When building a target filesystem, it is desirable to not have to
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become root and then run 'mknod' a thousand times. Using a device
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table you can create device nodes and directories "on the fly".
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You can do all sorts of interesting things with a device table file.
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For example, if you want to adjust the permissions on a particular
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file you can just add an entry like:
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/sbin/foobar f 2755 0 0 - - - - -
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and (assuming the file /sbin/foobar exists) it will be made setuid
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root (regardless of what its permissions are on the host filesystem.
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Furthermore, you can use a single table entry to create a many device
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minors. For example, if I wanted to create /dev/hda and
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/dev/hda[0-15] I could just use the following two table entries:
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/dev/hda b 640 0 0 3 0 0 0 -
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/dev/hda b 640 0 0 3 1 1 1 15
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Device table entries take the form of:
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<name> <type> <mode> <uid> <gid> <major> <minor> <start> <inc> <count>
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where name is the file name, type can be one of:
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f: A regular file
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d: Directory
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c: Character special device file
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b: Block special device file
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p: Fifo (named pipe)
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uid is the user id for the target file, gid is the group id for the
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target file. The rest of the entries (major, minor, etc) apply only
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to device special files.
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