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How do I determine the block size of an ext3 partition on Linux?

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# tune2fs -l /dev/sda1 | grep -i 'block size'
Block size:               1024

Replace /dev/sda1 with the partition you want to check.

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Without root, without writing, and for any filesystem type, you can do:

stat -fc %s .

This will give block size of the filesystem mounted in current directory (or any other directory specified instead of the dot).

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    Don't forget the dot at the end of that command as stat -f is expecting is expecting a folder to give you stats about. – BeowulfNode42 Jan 9 '17 at 0:11
  • And to further narrow it down to what the OP asked for: stat --printf='%s' -f . – Jani Uusitalo May 19 '17 at 15:01
  • with newlinestat --printf='%s\n' -f . – c4f4t0r Mar 28 '18 at 9:48
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    @JaniUusitalo, @c4f4t0r: thanks for the hint, corrected the answer using -c which is simpler than --printf='...\n' – mik Mar 28 '18 at 14:14
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dumpe2fs -h /dev/md2

will output something with:

Block size:               4096
Fragment size:            4096
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On x86, a filesystem block is just about always 4KiB - the default size - and never larger than the size of a memory page (which is 4KiB).

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  • This is the same on every platform, the largest block size is supported by ext2/3 is 4096 bytes. – Dave Cheney Jun 23 '09 at 10:06
  • Thanks Dave! I learned something today ;-) I originally thought the ext3 blocksize could be 8k on platforms that supported 8k memory pages. – wzzrd Jun 23 '09 at 12:44
  • Wikipedia says it can be 8k: en.wikipedia.org/wiki/Ext3#Size_limits – dfrankow Apr 25 '12 at 22:41
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    @dfrankow: if you have 8k memory pages, such as on Alpha hardware, yes. But you do not have those on x86 hardware and that is what I was talking about. – wzzrd Apr 26 '12 at 8:03
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In the case where you don't have the right to run tune2fs on a device (e.g. in a corporate environment) you can try writing a single byte to a file on the partition in question and check the disk usage:

echo 1 > test
du -h test
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To detect block size of required partition:

  1. Detect partition name:

    $ df -h

    for example we have /dev/sda1

  2. Detect block size for this partition:

    $ sudo blockdev --getbsz /dev/sda1
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stat <<Filename>>

will also give file size in blocks

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  • This is not what the OP asked – Pablo A Jul 3 '19 at 7:55
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Use

sudo dumpe2fs /dev/sda1 | grep "Block size"

where /dev/sda1 is the device partition. You can get it from lsblk

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