#mkfs -t ext3 /tmp/disk10g.img

mke2fs 1.41.12 (17-May-2010)
/tmp/disk10g.img is not a block special device.
Proceed anyway? (y,n) y
warning: Unable to get device geometry for /tmp/disk10g.img
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
640848 inodes, 2560000 blocks
128000 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2621440000
79 block groups
32768 blocks per group, 32768 fragments per group
8112 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 34 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

mke2fs 1.41.12 (17-May-2010)
/tmp/disk10g.img is not a block special device.
Proceed anyway? (y,n) y
warning: Unable to get device geometry for /tmp/disk10g.img
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
640848 inodes, 2560000 blocks
128000 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2621440000
79 block groups
32768 blocks per group, 32768 fragments per group
8112 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 34 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.