grep magic
    Filesystem magic number:  0xEF53
    arrange@lucid-lean:~$ sudo tune2fs -l /dev/sdb1 | grep magic
    Filesystem magic number:  0xEF53
    arrange@lucid-lean:~$ sudo blkid /dev/sdb2
    /dev/sdb2: LABEL="hh" UUID="87435c1d-6517-4c85-b68d-2841ae91fa43" SEC_TYPE="ext2" TYPE="ext3" 
    arrange@lucid-lean:~$ sudo blkid /dev/sdb1
    /dev/sdb1: LABEL="Dokumenty" UUID="304a520a-0a97-4f94-abe1-a8fc6858040a" TYPE="ext4"
    It seems I have an incorrect understanding of the magic number -- it does not distinguish between different ext filesystems. I have confirmed this on my own systems (both a system using the ext4 driver for all ext systems and another system that does not do this).

    Disregard what I said about using the magic number for this purpose. (I think you can still use to type filesystems, but not to distinguish between ext sub-types.) Sorry for the confusion.
    Last edited by BoneKracker; June 12th, 2010 at 04:25 PM.
    Favorite man page quote: "The backreference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression." [excerpt from grep(1)]

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