5.10.4. Creating a filesystem

Filesystems are created, i.e., initialized, with the mkfs command. There is actually a separate program for each filesystem type. mkfs is just a front end that runs the appropriate program depending on the desired filesystem type. The type is selected with the -t fstype option.

The programs called by mkfs have slightly different command line interfaces. The common and most important options are summarized below; see the manual pages for more.

• -t fstype

• Select the type of the filesystem.

• -c

• Search for bad blocks and initialize the bad block list accordingly.

• -l filename

• Read the initial bad block list from the name file.

There are also many programs written to add specific options when creating a specific filesystem. For example mkfs.ext3 adds a -b option to allow the administrator to specify what block size should be used. Be sure to find out if there is a specific program available for the filesystem type you want to use. For more information on determining what block size to use please see

Section 5.10.5

.

To create an ext2 filesystem on a floppy, one would give the following commands:

|

$ **fdformat -n /dev/fd0H1440**
Double-sided, 80 tracks, 18 sec/track. Total capacity 
1440 KB.
Formatting ... done
$ **badblocks /dev/fd0H1440 1440 >
$ **mkfs.ext2 -l bad-blocks 
/dev/fd0H1440**
mke2fs 0.5a, 5-Apr-94 for EXT2 FS 0.5, 94/03/10
360 inodes, 1440 blocks
72 blocks (5.00%) reserved for the super user
First data block=1
Block size=1024 (log=0)
Fragment size=1024 (log=0)
1 block group
8192 blocks per group, 8192 fragments per group
360 inodes per group

Writing inode tables: done
Writing superblocks and filesystem accounting information: 
done
$

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First, the floppy was formatted (the -n option prevents validation, i.e., bad block checking). Then bad blocks were searched with badblocks, with the output redirected to a file, bad-blocks. Finally, the filesystem was created, with the bad block list initialized by whatever badblocks found.

The -c option could have been used with mkfs instead of badblocks and a separate file. The example below does that.

|

$ **mkfs.ext2 -c 
/dev/fd0H1440**
mke2fs 0.5a, 5-Apr-94 for EXT2 FS 0.5, 94/03/10
360 inodes, 1440 blocks
72 blocks (5.00%) reserved for the super user
First data block=1
Block size=1024 (log=0)
Fragment size=1024 (log=0)
1 block group
8192 blocks per group, 8192 fragments per group
360 inodes per group

Checking for bad blocks (read-only test): done
Writing inode tables: done
Writing superblocks and filesystem accounting information: 
done
$

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The -c option is more convenient than a separate use of badblocks, but badblocks is necessary for checking after the filesystem has been created.

The process to prepare filesystems on hard disks or partitions is the same as for floppies, except that the formatting isn't needed.